... as I then desired to
give my attention solely to the search after truth, I thought 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 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 ... 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.
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.
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