Descartes--Discourse on the Method of Rightly Conducting the Reason, and Seeking Truth in the Sciences

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DISCOURSE ON THE METHOD OF RIGHTLY CONDUCTING THE REASON, AND SEEKING TRUTH IN THE SCIENCES  by Rene Descarte. 

Descartes contributed a towering amount in the history of science and in establishing modern Western philosophy, all accomplished in a relatively short period of time, as Descartes for all of his massive output only lived to be 54 (1596-1650)...and most of that was completed between 1630 and 1650.  Twenty years. Outstanding. 

René Descartes. Engraving by Jacques Lubin, after Frans Hals (via Houghton Library blog, here).

"PREFATORY NOTE BY THE AUTHOR

If this Discourse appear too long
to be read at once, it may be divided into six Parts: and, in the first, will
be found various considerations touching the Sciences; in the second, the
principal rules of the Method which the Author has discovered, in the third,
certain of the rules of Morals which he has deduced from this Method; in the
fourth, the reasonings by which he establishes the existence of God and of the
Human Soul, which are the foundations of his Metaphysic; in the fifth, the
order of the Physical questions which he has investigated, and, in particular,
the explication of the motion of the heart and of some other difficulties
pertaining to Medicine, as also the difference between the soul of man and that
of the brutes; and, in the last, what the Author believes to be required in order
to greater advancement in the investigation of Nature than has yet been made,
with the reasons that have induced him to write.

PART 1

Good sense is, of all things among men, the most equally distributed; for every one thinks himself so abundantly
provided with it, that those even who are the most difficult to satisfy in everything else, do not usually desire a larger measure of this quality than they already possess. And in this it is not likely that all are mistaken the
conviction is rather to be held as testifying that the power of judging aright and of distinguishing truth from error, which is properly what is called good sense or reason, is by nature equal in all men; and that the diversity of our
opinions, consequently, does not arise from some being endowed with a larger share of reason than others, but solely from this, that we conduct our thoughts along different ways, and do not fix our attention on the same objects. For to be possessed of a vigorous mind is not enough; the prime requisite is rightly to apply it. The greatest minds, as they are capable of the highest excellences, are open likewise to the greatest aberrations; and those who travel very slowly may yet make far greater progress, provided they keep always to the straight road, than those who, while they run, forsake it.

For myself, I have never fancied
my mind to be in any respect more perfect than those of the generality; on the
contrary, I have often wished that I were equal to some others in promptitude
of thought, or in clearness and distinctness of imagination, or in fullness and
readiness of memory. And besides these, I know of no other qualities that
contribute to the perfection of the mind; for as to the reason or sense,
inasmuch as it is that alone which constitutes us men, and distinguishes us
from the brutes, I am disposed to believe that it is to be found complete in
each individual; and on this point to adopt the common opinion of philosophers,
who say that the difference of greater and less holds only among the accidents,
and not among the forms or natures of individuals of the same species.

I will not hesitate, however, to
avow my belief that it has been my singular good fortune to have very early in
life fallen in with certain tracks which have conducted me to considerations
and maxims, of which I have formed a method that gives me the means, as I
think, of gradually augmenting my knowledge, and of raising it by little and
little to the highest point which the mediocrity of my talents and the brief
duration of my life will permit me to reach. For I have already reaped from it
such fruits that, although I have been accustomed to think lowly enough of
myself, and although when I look with the eye of a philosopher at the varied
courses and pursuits of mankind at large, I find scarcely one which does not
appear in vain and useless, I nevertheless derive the highest satisfaction from
the progress I conceive myself to have already made in the search after truth,
and cannot help entertaining such expectations of the future as to believe that
if, among the occupations of men as men, there is any one really excellent and
important, it is that which I have chosen.

After all, it is possible I may be
mistaken; and it is but a little copper and glass, perhaps, that I take for
gold and diamonds. I know how very liable we are to delusion in what relates to
ourselves, and also how much the judgments of our friends are to be suspected
when given in our favor. But I shall endeavor in this discourse to describe the
paths I have followed, and to delineate my life as in a picture, in order that
each one may also be able to judge of them for himself, and that in the general
opinion entertained of them, as gathered from current report, I myself may have
a new help towards instruction to be added to those I have been in the habit of
employing.

My present design, then, is not to
teach the method which each ought to follow for the right conduct of his
reason, but solely to describe the way in which I have endeavored to conduct my
own. They who set themselves to give precepts must of course regard themselves
as possessed of greater skill than those to whom they prescribe; and if they
err in the slightest particular, they subject themselves to censure. But as
this tract is put forth merely as a history, or, if you will, as a tale, in
which, amid some examples worthy of imitation, there will be found, perhaps, as
many more which it were advisable not to follow, I hope it will prove useful to
some without being hurtful to any, and that my openness will find some favor
with all.

From my childhood, I have been
familiar with letters; and as I was given to believe that by their help a clear
and certain knowledge of all that is useful in life might be acquired, I was
ardently desirous of instruction. But as soon as I had finished the entire
course of study, at the close of which it is customary to be admitted into the
order of the learned, I completely changed my opinion. For I found myself
involved in so many doubts and errors, that I was convinced I had advanced no farther
in all my attempts at learning, than the discovery at every turn of my own
ignorance. And yet I was studying in one of the most celebrated schools in
Europe, in which I thought there must be learned men, if such were anywhere to
be found. I had been taught all that others learned there; and not contented
with the sciences actually taught us, I had, in addition, read all the books
that had fallen into my hands, treating of such branches as are esteemed the
most curious and rare. I knew the judgment which others had formed of me; and I
did not find that I was considered inferior to my fellows, although there were
among them some who were already marked out to fill the places of our
instructors. And, in fine, our age appeared to me as flourishing, and as fertile
in powerful minds as any preceding one. I was thus led to take the liberty of
judging of all other men by myself, and of concluding that there was no science
in existence that was of such a nature as I had previously been given to
believe.

I still continued, however, to
hold in esteem the studies of the schools. I was aware that the languages
taught in them are necessary to the understanding of the writings of the
ancients; that the grace of fable stirs the mind; that the memorable deeds of
history elevate it; and, if read with discretion, aid in forming the judgment;
that the perusal of all excellent books is, as it were, to interview with the
noblest men of past ages, who have written them, and even a studied interview,
in which are discovered to us only their choicest thoughts; that eloquence has
incomparable force and beauty; that poesy has its ravishing graces and
delights; that in the mathematics there are many refined discoveries eminently
suited to gratify the inquisitive, as well as further all the arts an lessen
the labour of man; that numerous highly useful precepts and exhortations to
virtue are contained in treatises on morals; that theology points out the path
to heaven; that philosophy affords the means of discoursing with an appearance of
truth on all matters, and commands the admiration of the more simple; that
jurisprudence, medicine, and the other sciences, secure for their cultivators
honors and riches; and, in fine, that it is useful to bestow some attention
upon all, even upon those abounding the most in superstition and error, that we
may be in a position to determine their real value, and guard against being
deceived.

But I believed that I had already
given sufficient time to languages, and likewise to the reading of the writings
of the ancients, to their histories and fables. For to hold converse with those
of other ages and to travel, are almost the same thing. It is useful to know
something of the manners of different nations, that we may be enabled to form a
more correct judgment regarding our own, and be prevented from thinking that
everything contrary to our customs is ridiculous and irrational, a conclusion
usually come to by those whose experience has been limited to their own
country. On the other hand, when too much time is occupied in traveling, we
become strangers to our native country; and the over curious in the customs of
the past are generally ignorant of those of the present. Besides, fictitious
narratives lead us to imagine the possibility of many events that are impossible;
and even the most faithful histories, if they do not wholly misrepresent
matters, or exaggerate their importance to render the account of them more
worthy of perusal, omit, at least, almost always the meanest and least striking
of the attendant circumstances; hence it happens that the remainder does not
represent the truth, and that such as regulate their conduct by examples drawn
from this source, are apt to fall into the extravagances of the knight-errants
of romance, and to entertain projects that exceed their powers.

I esteemed eloquence highly, and
was in raptures with poesy; but I thought that both were gifts of nature rather
than fruits of study. Those in whom the faculty of reason is predominant, and
who most skillfully dispose their thoughts with a view to render them clear and
intelligible, are always the best able to persuade others of the truth of what
they lay down, though they should speak only in the language of Lower Brittany,
and be wholly ignorant of the rules of rhetoric; and those whose minds are
stored with the most agreeable fancies, and who can give expression to them
with the greatest embellishment and harmony, are still the best poets, though
unacquainted with the art of poetry.

I was especially delighted with
the mathematics, on account of the certitude and evidence of their reasonings;
but I had not as yet a precise knowledge of their true use; and thinking that
they but contributed to the advancement of the mechanical arts, I was
astonished that foundations, so strong and solid, should have had no loftier
superstructure reared on them. On the other hand, I compared the disquisitions
of the ancient moralists to very towering and magnificent palaces with no
better foundation than sand and mud: they laud the virtues very highly, and
exhibit them as estimable far above anything on earth; but they give us no
adequate criterion of virtue, and frequently that which they designate with so
fine a name is but apathy, or pride, or despair, or parricide.

I revered our theology, and
aspired as much as any one to reach heaven: but being given assuredly to
understand that the way is not less open to the most ignorant than to the most
learned, and that the revealed truths which lead to heaven are above our
comprehension, I did not presume to subject them to the impotency of my reason;
and I thought that in order competently to undertake their examination, there
was need of some special help from heaven, and of being more than man.

Of philosophy I will say nothing,
except that when I saw that it had been cultivated for many ages by the most
distinguished men, and that yet there is not a single matter within its sphere
which is not still in dispute, and nothing, therefore, which is above doubt, I
did not presume to anticipate that my success would be greater in it than that
of others; and further, when I considered the number of conflicting opinions
touching a single matter that may be upheld by learned men, while there can be
but one true, I reckoned as well-nigh false all that was only probable.

As to the other sciences, inasmuch
as these borrow their principles from philosophy, I judged that no solid
superstructures could be reared on foundations so infirm; and neither the honor
nor the gain held out by them was sufficient to determine me to their
cultivation: for I was not, thank Heaven, in a condition which compelled me to
make merchandise of science for the bettering of my fortune; and though I might
not profess to scorn glory as a cynic, I yet made very slight account of that
honor which I hoped to acquire only through fictitious titles. And, in fine, of
false sciences I thought I knew the worth sufficiently to escape being deceived
by the professions of an alchemist, the predictions of an astrologer, the
impostures of a magician, or by the artifices and boasting of any of those who
profess to know things of which they are ignorant.

For these reasons, as soon as my
age permitted me to pass from under the control of my instructors, I entirely
abandoned the study of letters, and resolved no longer to seek any other
science than the knowledge of myself, or of the great book of the world. I
spent the remainder of my youth in traveling, in visiting courts and armies, in
holding intercourse with men of different dispositions and ranks, in collecting
varied experience, in proving myself in the different situations into which
fortune threw me, and, above all, in making such reflection on the matter of my
experience as to secure my improvement. For it occurred to me that I should
find much more truth in the reasonings of each individual with reference to the
affairs in which he is personally interested, and the issue of which must
presently punish him if he has judged amiss, than in those conducted by a man of
letters in his study, regarding speculative matters that are of no practical
moment, and followed by no consequences to himself, farther, perhaps, than that
they foster his vanity the better the more remote they are from common sense;
requiring, as they must in this case, the exercise of greater ingenuity and art
to render them probable. In addition, I had always a most earnest desire to
know how to distinguish the true from the false, in order that I might be able
clearly to discriminate the right path in life, and proceed in it with
confidence.

It is true that, while busied only
in considering the manners of other men, I found here, too, scarce any ground
for settled conviction, and remarked hardly less contradiction among them than
in the opinions of the philosophers. So that the greatest advantage I derived
from the study consisted in this, that, observing many things which, however
extravagant and ridiculous to our apprehension, are yet by common consent
received and approved by other great nations, I learned to entertain too
decided a belief in regard to nothing of the truth of which I had been
persuaded merely by example and custom; and thus I gradually extricated myself
from many errors powerful enough to darken our natural intelligence, and
incapacitate us in great measure from listening to reason. But after I had been
occupied several years in thus studying the book of the world, and in essaying
to gather some experience, I at length resolved to make myself an object of
study, and to employ all the powers of my mind in choosing the paths I ought to
follow, an undertaking which was accompanied with greater success than it would
have been had I never quitted my country or my books.

PART II

I was then in Germany, attracted
thither by the wars in that country, which have not yet been brought to a
termination; and as I was returning to the army from the coronation of the
emperor, the setting in of winter arrested me in a locality where, as I found
no society to interest me, and was besides fortunately undisturbed by any cares
or passions, I remained the whole day in seclusion, with full opportunity to
occupy my attention with my own thoughts. Of these one of the very first that
occurred to me was, that there is seldom so much perfection in works composed of
many separate parts, upon which different hands had been employed, as in those
completed by a single master. Thus it is observable that the buildings which a
single architect has planned and executed, are generally more elegant and
commodious than those which several have attempted to improve, by making old
walls serve for purposes for which they were not originally built. Thus also,
those ancient cities which, from being at first only villages, have become, in
course of time, large towns, are usually but ill laid out compared with the
regularity constructed towns which a professional architect has freely planned
on an open plain; so that although the several buildings of the former may
often equal or surpass in beauty those of the latter, yet when one observes
their indiscriminate juxtaposition, there a large one and here a small, and the
consequent crookedness and irregularity of the streets, one is disposed to
allege that chance rather than any human will guided by reason must have led to
such an arrangement. And if we consider that nevertheless there have been at
all times certain officers whose duty it was to see that private buildings
contributed to public ornament, the difficulty of reaching high perfection with
but the materials of others to operate on, will be readily acknowledged. In the
same way I fancied that those nations which, starting from a semi-barbarous
state and advancing to civilization by slow degrees, have had their laws
successively determined, and, as it were, forced upon them simply by experience
of the hurtfulness of particular crimes and disputes, would by this process
come to be possessed of less perfect institutions than those which, from the
commencement of their association as communities, have followed the
appointments of some wise legislator. It is thus quite certain that the
constitution of the true religion, the ordinances of which are derived from
God, must be incomparably superior to that of every other. And, to speak of
human affairs, I believe that the pre-eminence of Sparta was due not to the
goodness of each of its laws in particular, for many of these were very
strange, and even opposed to good morals, but to the circumstance that,
originated by a single individual, they all tended to a single end. In the same
way I thought that the sciences contained in books (such of them at least as
are made up of probable reasonings, without demonstrations), composed as they
are of the opinions of many different individuals massed together, are farther
removed from truth than the simple inferences which a man of good sense using
his natural and unprejudiced judgment draws respecting the matters of his
experience. And because we have all to pass through a state of infancy to
manhood, and have been of necessity, for a length of time, governed by our
desires and preceptors (whose dictates were frequently conflicting, while
neither perhaps always counseled us for the best), I farther concluded that it
is almost impossible that our judgments can be so correct or solid as they
would have been, had our reason been mature from the moment of our birth, and
had we always been guided by it alone.

It is true, however, that it is
not customary to pull down all the houses of a town with the single design of
rebuilding them differently, and thereby rendering the streets more handsome;
but it often happens that a private individual takes down his own with the view
of erecting it anew, and that people are even sometimes constrained to this
when their houses are in danger of falling from age, or when the foundations
are insecure. With this before me by way of example, I was persuaded that it
would indeed be preposterous for a private individual to think of reforming a
state by fundamentally changing it throughout, and overturning it in order to
set it up amended; and the same I thought was true of any similar project for
reforming the body of the sciences, or the order of teaching them established
in the schools: but as for the opinions which up to that time I had embraced, I
thought that I could not do better than resolve at once to sweep them wholly
away, that I might afterwards be in a position to admit either others more
correct, or even perhaps the same when they had undergone the scrutiny of
reason. I firmly believed that in this way I should much better succeed in the
conduct of my life, than if I built only upon old foundations, and leaned upon
principles which, in my youth, I had taken upon trust. For although I
recognized various difficulties in this undertaking, these were not, however,
without remedy, nor once to be compared with such as attend the slightest
reformation in public affairs. Large bodies, if once overthrown, are with great
difficulty set up again, or even kept erect when once seriously shaken, and the
fall of such is always disastrous. Then if there are any imperfections in the
constitutions of states (and that many such exist the diversity of
constitutions is alone sufficient to assure us), custom has without doubt
materially smoothed their inconveniences, and has even managed to steer altogether
clear of, or insensibly corrected a number which sagacity could not have
provided against with equal effect; and, in fine, the defects are almost always
more tolerable than the change necessary for their removal; in the same manner
that highways which wind among mountains, by being much frequented, become
gradually so smooth and commodious, that it is much better to follow them than
to seek a straighter path by climbing over the tops of rocks and descending to
the bottoms of precipices.

Hence it is that I cannot in any
degree approve of those restless and busy meddlers who, called neither by birth
nor fortune to take part in the management of public affairs, are yet always
projecting reforms; and if I thought that this tract contained aught which might
justify the suspicion that I was a victim of such folly, I would by no means
permit its publication. I have never contemplated anything higher than the
reformation of my own opinions, and basing them on a foundation wholly my own.
And although my own satisfaction with my work has led me to present here a
draft of it, I do not by any means therefore recommend to every one else to
make a similar attempt. Those whom God has endowed with a larger measure of
genius will entertain, perhaps, designs still more exalted; but for the many I
am much afraid lest even the present undertaking be more than they can safely
venture to imitate. The single design to strip one's self of all past beliefs
is one that ought not to be taken by every one. The majority of men is composed
of two classes, for neither of which would this be at all a befitting
resolution: in the first place, of those who with more than a due confidence in
their own powers, are precipitate in their judgments and want the patience
requisite for orderly and circumspect thinking; whence it happens, that if men
of this class once take the liberty to doubt of their accustomed opinions, and
quit the beaten highway, they will never be able to thread the byway that would
lead them by a shorter course, and will lose themselves and continue to wander
for life; in the second place, of those who, possessed of sufficient sense or
modesty to determine that there are others who excel them in the power of
discriminating between truth and error, and by whom they may be instructed,
ought rather to content themselves with the opinions of such than trust for
more correct to their own reason.

For my own part, I should
doubtless have belonged to the latter class, had I received instruction from
but one master, or had I never known the diversities of opinion that from time
immemorial have prevailed among men of the greatest learning. But I had become
aware, even so early as during my college life, that no opinion, however absurd
and incredible, can be imagined, which has not been maintained by some on of
the philosophers; and afterwards in the course of my travels I remarked that
all those whose opinions are decidedly repugnant to ours are not in that
account barbarians and savages, but on the contrary that many of these nations
make an equally good, if not better, use of their reason than we do. I took
into account also the very different character which a person brought up from
infancy in France or Germany exhibits, from that which, with the same mind
originally, this individual would have possessed had he lived always among the
Chinese or with savages, and the circumstance that in dress itself the fashion
which pleased us ten years ago, and which may again, perhaps, be received into
favor before ten years have gone, appears to us at this moment extravagant and
ridiculous. I was thus led to infer that the ground of our opinions is far more
custom and example than any certain knowledge. And, finally, although such be
the ground of our opinions, I remarked that a plurality of suffrages is no
guarantee of truth where it is at all of difficult discovery, as in such cases
it is much more likely that it will be found by one than by many. I could,
however, select from the crowd no one whose opinions seemed worthy of
preference, and thus I found myself constrained, as it were, to use my own
reason in the conduct of my life.

But like one walking alone and in
the dark, I resolved to proceed so slowly and with such circumspection, that if
I did not advance far, I would at least guard against falling. I did not even
choose to dismiss summarily any of the opinions that had crept into my belief
without having been introduced by reason, but first of all took sufficient time
carefully to satisfy myself of the general nature of the task I was setting
myself, and ascertain the true method by which to arrive at the knowledge of
whatever lay within the compass of my powers.

Among the branches of philosophy,
I had, at an earlier period, given some attention to logic, and among those of
the mathematics to geometrical analysis and algebra, -- three arts or sciences
which ought, as I conceived, to contribute something to my design. But, on
examination, I found that, as for logic, its syllogisms and the majority of its
other precepts are of avail- rather in the communication of what we already
know, or even as the art of Lully, in speaking without judgment of things of
which we are ignorant, than in the investigation of the unknown; and although
this science contains indeed a number of correct and very excellent precepts,
there are, nevertheless, so many others, and these either injurious or
superfluous, mingled with the former, that it is almost quite as difficult to
effect a severance of the true from the false as it is to extract a Diana or a
Minerva from a rough block of marble. Then as to the analysis of the ancients
and the algebra of the moderns, besides that they embrace only matters highly
abstract, and, to appearance, of no use, the former is so exclusively
restricted to the consideration of figures, that it can exercise the
understanding only on condition of greatly fatiguing the imagination; and, in
the latter, there is so complete a subjection to certain rules and formulas,
that there results an art full of confusion and obscurity calculated to embarrass,
instead of a science fitted to cultivate the mind. By these considerations I
was induced to seek some other method which would comprise the advantages of
the three and be exempt from their defects. And as a multitude of laws often
only hampers justice, so that a state is best governed when, with few laws,
these are rigidly administered; in like manner, instead of the great number of
precepts of which logic is composed, I believed that the four following would
prove perfectly sufficient for me, provided I took the firm and unwavering
resolution never in a single instance to fail in observing them.

The first was never to accept
anything for true which I did not clearly know to be such; that is to say,
carefully to avoid precipitancy and prejudice, and to comprise nothing more in
my judgement than what was presented to my mind so clearly and distinctly as to
exclude all ground of doubt.

The second, to divide each of the
difficulties under examination into as many parts as possible, and as might be
necessary for its adequate solution.

The third, to conduct my thoughts
in such order that, by commencing with objects the simplest and easiest to
know, I might ascend by little and little, and, as it were, step by step, to
the knowledge of the more complex; assigning in thought a certain order even to
those objects which in their own nature do not stand in a relation of
antecedence and sequence.

And the last, in every case to
make enumerations so complete, and reviews so general, that I might be assured
that nothing was omitted.

The long chains of simple and easy
reasonings by means of which geometers are accustomed to reach the conclusions
of their most difficult demonstrations, had led me to imagine that all things,
to the knowledge of which man is competent, are mutually connected in the same
way, and that there is nothing so far removed from us as to be beyond our
reach, or so hidden that we cannot discover it, provided only we abstain from
accepting the false for the true, and always preserve in our thoughts the order
necessary for the deduction of one truth from another. And I had little
difficulty in determining the objects with which it was necessary to commence,
for I was already persuaded that it must be with the simplest and easiest to
know, and, considering that of all those who have hitherto sought truth in the
sciences, the mathematicians alone have been able to find any demonstrations,
that is, any certain and evident reasons, I did not doubt but that such must
have been the rule of their investigations. I resolved to commence, therefore,
with the examination of the simplest objects, not anticipating, however, from
this any other advantage than that to be found in accustoming my mind to the
love and nourishment of truth, and to a distaste for all such reasonings as
were unsound. But I had no intention on that account of attempting to master
all the particular sciences commonly denominated mathematics: but observing
that, however different their objects, they all agree in considering only the
various relations or proportions subsisting among those objects, I thought it
best for my purpose to consider these proportions in the most general form
possible, without referring them to any objects in particular, except such as
would most facilitate the knowledge of them, and without by any means
restricting them to these, that afterwards I might thus be the better able to
apply them to every other class of objects to which they are legitimately
applicable. Perceiving further, that in order to understand these relations I
should sometimes have to consider them one by one and sometimes only to bear
them in mind, or embrace them in the aggregate, I thought that, in order the
better to consider them individually, I should view them as subsisting between
straight lines, than which I could find no objects more simple, or capable of
being more distinctly represented to my imagination and senses; and on the
other hand, that in order to retain them in the memory or embrace an aggregate
of many, I should express them by certain characters the briefest possible. In
this way I believed that I could borrow all that was best both in geometrical
analysis and in algebra, and correct all the defects of the one by help of the
other.

And, in point of fact, the
accurate observance of these few precepts gave me, I take the liberty of
saying, such ease in unraveling all the questions embraced in these two
sciences, that in the two or three months I devoted to their examination, not
only did I reach solutions of questions I had formerly deemed exceedingly
difficult but even as regards questions of the solution of which I continued
ignorant, I was enabled, as it appeared to me, to determine the means whereby,
and the extent to which a solution was possible; results attributable to the
circumstance that I commenced with the simplest and most general truths, and
that thus each truth discovered was a rule available in the discovery of
subsequent ones Nor in this perhaps shall I appear too vain, if it be
considered that, as the truth on any particular point is one whoever apprehends
the truth, knows all that on that point can be known. The child, for example,
who has been instructed in the elements of arithmetic, and has made a
particular addition, according to rule, may be assured that he has found, with
respect to the sum of the numbers before him, and that in this instance is
within the reach of human genius. Now, in conclusion, the method which teaches
adherence to the true order, and an exact enumeration of all the conditions of
the thing .sought includes all that gives certitude to the rules of arithmetic.

But the chief ground of my
satisfaction with thus method, was the assurance I had of thereby exercising my
reason in all matters, if not with absolute perfection, at least with the
greatest attainable by me: besides, I was conscious that by its use my mind was
becoming gradually habituated to clearer and more distinct conceptions of its
objects; and I hoped also, from not having restricted this method to any
particular matter, to apply it to the difficulties of the other sciences, with
not less success than to those of algebra. I should not, however, on this
account have ventured at once on the examination of all the difficulties of the
sciences which presented themselves to me, for this would have been contrary to
the order prescribed in the method, but observing that the knowledge of such is
dependent on principles borrowed from philosophy, in which I found nothing
certain, I thought it necessary first of all to endeavor to establish its principles.
.And because I observed, besides, that an inquiry of this kind was of all
others of the greatest moment, and one in which precipitancy and anticipation
in judgment were most to be dreaded, I thought that I ought not to approach it
till I had reached a more mature age (being at that time but twenty-three), and
had first of all employed much of my time in preparation for the work, as well
by eradicating from my mind all the erroneous opinions I had up to that moment
accepted, as by amassing variety of experience to afford materials for my
reasonings, and by continually exercising myself in my chosen method with a
view to increased skill in its application.

PART III

And finally, as it is not enough,
before commencing to rebuild the house in which we live, that it be pulled
down, and materials and builders provided, or that we engage in the work
ourselves, according to a plan which we have beforehand carefully drawn out,
but as it is likewise necessary that we be furnished with some other house in
which we may live commodiously during the operations, so that I might not
remain irresolute in my actions, while my reason compelled me to suspend my
judgement, and that I might not be prevented from living thenceforward in the
greatest possible felicity, I formed a provisory code of morals, composed of
three or four maxims, with which I am desirous to make you acquainted.

The first was to obey the laws and
customs of my country, adhering firmly to the faith in which, by the grace of
God, I had been educated from my childhood and regulating my conduct in every
other matter according to the most moderate opinions, and the farthest removed
from extremes, which should happen to be adopted in practice with general
consent of the most judicious of those among whom I might be living. For as I
had from that time begun to hold my own opinions for nought because I wished to
subject them all to examination, I was convinced that I could not do better
than follow in the meantime the opinions of the most judicious; and although there
are some perhaps among the Persians and Chinese as judicious as among
ourselves, expediency seemed to dictate that I should regulate my practice
conformably to the opinions of those with whom I should have to live; and it
appeared to me that, in order to ascertain the real opinions of such, I ought
rather to take cognizance of what they practised than of what they said, not
only because, in the corruption of our manners, there are few disposed to speak
exactly as they believe, but also because very many are not aware of what it is
that they really believe; for, as the act of mind by which a thing is believed
is different from that by which we know that we believe it, the one act is
often found without the other. Also, amid many opinions held in equal repute, I
chose always the most moderate, as much for the reason that these are always
the most convenient for practice, and probably the best (for all excess is
generally vicious), as that, in the event of my falling into error, I might be
at less distance from the truth than if, having chosen one of the extremes, it
should turn out to be the other which I ought to have adopted. And I placed in
the class of extremes especially all promises by which somewhat of our freedom
is abridged; not that I disapproved of the laws which, to provide against the
instability of men of feeble resolution, when what is sought to be accomplished
is some good, permit engagements by vows and contracts binding the parties to
persevere in it, or even, for the security of commerce, sanction similar
engagements where the purpose sought to be realized is indifferent: but because
I did not find anything on earth which was wholly superior to change, and
because, for myself in particular, I hoped gradually to perfect my judgments,
and not to suffer them to deteriorate, I would have deemed it a grave sin
against good sense, if, for the reason that I approved of something at a
particular time, I therefore bound myself to hold it for good at a subsequent
time, when perhaps it had ceased to be so, or I had ceased to esteem it such.

My second maxim was to be as firm
and resolute in my actions as I was able, and not to adhere less steadfastly to
the most doubtful opinions, when once adopted, than if they had been highly
certain; imitating in this the example of travelers who, when they have lost
their way in a forest, ought not to wander from side to side, far less remain
in one place, but proceed constantly towards the same side in as straight a
line as possible, without changing their direction for slight reasons, although
perhaps it might be chance alone which at first determined the selection; for
in this way, if they do not exactly reach the point they desire, they will come
at least in the end to some place that will probably be preferable to the
middle of a forest. In the same way, since in action it frequently happens that
no delay is permissible, it is very certain that, when it is not in our power
to determine what is true, we ought to act according to what is most probable;
and even although we should not remark a greater probability in one opinion
than in another, we ought notwithstanding to choose one or the other, and
afterwards consider it, in so far as it relates to practice, as no longer
dubious, but manifestly true and certain, since the reason by which our choice
has been determined is itself possessed of these qualities. This principle was
sufficient thenceforward to rid me of all those repentings and pangs of remorse
that usually disturb the consciences of such feeble and uncertain minds as,
destitute of any clear and determinate principle of choice, allow themselves
one day to adopt a course of action as the best, which they abandon the next,
as the opposite.

My third maxim was to endeavor
always to conquer myself rather than fortune, and change my desires rather than
the order of the world, and in general, accustom myself to the persuasion that,
except our own thoughts, there is nothing absolutely in our power; so that when
we have done our best in things external to us, all wherein we fail of success
is to be held, as regards us, absolutely impossible: and this single principle
seemed to me sufficient to prevent me from desiring for the future anything
which I could not obtain, and thus render me contented; for since our will naturally
seeks those objects alone which the understanding represents as in some way
possible of attainment, it is plain, that if we consider all external goods as
equally beyond our power, we shall no more regret the absence of such goods as
seem due to our birth, when deprived of them without any fault of ours, than
our not possessing the kingdoms of China or Mexico, and thus making, so to
speak, a virtue of necessity, we shall no more desire health in disease, or
freedom in imprisonment, than we now do bodies incorruptible as diamonds, or
the wings of birds to fly with. But I confess there is need of prolonged
discipline and frequently repeated meditation to accustom the mind to view all
objects in this light; and I believe that in this chiefly consisted the secret
of the power of such philosophers as in former times were enabled to rise
superior to the influence of fortune, and, amid suffering and poverty, enjoy a
happiness which their gods might have envied. For, occupied incessantly with
the consideration of the limits prescribed to their power by nature, they
became so entirely convinced that nothing was at their disposal except their
own thoughts, that this conviction was of itself sufficient to prevent their
entertaining any desire of other objects; and over their thoughts they acquired
a sway so absolute, that they had some ground on this account for esteeming
themselves more rich and more powerful, more free and more happy, than other
men who, whatever be the favors heaped on them by nature and fortune, if
destitute of this philosophy, can never command the realization of all their
desires.

In fine, to conclude this code of
morals, I thought of reviewing the different occupations of men in this life,
with the view of making choice of the best. And, without wishing to offer any
remarks on the employments of others, I may state that it was my conviction
that I could not do better than continue in that in which I was engaged, viz.,
in devoting my whole life to the culture of my reason, and in making the greatest
progress I was able in the knowledge of truth, on the principles of the method
which I had prescribed to myself. This method, from the time I had begun to
apply it, had been to me the source of satisfaction so intense as to lead me
to, believe that more perfect or more innocent could not be enjoyed in this
life; and as by its means I daily discovered truths that appeared to me of some
importance, and of which other men were generally ignorant, the gratification
thence arising so occupied my mind that I was wholly indifferent to every other
object. Besides, the three preceding maxims were founded singly on the design
of continuing the work of self- instruction. For since God has endowed each of
us with some light of reason by which to distinguish truth from error, I could
not have believed that I ought for a single moment to rest satisfied with the
opinions of another, unless I had resolved to exercise my own judgment in
examining these whenever I should be duly qualified for the task. Nor could I
have proceeded on such opinions without scruple, had I supposed that I should
thereby forfeit any advantage for attaining still more accurate, should such
exist. And, in fine, I could not have restrained my desires, nor remained
satisfied had I not followed a path in which I thought myself certain of
attaining all the knowledge to the acquisition of which I was competent, as
well as the largest amount of what is truly good which I could ever hope to
secure Inasmuch as we neither seek nor shun any object except in so far as our
understanding represents it as good or bad, all that is necessary to right
action is right judgment, and to the best action the most correct judgment,
that is, to the acquisition of all the virtues with all else that is truly
valuable and within our reach; and the assurance of such an acquisition cannot
fail to render us contented.

Having thus provided myself with
these maxims, and having placed them in reserve along with the truths of faith,
which have ever occupied the first place in my belief, I came to the conclusion
that I might with freedom set about ridding myself of what remained of my
opinions. And, inasmuch as I hoped to be better able successfully to accomplish
this work by holding intercourse with mankind, than by remaining longer shut up
in the retirement where these thoughts had occurred to me, I betook me again to
traveling before the winter was well ended. And, during the nine subsequent
years, I did nothing but roam from one place to another, desirous of being a
spectator rather than an actor in the plays exhibited on the theater of the
world; and, as I made it my business in each matter to reflect particularly
upon what might fairly be doubted and prove a source of error, I gradually
rooted out from my mind all the errors which had hitherto crept into it. Not
that in this I imitated the sceptics who doubt only that they may doubt, and
seek nothing beyond uncertainty itself; for, on the contrary, my design was
singly to find ground of assurance, and cast aside the loose earth and sand,
that I might reach the rock or the clay. In this, as appears to me, I was
successful enough; for, since I endeavored to discover the falsehood or
incertitude of the propositions I examined, not by feeble conjectures, but by
clear and certain reasonings, I met with nothing so doubtful as not to yield
some conclusion of adequate certainty, although this were merely the inference,
that the matter in question contained nothing certain. And, just as in pulling
down an old house, we usually reserve the ruins to contribute towards the
erection, so, in destroying such of my opinions as I judged to be Ill-founded,
I made a variety of observations and acquired an amount of experience of which
I availed myself in the establishment of more certain. And further, I continued
to exercise myself in the method I had prescribed; for, besides taking care in
general to conduct all my thoughts according to its rules, I reserved some
hours from time to time which I expressly devoted to the employment of the
method in the solution of mathematical difficulties, or even in the solution
likewise of some questions belonging to other sciences, but which, by my having
detached them from such principles of these sciences as were of inadequate
certainty, were rendered almost mathematical: the truth of this will be
manifest from the numerous examples contained in this volume. And thus, without
in appearance living otherwise than those who, with no other occupation than
that of spending their lives agreeably and innocently, study to sever pleasure
from vice, and who, that they may enjoy their leisure without ennui, have
recourse to such pursuits as are honorable, I was nevertheless prosecuting my
design, and making greater progress in the knowledge of truth, than I might,
perhaps, have made had I been engaged in the perusal of books merely, or in
holding converse with men of letters.

These nine years passed away,
however, before I had come to any determinate judgment respecting the
difficulties which form matter of dispute among the learned, or had commenced
to seek the principles of any philosophy more certain than the vulgar. And the
examples of many men of the highest genius, who had, in former times, engaged
in this inquiry, but, as appeared to me, without success, led me to imagine it to
be a work of so much difficulty, that I would not perhaps have ventured on it
so soon had I not heard it currently rumored that I had already completed the
inquiry. I know not what were the grounds of this opinion; and, if my
conversation contributed in any measure to its rise, this must have happened
rather from my having confessed my Ignorance with greater freedom than those
are accustomed to do who have studied a little, and expounded perhaps, the
reasons that led me to doubt of many of those things that by others are
esteemed certain, than from my having boasted of any system of philosophy. But,
as I am of a disposition that makes me unwilling to be esteemed different from
what I really am, I thought it necessary to endeavor by all means to render myself
worthy of the reputation accorded to me; and it is now exactly eight years
since this desire constrained me to remove from all those places where
interruption from any of my acquaintances was possible, and betake myself to
this country, in which the long duration of the war has led to the
establishment of such discipline, that the armies maintained seem to be of use
only in enabling the inhabitants to enjoy more securely the blessings of peace
and where, in the midst of a great crowd actively engaged in business, and more
careful of their own affairs than curious about those of others, I have been
enabled to live without being deprived of any of the conveniences to be had in
the most populous cities, and yet as solitary and as retired as in the midst of
the most remote deserts.

PART IV

I am in doubt as to the propriety
of making my first meditations in the place above mentioned matter of
discourse; for these are so metaphysical, and so uncommon, as not, perhaps, to
be acceptable to every one. And yet, that it may be determined whether the
foundations that I have laid are sufficiently secure, I find myself in a
measure constrained to advert to them. I had long before remarked that, in
relation to practice, it is sometimes necessary to adopt, as if above doubt,
opinions which we discern to be highly uncertain, as has been already said; but
as I then desired to give my attention solely to the search after truth, I
thought that a procedure exactly the opposite was called for, and that I ought
to reject as absolutely false all opinions in regard to which I could suppose
the least ground for doubt, in order to ascertain whether after that there
remained aught in my belief that was wholly indubitable. Accordingly, seeing
that our senses sometimes deceive us, I was willing to suppose that there
existed nothing really such as they presented to us; and because some men err
in reasoning, and fall into paralogisms, even on the simplest matters of
geometry, I, convinced that I was as open to error as any other, rejected as
false all the reasonings I had hitherto taken for demonstrations; and finally,
when I considered that the very same thoughts (presentations) which we
experience when awake may also be experienced when we are asleep, while there
is at that time not one of them true, I supposed that all the objects
(presentations) that had ever entered into my mind when awake, had in them no
more truth than the illusions of my dreams. But immediately upon this I
observed that, whilst I thus wished to think that all was false, it was
absolutely necessary that I, who thus thought, should be somewhat; and as I
observed that this truth, I think, therefore I am (COGITO ERGO SUM), was so
certain and of such evidence that no ground of doubt, however extravagant,
could be alleged by the sceptics capable of shaking it, I concluded that I
might, without scruple, accept it as the first principle of the philosophy of
which I was in search

In the next place, I attentively
examined what I was and as I observed that I could suppose that I had no body,
and that there was no world nor any place in which I might be; but that I could
not therefore suppose that I was not; and that, on the contrary, from the very
circumstance that I thought to doubt of the truth of other things, it most
clearly and certainly followed that I was; while, on the other hand, if I had
only ceased to think, although all the other objects which I had ever imagined
had been in reality existent, I would have had no reason to believe that I
existed; I thence concluded that I was a substance whose whole essence or
nature consists only in thinking, and which, that it may exist, has need of no
place, nor is dependent on any material thing; so that " I," that is
to say, the mind by which I am what I am, is wholly distinct from the body, and
is even more easily known than the latter, and is such, that although the
latter were not, it would still continue to be all that it is.

After this I inquired in general
into what is essential I to the truth and certainty of a proposition; for since
I had discovered one which I knew to be true, I thought that I must likewise be
able to discover the ground of this certitude. And as I observed that in the
words I think, therefore I am, there is nothing at all which gives me assurance
of their truth beyond this, that I see very clearly that in order to think it
is necessary to exist, I concluded that I might take, as a general rule, the
principle, that all the things which we very clearly and distinctly conceive
are true, only observing, however, that there is some difficulty in rightly
determining the objects which we distinctly conceive.

In the next place, from reflecting
on the circumstance that I doubted, and that consequently my being was not
wholly perfect (for I clearly saw that it was a greater perfection to know than
to doubt), I was led to inquire whence I had learned to think of something more
perfect than myself; and I clearly recognized that I must hold this notion from
some nature which in reality was more perfect. As for the thoughts of many
other objects external to me, as of the sky, the earth, light, heat, and a
thousand more, I was less at a loss to know whence these came; for since I
remarked in them nothing which seemed to render them superior to myself, I
could believe that, if these were true, they were dependencies on my own
nature, in so far as it possessed a certain perfection, and, if they were
false, that I held them from nothing, that is to say, that they were in me
because of a certain imperfection of my nature. But this could not be the case
with-the idea of a nature more perfect than myself; for to receive it from
nothing was a thing manifestly impossible; and, because it is not less
repugnant that the more perfect should be an effect of, and dependence on the
less perfect, than that something should proceed from nothing, it was equally
impossible that I could hold it from myself: accordingly, it but remained that
it had been placed in me by a nature which was in reality more perfect than
mine, and which even possessed within itself all the perfections of which I
could form any idea; that is to say, in a single word, which was God. And to
this I added that, since I knew some perfections which I did not possess, I was
not the only being in existence (I will here, with your permission, freely use
the terms of the schools); but, on the contrary, that there was of necessity
some other more perfect Being upon whom I was dependent, and from whom I had
received all that I possessed; for if I had existed alone, and independently of
every other being, so as to have had from myself all the perfection, however
little, which I actually possessed, I should have been able, for the same
reason, to have had from myself the whole remainder of perfection, of the want
of which I was conscious, and thus could of myself have become infinite,
eternal, immutable, omniscient, all-powerful, and, in fine, have possessed all
the perfections which I could recognize in God. For in order to know the nature
of God (whose existence has been established by the preceding reasonings), as
far as my own nature permitted, I had only to consider in reference to all the
properties of which I found in my mind some idea, whether their possession was
a mark of perfection; and I was assured that no one which indicated any
imperfection was in him, and that none of the rest was awanting. Thus I
perceived that doubt, inconstancy, sadness, and such like, could not be found
in God, since I myself would have been happy to be free from them. Besides, I
had ideas of many sensible and corporeal things; for although I might suppose
that I was dreaming, and that all which I saw or imagined was false, I could
not, nevertheless, deny that the ideas were in reality in my thoughts. But,
because I had already very clearly recognized in myself that the intelligent
nature is distinct from the corporeal, and as I observed that all composition
is an evidence of dependency, and that a state of dependency is manifestly a
state of imperfection, I therefore determined that it could not be a perfection
in God to be compounded of these two natures and that consequently he was not
so compounded; but that if there were any bodies in the world, or even any
intelligences, or other natures that were not wholly perfect, their existence
depended on his power in such a way that they could not subsist without him for
a single moment.

I was disposed straightway to
search for other truths and when I had represented to myself the object of the
geometers, which I conceived to be a continuous body or a space indefinitely
extended in length, breadth, and height or depth, divisible into divers parts
which admit of different figures and sizes, and of being moved or transposed in
all manner of ways (for all this the geometers suppose to be in the object they
contemplate), I went over some of their simplest demonstrations. And, in the
first place, I observed, that the great certitude which by common consent is
accorded to these demonstrations, is founded solely upon this, that they are
clearly conceived in accordance with the rules I have already laid down In the
next place, I perceived that there was nothing at all in these demonstrations
which could assure me of the existence of their object: thus, for example,
supposing a triangle to be given, I distinctly perceived that its three angles
were necessarily equal to two right angles, but I did not on that account
perceive anything which could assure me that any triangle existed: while, on
the contrary, recurring to the examination of the idea of a Perfect Being, I
found that the existence of the Being was comprised in the idea in the same way
that the equality of its three angles to two right angles is comprised in the
idea of a triangle, or as in the idea of a sphere, the equidistance of all
points on its surface from the center, or even still more clearly; and that
consequently it is at least as certain that God, who is this Perfect Being, is,
or exists, as any demonstration of geometry can be.

But the reason which leads many to
persuade them selves that there is a difficulty in knowing this truth, and even
also in knowing what their mind really is, is that they never raise their
thoughts above sensible objects, and are so accustomed to consider nothing
except by way of imagination, which is a mode of thinking limited to material
objects, that all that is not imaginable seems to them not intelligible. The
truth of this is sufficiently manifest from the single circumstance, that the
philosophers of the schools accept as a maxim that there is nothing in the
understanding which was not previously in the senses, in which however it is
certain that the ideas of God and of the soul have never been; and it appears
to me that they who make use of their imagination to comprehend these ideas do
exactly the some thing as if, in order to hear sounds or smell odors, they
strove to avail themselves of their eyes; unless indeed that there is this
difference, that the sense of sight does not afford us an inferior assurance to
those of smell or hearing; in place of which, neither our imagination nor our
senses can give us assurance of anything unless our understanding intervene.

Finally, if there be still persons
who are not sufficiently persuaded of the existence of God and of the soul, by
the reasons I have adduced, I am desirous that they should know that all the
other propositions, of the truth of which they deem themselves perhaps more
assured, as that we have a body, and that there exist stars and an earth, and
such like, are less certain; for, although we have a moral assurance of these things,
which is so strong that there is an appearance of extravagance in doubting of
their existence, yet at the same time no one, unless his intellect is impaired,
can deny, when the question relates to a metaphysical certitude, that there is
sufficient reason to exclude entire assurance, in the observation that when
asleep we can in the same way imagine ourselves possessed of another body and
that we see other stars and another earth, when there is nothing of the kind.
For how do we know that the thoughts which occur in dreaming are false rather
than those other which we experience when awake, since the former are often not
less vivid and distinct than the latter? And though men of the highest genius
study this question as long as they please, I do not believe that they will be
able to give any reason which can be sufficient to remove this doubt, unless
they presuppose the existence of God. For, in the first place even the
principle which I have already taken as a rule, viz., that all the things which
we clearly and distinctly conceive are true, is certain only because God is or
exists and because he is a Perfect Being, and because all that we possess is
derived from him: whence it follows that our ideas or notions, which to the
extent of their clearness and distinctness are real, and proceed from God, must
to that extent be true. Accordingly, whereas we not infrequently have ideas or
notions in which some falsity is contained, this can only be the case with such
as are to some extent confused and obscure, and in this proceed from nothing
(participate of negation), that is, exist in us thus confused because we are
not wholly perfect. And it is evident that it is not less repugnant that
falsity or imperfection, in so far as it is imperfection, should proceed from
God, than that truth or perfection should proceed from nothing. But if we did
not know that all which we possess of real and true proceeds from a Perfect and
Infinite Being, however clear and distinct our ideas might be, we should have
no ground on that account for the assurance that they possessed the perfection
of being true.

But after the knowledge of God and
of the soul has rendered us certain of this rule, we can easily understand that
the truth of the thoughts we experience when awake, ought not in the slightest
degree to be called in question on account of the illusions of our dreams. For
if it happened that an individual, even when asleep, had some very distinct
idea, as, for example, if a geometer should discover some new demonstration,
the circumstance of his being asleep would not militate against its truth; and
as for the most ordinary error of our dreams, which consists in their
representing to us various objects in the same way as our external senses, this
is not prejudicial, since it leads us very properly to suspect the truth of the
ideas of sense; for we are not infrequently deceived in the same manner when
awake; as when persons in the jaundice see all objects yellow, or when the
stars or bodies at a great distance appear to us much smaller than they are.
For, in fine, whether awake or asleep, we ought never to allow ourselves to be
persuaded of the truth of anything unless on the evidence of our reason. And it
must be noted that I say of our reason, and not of our imagination or of our senses:
thus, for example, although we very clearly see the sun, we ought not therefore
to determine that it is only of the size which our sense of sight presents; and
we may very distinctly imagine the head of a lion joined to the body of a goat,
without being therefore shut up to the conclusion that a chimaera exists; for
it is not a dictate of reason that what we thus see or imagine is in reality
existent; but it plainly tells us that all our ideas or notions contain in them
some truth; for otherwise it could not be that God, who is wholly perfect and
veracious, should have placed them in us. And because our reasonings are never
so clear or so complete during sleep as when we are awake, although sometimes
the acts of our imagination are then as lively and distinct, if not more so
than in our waking moments, reason further dictates that, since all our
thoughts cannot be true because of our partial imperfection, those possessing
truth must infallibly be found in the experience of our waking moments rather
than in that of our dreams.

PART V

I would here willingly have
proceeded to exhibit the whole chain of truths which I deduced from these
primary but as with a view to this it would have been necessary now to treat of
many questions in dispute among the earned, with whom I do not wish to be
embroiled, I believe that it will be better for me to refrain from this
exposition, and only mention in general what these truths are, that the more
judicious may be able to determine whether a more special account of them would
conduce to the public advantage. I have ever remained firm in my original
resolution to suppose no other principle than that of which I have recently
availed myself in demonstrating the existence of God and of the soul, and to
accept as true nothing that did not appear to me more clear and certain than
the demonstrations of the geometers had formerly appeared; and yet I venture to
state that not only have I found means to satisfy myself in a short time on all
the principal difficulties which are usually treated of in philosophy, but I
have also observed certain laws established in nature by God in such a manner,
and of which he has impressed on our minds such notions, that after we have
reflected sufficiently upon these, we cannot doubt that they are accurately
observed in all that exists or takes place in the world and farther, by
considering the concatenation of these laws, it appears to me that I have
discovered many truths more useful and more important than all I had before
learned, or even had expected to learn.

But because I have essayed to
expound the chief of these discoveries in a treatise which certain
considerations prevent me from publishing, I cannot make the results known more
conveniently than by here giving a summary of the contents of this treatise. It
was my design to comprise in it all that, before I set myself to write it, I
thought I knew of the nature of material objects. But like the painters who,
finding themselves unable to represent equally well on a plain surface all the
different faces of a solid body, select one of the chief, on which alone they
make the light fall, and throwing the rest into the shade, allow them to appear
only in so far as they can be seen while looking at the principal one; so,
fearing lest I should not be able to compense in my discourse all that was in
my mind, I resolved to expound singly, though at considerable length, my
opinions regarding light; then to take the opportunity of adding something on
the sun and the fixed stars, since light almost wholly proceeds from them; on
the heavens since they transmit it; on the planets, comets, and earth, since
they reflect it; and particularly on all the bodies that are upon the earth,
since they are either colored, or transparent, or luminous; and finally on man,
since he is the spectator of these objects. Further, to enable me to cast this
variety of subjects somewhat into the shade, and to express my judgment
regarding them with greater freedom, without being necessitated to adopt or
refute the opinions of the learned, I resolved to leave all the people here to
their disputes, and to speak only of what would happen in a new world, if God
were now to create somewhere in the imaginary spaces matter sufficient to
compose one, and were to agitate variously and confusedly the different parts
of this matter, so that there resulted a chaos as disordered as the poets ever
feigned, and after that did nothing more than lend his ordinary concurrence to
nature, and allow her to act in accordance with the laws which he had established.
On this supposition, I, in the first place, described this matter, and essayed
to represent it in such a manner that to my mind there can be nothing clearer
and more intelligible, except what has been recently said regarding God and the
soul; for I even expressly supposed that it possessed none of those forms or
qualities which are so debated in the schools, nor in general anything the
knowledge of which is not so natural to our minds that no one can so much as
imagine himself ignorant of it. Besides, I have pointed out what are the laws
of nature; and, with no other principle upon which to found my reasonings
except the infinite perfection of God, I endeavored to demonstrate all those
about which there could be any room for doubt, and to prove that they are such,
that even if God had created more worlds, there could have been none in which
these laws were not observed. Thereafter, I showed how the greatest part of the
matter of this chaos must, in accordance with these laws, dispose and arrange
itself in such a way as to present the appearance of heavens; how in the
meantime some of its parts must compose an earth and some planets and comets,
and others a sun and fixed stars. And, making a digression at this stage on the
subject of light, I expounded at considerable length what the nature of that
light must be which is found in the sun and the stars, and how thence in an
instant of time it traverses the immense spaces of the heavens, and how from
the planets and comets it is reflected towards the earth. To this I likewise
added much respecting the substance, the situation, the motions, and all the
different qualities of these heavens and stars; so that I thought I had said
enough respecting them to show that there is nothing observable in the heavens
or stars of our system that must not, or at least may not appear precisely
alike in those of the system which I described. I came next to speak of the
earth in particular, and to show how, even though I had expressly supposed that
God had given no weight to the matter of which it is composed, this should not
prevent all its parts from tending exactly to its center; how with water and
air on its surface, the disposition of the heavens and heavenly bodies, more
especially of the moon, must cause a flow and ebb, like in all its
circumstances to that observed in our seas, as also a certain current both of
water and air from east to west, such as is likewise observed between the
tropics; how the mountains, seas, fountains, and rivers might naturally be
formed in it, and the metals produced in the mines, and the plants grow in the
fields and in general, how all the bodies which are commonly denominated mixed
or composite might be generated and, among other things in the discoveries
alluded to inasmuch as besides the stars, I knew nothing except fire which
produces light, I spared no pains to set forth all that pertains to its nature,
-- the manner of its production and support, and to explain how heat is
sometimes found without light, and light without heat; to show how it can
induce various colors upon different bodies and other diverse qualities; how it
reduces some to a liquid state and hardens others; how it can consume almost
all bodies, or convert them into ashes and smoke; and finally, how from these
ashes, by the mere intensity of its action, it forms glass: for as this
transmutation of ashes into glass appeared to me as wonderful as any other in
nature, I took a special pleasure in describing it. I was not, however,
disposed, from these circumstances, to conclude that this world had been
created in the manner I described; for it is much more likely that God made it
at the first such as it was to be. But this is certain, and an opinion commonly
received among theologians, that the action by which he now sustains it is the
same with that by which he originally created it; so that even although he had
from the beginning given it no other form than that of chaos, provided only he
had established certain laws of nature, and had lent it his concurrence to
enable it to act as it is wont to do, it may be believed, without discredit to
the miracle of creation, that, in this way alone, things purely material might,
in course of time, have become such as we observe them at present; and their
nature is much more easily conceived when they are beheld coming in this manner
gradually into existence, than when they are only considered as produced at
once in a finished and perfect state.

From the description of inanimate
bodies and plants, I passed to animals, and particularly to man. But since I
had not as yet sufficient knowledge to enable me to treat of these in the same
manner as of the rest, that is to say, by deducing effects from their causes,
and by showing from what elements and in what manner nature must produce them,
I remained satisfied with the supposition that God formed the body of man
wholly like to one of ours, as well in the external shape of the members as in
the internal conformation of the organs, of the same matter with that I had
described, and at first placed in it no rational soul, nor any other principle,
in room of the vegetative or sensitive soul, beyond kindling in the heart one
of those fires without light, such as I had already described, and which I
thought was not different from the heat in hay that has been heaped together
before it is dry, or that which causes fermentation in new wines before they
are run clear of the fruit. For, when I examined the kind of functions which
might, as consequences of this supposition, exist in this body, I found precisely
all those which may exist in us independently of all power of thinking, and
consequently without being in any measure owing to the soul; in other words, to
that part of us which is distinct from the body, and of which it has been said
above that the nature distinctively consists in thinking, functions in which
the animals void of reason may be said wholly to resemble us; but among which I
could not discover any of those that, as dependent on thought alone, belong to
us as men, while, on the other hand, I did afterwards discover these as soon as
I supposed God to have created a rational soul, and to have annexed it to this
body in a particular manner which I described.

But, in order to show how I there
handled this matter, I mean here to give the explication of the motion of the
heart and arteries, which, as the first and most general motion observed in
animals, will afford the means of readily determining what should be thought of
all the rest. And that there may be less difficulty in understanding what I am
about to say on this subject, I advise those who are not versed in anatomy,
before they commence the perusal of these observations, to take the trouble of
getting dissected in their presence the heart of some large animal possessed of
lungs (for this is throughout sufficiently like the human), and to have shown
to them its two ventricles or cavities: in the first place, that in the right
side, with which correspond two very ample tubes, viz., the hollow vein (vena
cava), which is the principal receptacle of the blood, and the trunk of the
tree, as it were, of which all the other veins in the body are branches; and
the arterial vein (vena arteriosa), inappropriately so denominated, since it is
in truth only an artery, which, taking its rise in the heart, is divided, after
passing out from it, into many branches which presently disperse themselves all
over the lungs; in the second place, the cavity in the left side, with which
correspond in the same manner two canals in size equal to or larger than the
preceding, viz., the venous artery (arteria venosa), likewise inappropriately
thus designated, because it is simply a vein which comes from the lungs, where
it is divided into many branches, interlaced with those of the arterial vein,
and those of the tube called the windpipe, through which the air we breathe
enters; and the great artery which, issuing from the heart, sends its branches
all over the body. I should wish also that such persons were carefully shown
the eleven pellicles which, like so many small valves, open and shut the four
orifices that are in these two cavities, viz., three at the entrance of the
hollow veins where they are disposed in such a manner as by no means to prevent
the blood which it contains from flowing into the right ventricle of the heart,
and yet exactly to prevent its flowing out; three at the entrance to the
arterial vein, which, arranged in a manner exactly the opposite of the former,
readily permit the blood contained in this cavity to pass into the lungs, but
hinder that contained in the lungs from returning to this cavity; and, in like
manner, two others at the mouth of the venous artery, which allow the blood
from the lungs to flow into the left cavity of the heart, but preclude its
return; and three at the mouth of the great artery, which suffer the blood to
flow from the heart, but prevent its reflux. Nor do we need to seek any other
reason for the number of these pellicles beyond this that the orifice of the
venous artery being of an oval shape from the nature of its situation, can be
adequately closed with two, whereas the others being round are more
conveniently closed with three. Besides, I wish such persons to observe that
the grand artery and the arterial vein are of much harder and firmer texture
than the venous artery and the hollow vein; and that the two last expand before
entering the heart, and there form, as it were, two pouches denominated the
auricles of the heart, which are composed of a substance similar to that of the
heart itself; and that there is always more warmth in the heart than in any
other part of the body- and finally, that this heat is capable of causing any
drop of blood that passes into the cavities rapidly to expand and dilate, just
as all liquors do when allowed to fall drop by drop into a highly heated
vessel.

For, after these things, it is not
necessary for me to say anything more with a view to explain the motion of the
heart, except that when its cavities are not full of blood, into these the
blood of necessity flows, - - from the hollow vein into the right, and from the
venous artery into the left; because these two vessels are always full of
blood, and their orifices, which are turned towards the heart, cannot then be
closed. But as soon as two drops of blood have thus passed, one into each of the
cavities, these drops which cannot but be very large, because the orifices
through which they pass are wide, and the vessels from which they come full of
blood, are immediately rarefied, and dilated by the heat they meet with. In
this way they cause the whole heart to expand, and at the same time press home
and shut the five small valves that are at the entrances of the two vessels
from which they flow, and thus prevent any more blood from coming down into the
heart, and becoming more and more rarefied, they push open the six small valves
that are in the orifices of the other two vessels, through which they pass out,
causing in this way all the branches of the arterial vein and of the grand
artery to expand almost simultaneously with the heart which immediately
thereafter begins to contract, as do also the arteries, because the blood that
has entered them has cooled, and the six small valves close, and the five of
the hollow vein and of the venous artery open anew and allow a passage to other
two drops of blood, which cause the heart and the arteries again to expand as
before. And, because the blood which thus enters into the heart passes through
these two pouches called auricles, it thence happens that their motion is the
contrary of that of the heart, and that when it expands they contract. But lest
those who are ignorant of the force of mathematical demonstrations and who are
not accustomed to distinguish true reasons from mere verisimilitudes, should
venture. without examination, to deny what has been said, I wish it to be
considered that the motion which I have now explained follows as necessarily
from the very arrangement of the parts, which may be observed in the heart by
the eye alone, and from the heat which may be felt with the fingers, and from the
nature of the blood as learned from experience, as does the motion of a clock
from the power, the situation, and shape of its counterweights and wheels.

But if it be asked how it happens
that the blood in the veins, flowing in this way continually into the heart, is
not exhausted, and why the arteries do not become too full, since all the blood
which passes through the heart flows into them, I need only mention in reply
what has been written by a physician 1 of England, who has the honor of having
broken the ice on this subject, and of having been the first to teach that
there are many small passages at the extremities of the arteries, through which
the blood received by them from the heart passes into the small branches of the
veins, whence it again returns to the heart; so that its course amounts
precisely to a perpetual circulation. Of this we have abundant proof in the
ordinary experience of surgeons, who, by binding the arm with a tie of moderate
straitness above the part where they open the vein, cause the blood to flow
more copiously than it would have done without any ligature; whereas quite the
contrary would happen were they to bind it below; that is, between the hand and
the opening, or were to make the ligature above the opening very tight. For it
is manifest that the tie, moderately straightened, while adequate to hinder the
blood already in the arm from returning towards the heart by the veins, cannot
on that account prevent new blood from coming forward through the arteries,
because these are situated below the veins, and their coverings, from their
greater consistency, are more difficult to compress; and also that the blood
which comes from the heart tends to pass through them to the hand with greater
force than it does to return from the hand to the heart through the veins. And
since the latter current escapes from the arm by the opening made in one of the
veins, there must of necessity be certain passages below the ligature, that is,
towards the extremities of the arm through which it can come thither from the
arteries. This physician likewise abundantly establishes what he has advanced
respecting the motion of the blood, from the existence of certain pellicles, so
disposed in various places along the course of the veins, in the manner of small
valves, as not to permit the blood to pass from the middle of the body towards
the extremities, but only to return from the extremities to the heart; and
farther, from experience which shows that all the blood which is in the body
may flow out of it in a very short time through a single artery that has been
cut, even although this had been closely tied in the immediate neighborhood of
the heart and cut between the heart and the ligature, so as to prevent the
supposition that the blood flowing out of it could come from any other quarter
than the heart.

But there are many other
circumstances which evince that what I have alleged is the true cause of the
motion of the blood: thus, in the first place, the difference that is observed
between the blood which flows from the veins, and that from the arteries, can
only arise from this, that being rarefied, and, as it were, distilled by
passing through the heart, it is thinner, and more vivid, and warmer
immediately after leaving the heart, in other words, when in the arteries, than
it was a short time before passing into either, in other words, when it was in
the veins; and if attention be given, it will be found that this difference is
very marked only in the neighborhood of the heart; and is not so evident in
parts more remote from it. In the next place, the consistency of the coats of
which the arterial vein and the great artery are composed, sufficiently shows
that the blood is impelled against them with more force than against the veins.
And why should the left cavity of the heart and the great artery be wider and
larger than the right cavity and the arterial vein, were it not that the blood
of the venous artery, having only been in the lungs after it has passed through
the heart, is thinner, and rarefies more readily, and in a higher degree, than
the blood which proceeds immediately from the hollow vein? And what can
physicians conjecture from feeling the pulse unless they know that according as
the blood changes its nature it can be rarefied by the warmth of the heart, in
a higher or lower degree, and more or less quickly than before? And if it be
inquired how this heat is communicated to the other members, must it not be
admitted that this is effected by means of the blood, which, passing through
the heart, is there heated anew, and thence diffused over all the body? Whence
it happens, that if the blood be withdrawn from any part, the heat is likewise
withdrawn by the same means; and although the heart were as-hot as glowing
iron, it would not be capable of warming the feet and hands as at present,
unless it continually sent thither new blood. We likewise perceive from this,
that the true use of respiration is to bring sufficient fresh air into the
lungs, to cause the blood which flows into them from the right ventricle of the
heart, where it has been rarefied and, as it were, changed into vapors, to
become thick, and to convert it anew into blood, before it flows into the left
cavity, without which process it would be unfit for the nourishment of the fire
that is there. This receives confirmation from the circumstance, that it is
observed of animals destitute of lungs that they have also but one cavity in
the heart, and that in children who cannot use them while in the womb, there is
a hole through which the blood flows from the hollow vein into the left cavity
of the heart, and a tube through which it passes from the arterial vein into
the grand artery without passing through the lung. In the next place, how could
digestion be carried on in the stomach unless the heart communicated heat to it
through the arteries, and along with this certain of the more fluid parts of
the blood, which assist in the dissolution of the food that has been taken in?
Is not also the operation which converts the juice of food into blood easily
comprehended, when it is considered that it is distilled by passing and
repassing through the heart perhaps more than one or two hundred times in a
day? And what more need be adduced to explain nutrition, and the production of
the different humors of the body, beyond saying, that the force with which the
blood, in being rarefied, passes from the heart towards the extremities of the
arteries, causes certain of its parts to remain in the members at which they
arrive, and there occupy the place of some others expelled by them; and that
according to the situation, shape, or smallness of the pores with which they
meet, some rather than others flow into certain parts, in the same way that
some sieves are observed to act, which, by being variously perforated, serve to
separate different species of grain? And, in the last place, what above all is
here worthy of observation, is the generation of the animal spirits, which are
like a very subtle wind, or rather a very pure and vivid flame which,
continually ascending in great abundance from the heart to the brain, thence
penetrates through the nerves into the muscles, and gives motion to all the
members; so that to account for other parts of the blood which, as most
agitated and penetrating, are the fittest to compose these spirits, proceeding
towards the brain, it is not necessary to suppose any other cause, than simply,
that the arteries which carry them thither proceed from the heart in the most
direct lines, and that, according to the rules of mechanics which are the same
with those of nature, when many objects tend at once to the same point where
there is not sufficient room for all (as is the case with the parts of the
blood which flow forth from the left cavity of the heart and tend towards the
brain), the weaker and less agitated parts must necessarily be driven aside
from that point by the stronger which alone in this way reach it I had
expounded all these matters with sufficient minuteness in the treatise which I
formerly thought of publishing. And after these, I had shown what must be the
fabric of the nerves and muscles of the human body to give the animal spirits
contained in it the power to move the members, as when we see heads shortly
after they have been struck off still move and bite the earth, although no
longer animated; what changes must take place in the brain to produce waking,
sleep, and dreams; how light, sounds, odors, tastes, heat, and all the other
qualities of external objects impress it with different ideas by means of the
senses; how hunger, thirst, and the other internal affections can likewise
impress upon it divers ideas; what must be understood by the common sense
(sensus communis) in which these ideas are received, by the memory which
retains them, by the fantasy which can change them in various ways, and out of
them compose new ideas, and which, by the same means, distributing the animal
spirits through the muscles, can cause the members of such a body to move in as
many different ways, and in a manner as suited, whether to the objects that are
presented to its senses or to its internal affections, as can take place in our
own case apart from the guidance of the will. Nor will this appear at all
strange to those who are acquainted with the variety of movements performed by
the different automata, or moving machines fabricated by human industry, and
that with help of but few pieces compared with the great multitude of bones,
muscles, nerves, arteries, veins, and other parts that are found in the body of
each animal. Such persons will look upon this body as a machine made by the
hands of God, which is incomparably better arranged, and adequate to movements
more admirable than is any machine of human invention. And here I specially
stayed to show that, were there such machines exactly resembling organs and
outward form an ape or any other irrational animal, we could have no means of
knowing that they were in any respect of a different nature from these animals;
but if there were machines bearing the image of our bodies, and capable of
imitating our actions as far as it is morally possible, there would still
remain two most certain tests whereby to know that they were not therefore
really men. Of these the first is that they could never use words or other
signs arranged in such a manner as is competent to us in order to declare our
thoughts to others: for we may easily conceive a machine to be so constructed
that it emits vocables, and even that it emits some correspondent to the action
upon it of external objects which cause a change in its organs; for example, if
touched in a particular place it may demand what we wish to say to it; if in
another it may cry out that it is hurt, and such like; but not that it should
arrange them variously so as appositely to reply to what is said in its
presence, as men of the lowest grade of intellect can do. The second test is,
that although such machines might execute many things with equal or perhaps
greater perfection than any of us, they would, without doubt, fail in certain
others from which it could be discovered that they did not act from knowledge,
but solely from the disposition of their organs: for while reason is an
universal instrument that is alike available on every occasion, these organs,
on the contrary, need a particular arrangement for each particular action;
whence it must be morally impossible that there should exist in any machine a
diversity of organs sufficient to enable it to act in all the occurrences of
life, in the way in which our reason enables us to act. Again, by means of
these two tests we may likewise know the difference between men and brutes. For
it is highly deserving of remark, that there are no men so dull and stupid, not
even idiots, as to be incapable of joining together different words, and
thereby constructing a declaration by which to make their thoughts understood;
and that on the other hand, there is no other animal, however perfect or
happily circumstanced, which can do the like. Nor does this inability arise
from want of organs: for we observe that magpies and parrots can utter words
like ourselves, and are yet unable to speak as we do, that is, so as to show
that they understand what they say; in place of which men born deaf and dumb,
and thus not less, but rather more than the brutes, destitute of the organs
which others use in speaking, are in the habit of spontaneously inventing
certain signs by which they discover their thoughts to those who, being usually
in their company, have leisure to learn their language. And this proves not
only that the brutes have less reason than man, but that they have none at all:
for we see that very little is required to enable a person to speak; and since
a certain inequality of capacity is observable among animals of the same
species, as well as among men, and since some are more capable of being
instructed than others, it is incredible that the most perfect ape or parrot of
its species, should not in this be equal to the most stupid infant of its kind
or at least to one that was crack-brained, unless the soul of brutes were of a
nature wholly different from ours. And we ought not to confound speech with the
natural movements which indicate the passions, and can be imitated by machines
as well as manifested by animals; nor must it be thought with certain of the
ancients, that the brutes speak, although we do not understand their language.
For if such were the case, since they are endowed with many organs analogous to
ours, they could as easily communicate their thoughts to us as to their
fellows. It is also very worthy of remark, that, though there are many animals
which manifest more industry than we in certain of their actions, the same
animals are yet observed to show none at all in many others: so that the
circumstance that they do better than we does not prove that they are endowed with
mind, for it would thence follow that they possessed greater reason than any of
us, and could surpass us in all things; on the contrary, it rather proves that
they are destitute of reason, and that it is nature which acts in them
according to the disposition of their organs: thus it is seen, that a clock
composed only of wheels and weights can number the hours and measure time more
exactly than we with all our skin.

I had after this described the
reasonable soul, and shown that it could by no means be educed from the power
of matter, as the other things of which I had spoken, but that it must be
expressly created; and that it is not sufficient that it be lodged in the human
body exactly like a pilot in a ship, unless perhaps to move its members, but
that it is necessary for it to be joined and united more closely to the body,
in order to have sensations and appetites similar to ours, and thus constitute
a real man. I here entered, in conclusion, upon the subject of the soul at
considerable length, because it is of the greatest moment: for after the error
of those who deny the existence of God, an error which I think I have already
sufficiently refuted, there is none that is more powerful in leading feeble
minds astray from the straight path of virtue than the supposition that the
soul of the brutes is of the same nature with our own; and consequently that
after this life we have nothing to hope for or fear, more than flies and ants;
in place of which, when we know how far they differ we much better comprehend
the reasons which establish that the soul is of a nature wholly independent of
the body, and that consequently it is not liable to die with the latter and,
finally, because no other causes are observed capable of destroying it, we are
naturally led thence to judge that it is immortal.

PART VI

Three years have now elapsed since
I finished the treatise containing all these matters; and I was beginning to
revise it, with the view to put it into the hands of a printer, when I learned
that persons to whom I greatly defer, and whose authority over my actions is
hardly less influential than is my own reason over my thoughts, had condemned a
certain doctrine in physics, published a short time previously by another
individual to which I will not say that I adhered, but only that, previously to
their censure I had observed in it nothing which I could imagine to be
prejudicial either to religion or to the state, and nothing therefore which
would have prevented me from giving expression to it in writing, if reason had
persuaded me of its truth; and this led me to fear lest among my own doctrines
likewise some one might be found in which I had departed from the truth,
notwithstanding the great care I have always taken not to accord belief to new
opinions of which I had not the most certain demonstrations, and not to give
expression to aught that might tend to the hurt of any one. This has been
sufficient to make me alter my purpose of publishing them; for although the
reasons by which I had been induced to take this resolution were very strong,
yet my inclination, which has always been hostile to writing books, enabled me
immediately to discover other considerations sufficient to excuse me for not
undertaking the task. And these reasons, on one side and the other, are such,
that not only is it in some measure my interest here to state them, but that of
the public, perhaps, to know them.

I have never made much account of
what has proceeded from my own mind; and so long as I gathered no other
advantage from the method I employ beyond satisfying myself on some
difficulties belonging to the speculative sciences, or endeavoring to regulate
my actions according to the principles it taught me, I never thought myself
bound to publish anything respecting it. For in what regards manners, every one
is so full of his own wisdom, that there might be found as many reformers as
heads, if any were allowed to take upon themselves the task of mending them,
except those whom God has constituted the supreme rulers of his people or to
whom he has given sufficient grace and zeal to be prophets; and although my
speculations greatly pleased myself, I believed that others had theirs, which
perhaps pleased them still more. But as soon as I had acquired some general
notions respecting physics, and beginning to make trial of them in various
particular difficulties, had observed how far they can carry us, and how much
they differ from the principles that have been employed up to the present time,
I believed that I could not keep them concealed without sinning grievously
against the law by which we are bound to promote, as far as in us lies, the
general good of mankind. For by them I perceived it to be possible to arrive at
knowledge highly useful in life; and in room of the speculative philosophy
usually taught in the schools, to discover a practical, by means of which,
knowing the force and action of fire, water, air the stars, the heavens, and
all the other bodies that surround us, as distinctly as we know the various
crafts of our artisans, we might also apply them in the same way to all the
uses to which they are adapted, and thus render ourselves the lords and
possessors of nature. And this is a result to be desired, not only in order to
the invention of an infinity of arts, by which we might be enabled to enjoy
without any trouble the fruits of the earth, and all its comforts, but also and
especially for the preservation of health, which is without doubt, of all the
blessings of this life, the first and fundamental one; for the mind is so
intimately dependent upon the condition and relation of the organs of the body,
that if any means can ever be found to render men wiser and more ingenious than
hitherto, I believe that it is in medicine they must be sought for. It is true
that the science of medicine, as it now exists, contains few things whose
utility is very remarkable: but without any wish to depreciate it, I am
confident that there is no one, even among those whose profession it is, who
does not admit that all at present known in it is almost nothing in comparison
of what remains to be discovered; and that we could free ourselves from an
infinity of maladies of body as well as of mind, and perhaps also even from the
debility of age, if we had sufficiently ample knowledge of their causes, and of
all the remedies provided for us by nature. But since I designed to employ my
whole life in the search after so necessary a science, and since I had fallen
in with a path which seems to me such, that if any one follow it he must
inevitably reach the end desired, unless he be hindered either by the shortness
of life or the want of experiments, I judged that there could be no more
effectual provision against these two impediments than if I were faithfully to
communicate to the public all the little I might myself have found, and incite
men of superior genius to strive to proceed farther, by contributing, each
according to his inclination and ability, to the experiments which it would be
necessary to make, and also by informing the public of all they might discover,
so that, by the last beginning where those before them had left off, and thus
connecting the lives and labours of many, we might collectively proceed much
farther than each by himself could do.

I remarked, moreover, with respect
to experiments, that they become always more necessary the more one is advanced
in knowledge; for, at the commencement, it is better to make use only of what
is spontaneously presented to our senses, and of which we cannot remain
ignorant, provided we bestow on it any reflection, however slight, than to
concern ourselves about more uncommon and recondite phenomena: the reason of
which is, that the more uncommon often only mislead us so long as the causes of
the more ordinary are still unknown; and the circumstances upon which they depend
are almost always so special and minute as to be highly difficult to detect.
But in this I have adopted the following order: first, I have essayed to find
in general the principles, or first causes of all that is or can be in the
world, without taking into consideration for this end anything but God himself
who has created it, and without educing them from any other source than from
certain germs of truths naturally existing in our minds In the second place, I
examined what were the first and most ordinary effects that could be deduced
from these causes; and it appears to me that, in this way, I have found
heavens, stars, an earth, and even on the earth water, air, fire, minerals, and
some other things of this kind, which of all others are the most common and
simple, and hence the easiest to know. Afterwards when I wished to descend to
the more particular, so many diverse objects presented themselves to me, that I
believed it to be impossible for the human mind to distinguish the forms or
species of bodies that are upon the earth, from an infinity of others which
might have been, if it had pleased God to place them there, or consequently to
apply them to our use, unless we rise to causes through their effects, and
avail ourselves of many particular experiments. Thereupon, turning over in my
mind I the objects that had ever been presented to my senses I freely venture
to state that I have never observed any which I could not satisfactorily
explain by the principles had discovered. But it is necessary also to confess
that the power of nature is so ample and vast, and these principles so simple
and general, that I have hardly observed a single particular effect which I
cannot at once recognize as capable of being deduced in man different modes
from the principles, and that my greatest difficulty usually is to discover in
which of these modes the effect is dependent upon them; for out of this
difficulty cannot otherwise extricate myself than by again seeking certain
experiments, which may be such that their result is not the same, if it is in
the one of these modes at we must explain it, as it would be if it were to be
explained in the other. As to what remains, I am now in a position to discern,
as I think, with sufficient clearness what course must be taken to make the
majority those experiments which may conduce to this end: but I perceive
likewise that they are such and so numerous, that neither my hands nor my
income, though it were a thousand times larger than it is, would be sufficient
for them all; so that according as henceforward I shall have the means of
making more or fewer experiments, I shall in the same proportion make greater
or less progress in the knowledge of nature. This was what I had hoped to make
known by the treatise I had written, and so clearly to exhibit the advantage
that would thence accrue to the public, as to induce all who have the common
good of man at heart, that is, all who are virtuous in truth, and not merely in
appearance, or according to opinion, as well to communicate to me the experiments
they had already made, as to assist me in those that remain to be made.

But since that time other reasons
have occurred to me, by which I have been led to change my opinion, and to
think that I ought indeed to go on committing to writing all the results which
I deemed of any moment, as soon as I should have tested their truth, and to
bestow the same care upon them as I would have done had it been my design to
publish them. This course commended itself to me, as well because I thus
afforded myself more ample inducement to examine them thoroughly, for doubtless
that is always more narrowly scrutinized which we believe will be read by many,
than that which is written merely for our private use (and frequently what has
seemed to me true when I first conceived it, has appeared false when I have set
about committing it to writing), as because I thus lost no opportunity of
advancing the interests of the public, as far as in me lay, and since thus
likewise, if my writings possess any value, those into whose hands they may
fall after my death may be able to put them to what use they deem proper. But I
resolved by no means to consent to their publication during my lifetime, lest
either the oppositions or the controversies to which they might give rise, or even
the reputation, such as it might be, which they would acquire for me, should be
any occasion of my losing the time that I had set apart for my own improvement.
For though it be true that every one is bound to promote to the extent of his
ability the good of others, and that to be useful to no one is really to be
worthless, yet it is likewise true that our cares ought to extend beyond the
present, and it is good to omit doing what might perhaps bring some profit to
the living, when we have in view the accomplishment of other ends that will be
of much greater advantage to posterity. And in truth, I am quite willing it
should be known that the little I have hitherto learned is almost nothing in
comparison with that of which I am ignorant, and to the knowledge of which I do
not despair of being able to attain; for it is much the same with those who
gradually discover truth in the sciences, as with those who when growing rich
find less difficulty in making great acquisitions, than they formerly
experienced when poor in making acquisitions of much smaller amount. Or they
may be compared to the commanders of armies, whose forces usually increase in
proportion to their victories, and who need greater prudence to keep together
the residue of their troops after a defeat than after a victory to take towns
and provinces. For he truly engages in battle who endeavors to surmount all the
difficulties and errors which prevent him from reaching the knowledge of truth,
and he is overcome in fight who admits a false opinion touching a matter of any
generality and importance, and he requires thereafter much more skill to
recover his former position than to make great advances when once in possession
of thoroughly ascertained principles. As for myself, if I have succeeded in discovering
any truths in the sciences (and I trust that what is contained in this volume 1
will show that I have found some), I can declare that they are but the
consequences and results of five or six principal difficulties which I have
surmounted, and my encounters with which I reckoned as battles in which victory
declared for me. I will not hesitate even to avow my belief that nothing
further is wanting to enable me fully to realize my designs than to gain two or
three similar victories; and that I am not so far advanced in years but that,
according to the ordinary course of nature, I may still have sufficient leisure
for this end. But I conceive myself the more bound to husband the time that
remains the greater my expectation of being able to employ it aright, and I
should doubtless have much to rob me of it, were I to publish the principles of
my physics: for although they are almost all so evident that to assent to them
no more is needed than simply to understand them, and although there is not one
of them of which I do not expect to be able to give demonstration, yet, as it
is impossible that they can be in accordance with all the diverse opinions of
others, I foresee that I should frequently be turned aside from my grand
design, on occasion of the opposition which they would be sure to awaken.

It may be said, that these
oppositions would be useful both in making me aware of my errors, and, if my
speculations contain anything of value, in bringing others to a fuller
understanding of it; and still farther, as many can see better than one, in
leading others who are now beginning to avail themselves of my principles, to
assist me in turn with their discoveries. But though I recognize my extreme
liability to error, and scarce ever trust to the first thoughts which occur to
me, yet-the experience I have had of possible objections to my views prevents
me from anticipating any profit from them. For I have already had frequent
proof of the judgments, as well of those I esteemed friends, as of some others
to whom I thought I was an object of indifference, and even of some whose
malignancy and envy would, I knew, determine them to endeavor to discover what
partiality concealed from the eyes of my friends. But it has rarely happened
that anything has been objected to me which I had myself altogether overlooked,
unless it were something far removed from the subject: so that I have never met
with a single critic of my opinions who did not appear to me either less
rigorous or less equitable than myself. And further, I have never observed that
any truth before unknown has been brought to light by the disputations that are
practised in the schools; for while each strives for the victory, each is much
more occupied in making the best of mere verisimilitude, than in weighing the reasons
on both sides of the question; and those who have been long good advocates are
not afterwards on that account the better judges.

As for the advantage that others
would derive from the communication of my thoughts, it could not be very great;
because I have not yet so far prosecuted them as that much does not remain to
be added before they can be applied to practice. And I think I may say without
vanity, that if there is any one who can carry them out that length, it must be
myself rather than another: not that there may not be in the world many minds
incomparably superior to mine, but because one cannot so well seize a thing and
make it one's own, when it has been learned from another, as when one has
himself discovered it. And so true is this of the present subject that, though
I have often explained some of my opinions to persons of much acuteness, who,
whilst I was speaking, appeared to understand them very distinctly, yet, when
they repeated them, I have observed that they almost always changed them to
such an extent that I could no longer acknowledge them as mine. I am glad, by
the way, to take this opportunity of requesting posterity never to believe on
hearsay that anything has proceeded from me which has not been published by
myself; and I am not at all astonished at the extravagances attributed to those
ancient philosophers whose own writings we do not possess; whose thoughts,
however, I do not on that account suppose to have been really absurd, seeing
they were among the ablest men of their times, but only that these have been
falsely represented to us. It is observable, accordingly, that scarcely in a
single instance has any one of their disciples surpassed them; and I am quite
sure that the most devoted of the present followers of Aristotle would think
themselves happy if they had as much knowledge of nature as he possessed, were
it even under the condition that they should never afterwards attain to higher.
In this respect they are like the ivy which never strives to rise above the
tree that sustains it, and which frequently even returns downwards when it has
reached the top; for it seems to me that they also sink, in other words, render
themselves less wise than they would be if they gave up study, who, not
contented with knowing all that is intelligibly explained in their author,
desire in addition to find in him the solution of many difficulties of which he
says not a word, and never perhaps so much as thought. Their fashion of
philosophizing, however, is well suited to persons whose abilities fall below
mediocrity; for the obscurity of the distinctions and principles of which they
make use enables them to speak of all things with as much confidence as if they
really knew them, and to defend all that they say on any subject against the
most subtle and skillful, without its being possible for any one to convict
them of error. In this they seem to me to be like a blind man, who, in order to
fight on equal terms with a person that sees, should have made him descend to
the bottom of an intensely dark cave: and I may say that such persons have an
interest in my refraining from publishing the principles of the philosophy of
which I make use; for, since these are of a kind the simplest and most evident,
I should, by publishing them, do much the same as if I were to throw open the
windows, and allow the light of day to enter the cave into which the combatants
had descended. But even superior men have no reason for any great anxiety to
know these principles, for if what they desire is to be able to speak of all
things, and to acquire a reputation for learning, they will gain their end more
easily by remaining satisfied with the appearance of truth, which can be found
without much difficulty in all sorts of matters, than by seeking the truth
itself which unfolds itself but slowly and that only in some departments, while
it obliges us, when we have to speak of others, freely to confess our
ignorance. If, however, they prefer the knowledge of some few truths to the
vanity of appearing ignorant of none, as such knowledge is undoubtedly much to
be preferred, and, if they choose to follow a course similar to mine, they do
not require for this that I should say anything more than I have already said
in this discourse. For if they are capable of making greater advancement than I
have made, they will much more be able of themselves to discover all that I
believe myself to have found; since as I have never examined aught except in
order, it is certain that what yet remains to be discovered is in itself more
difficult and recondite, than that which I have already been enabled to find,
and the gratification would be much less in learning it from me than in
discovering it for themselves. Besides this, the habit which they will acquire,
by seeking first what is easy, and then passing onward slowly and step by step
to the more difficult, will benefit them more than all my instructions. Thus,
in my own case, I am persuaded that if I had been taught from my youth all the
truths of which I have since sought out demonstrations, and had thus learned
them without labour, I should never, perhaps, have known any beyond these; at
least, I should never have acquired the habit and the facility which I think I
possess in always discovering new truths in proportion as I give myself to the
search. And, in a single word, if there is any work in the world which cannot
be so well finished by another as by him who has commenced it, it is that at
which I labour.

It is true, indeed, as regards the
experiments which may conduce to this end, that one man is not equal to the
task of making them all; but yet he can advantageously avail himself, in this
work, of no hands besides his own, unless those of artisans, or parties of the
same kind, whom he could pay, and whom the hope of gain (a means of great
efficacy) might stimulate to accuracy in the performance of what was prescribed
to them. For as to those who, through curiosity or a desire of learning, of
their own accord, perhaps, offer him their services, besides that in general
their promises exceed their performance, and that they sketch out fine designs
of which not one is ever realized, they will, without doubt, expect to be
compensated for their trouble by the explication of some difficulties, or, at
least, by compliments and useless speeches, in which he cannot spend any
portion of his time without loss to himself. And as for the experiments that
others have already made, even although these parties should be willing of
themselves to communicate them to him (which is what those who esteem them secrets
will never do), the experiments are, for the most part, accompanied with so
many circumstances and superfluous elements, as to make it exceedingly
difficult to disentangle the truth from its adjuncts- besides, he will find
almost all of them so ill described, or even so false (because those who made
them have wished to see in them only such facts as they deemed conformable to
their principles), that, if in the entire number there should be some of a
nature suited to his purpose, still their value could not compensate for the
time what would be necessary to make the selection. So that if there existed
any one whom we assuredly knew to be capable of making discoveries of the
highest kind, and of the greatest possible utility to the public; and if all other
men were therefore eager by all means to assist him in successfully prosecuting
his designs, I do not see that they could do aught else for him beyond
contributing to defray the expenses of the experiments that might be necessary;
and for the rest, prevent his being deprived of his leisure by the unseasonable
interruptions of any one. But besides that I neither have so high an opinion of
myself as to be willing to make promise of anything extraordinary, nor feed on
imaginations so vain as to fancy that the public must be much interested in my
designs; I do not, on the other hand, own a soul so mean as to be capable of
accepting from any one a favor of which it could be supposed that I was
unworthy.

These considerations taken
together were the reason why, for the last three years, I have been unwilling
to publish the treatise I had on hand, and why I even resolved to give
publicity during my life to no other that was so general, or by which the
principles of my physics might be understood. But since then, two other reasons
have come into operation that have determined me here to subjoin some
particular specimens, and give the public some account of my doings and
designs. Of these considerations, the first is, that if I failed to do so, many
who were cognizant of my previous intention to publish some writings, might
have imagined that the reasons which induced me to refrain from so doing, were
less to my credit than they really are; for although I am not immoderately
desirous of glory, or even, if I may venture so to say, although I am averse
from it in so far as I deem it hostile to repose which I hold in greater
account than aught else, yet, at the same time, I have never sought to conceal
my actions as if they were crimes, nor made use of many precautions that I
might remain unknown; and this partly because I should have thought such a
course of conduct a wrong against myself, and partly because it would have
occasioned me some sort of uneasiness which would again have been contrary to
the perfect mental tranquillity which I court. And forasmuch as, while thus
indifferent to the thought alike of fame or of forgetfulness, I have yet been
unable to prevent myself from acquiring some sort of reputation, I have thought
it incumbent on me to do my best to save myself at least from being ill-spoken
of. The other reason that has determined me to commit to writing these
specimens of philosophy is, that I am becoming daily more and more alive to the
delay which my design of self-instruction suffers, for want of the infinity of
experiments I require, and which it is impossible for me to make without the
assistance of others: and, without flattering myself so much as to expect the
public to take a large share in my interests, I am yet unwilling to be found so
far wanting in the duty I owe to myself, as to give occasion to those who shall
survive me to make it matter of reproach against me some day, that I might have
left them many things in a much more perfect state than I have done, had I not
too much neglected to make them aware of the ways in which they could have
promoted the accomplishment of my designs.

And I thought that it was easy for
me to select some matters which should neither be obnoxious to much
controversy, nor should compel me to expound more of my principles than I
desired, and which should yet be sufficient clearly to exhibit what I can or
cannot accomplish in the sciences. Whether or not I have succeeded in this it
is not for me to say; and I do not wish to forestall the judgments of others by
speaking myself of my writings; but it will gratify me if they be examined,
and, to afford the greater inducement to this I request all who may have any
objections to make to them, to take the trouble of forwarding these to my
publisher, who will give me notice of them, that I may endeavor to subjoin at
the same time my reply; and in this way readers seeing both at once will more
easily determine where the truth lies; for I do not engage in any case to make
prolix replies, but only with perfect frankness to avow my errors if I am
convinced of them, or if I cannot perceive them, simply to state what I think
is required for defense of the matters I have written, adding thereto no
explication of any new matte that it may not be necessary to pass without end
from one thing to another.

If some of the matters of which I
have spoken in the beginning of the "Dioptrics" and
"Meteorics" should offend at first sight, because I call them
hypotheses and seem indifferent about giving proof of them, I request a patient
and attentive reading of the whole, from which I hope those hesitating will
derive satisfaction; for it appears to me that the reasonings are so mutually
connected in these treatises, that, as the last are demonstrated by the first
which are their causes, the first are in their turn demonstrated by the last
which are their effects. Nor must it be imagined that I here commit the fallacy
which the logicians call a circle; for since experience renders the majority of
these effects most certain, the causes from which I deduce them do not serve so
much to establish their reality as to explain their existence; but on the
contrary, the reality of the causes is established by the reality of the
effects. Nor have I called them hypotheses with any other end in view except
that it may be known that I think I am able to deduce them from those first
truths which I have already expounded; and yet that I have expressly determined
not to do so, to prevent a certain class of minds from thence taking occasion
to build some extravagant philosophy upon what they may take to be my
principles, and my being blamed for it. I refer to those who imagine that they
can master in a day all that another has taken twenty years to think out, as
soon as he has spoken two or three words to them on the subject; or who are the
more liable to error and the less capable of perceiving truth in very
proportion as they are more subtle and lively. As to the opinions which are
truly and wholly mine, I offer no apology for them as new, -- persuaded as I am
that if their reasons be well considered they will be found to be so simple and
so conformed, to common sense as to appear less extraordinary and less
paradoxical than any others which can be held on the same subjects; nor do I
even boast of being the earliest discoverer of any of them, but only of having
adopted them, neither because they had nor because they had not been held by
others, but solely because reason has convinced me of their truth.

Though artisans may not be able at
once to execute the invention which is explained in the "Dioptrics,"
I do not think that any one on that account is entitled to condemn it; for
since address and practice are required in order so to make and adjust the
machines described by me as not to overlook the smallest particular, I should
not be less astonished if they succeeded on the first attempt than if a person
were in one day to become an accomplished performer on the guitar, by merely
having excellent sheets of music set up before him. And if I write in French,
which is the language of my country, in preference to Latin, which is that of
my preceptors, it is because I expect that those who make use of their
unprejudiced natural reason will be better judges of my opinions than those who
give heed to the writings of the ancients only; and as for those who unite good
sense with habits of study, whom alone I desire for judges, they will not, I
feel assured, be so partial to Latin as to refuse to listen to my reasonings
merely because I expound them in the vulgar tongue.

In conclusion, I am unwilling here
to say anything very specific of the progress which I expect to make for the
future in the sciences, or to bind myself to the public by any promise which I
am not certain of being able to fulfill; but this only will I say, that I have
resolved to devote what time I may still have to live to no other occupation
than that of endeavoring to acquire some knowledge of Nature, which shall be of
such a kind as to enable us therefrom to deduce rules in medicine of greater
certainty than those at present in use; and that my inclination is so much
opposed to all other pursuits, especially to such as cannot be useful to some
without being hurtful to others, that if, by any circumstances, I had been
constrained to engage in such, I do not believe that I should have been able to
succeed. Of this I here make a public declaration, though well aware that it
cannot serve to procure for me any consideration in the world, which, however,
I do not in the least affect; and I shall always hold myself more obliged to
those through whose favor I am permitted to enjoy my retirement without
interruption than to any who might offer me the highest earthly preferments.

-THE END-