THOUGHT AND EXISTENCE.--DESCARTES' PRINCIPLE.
163. Am I certain that I exist? Yes. Can I prove it? No. Proof supposes
reasoning; there is no solid reasoning without a firm principle on
which to rest it; and there is no firm principle unless we suppose the
existence of the reasoning being.
In effect, if he who reasons is not certain of his own existence,
he cannot be certain of his own reasoning, since there will be no
reasoning if there be no one to reason. Therefore there are, unless
we suppose this, no principles on which to rest; there is nothing but
illusion, or rather there is neither any illusion, for there can be
none where there is no one illuded.
Our existence cannot be demonstrated: we have so clear and strong
a consciousness of it that it leaves us no uncertainty; but it is
impossible to prove it by reasoning.
164. It is a prejudice and a fatal error to believe ourselves able to
prove everything by the use of reason; the principles on which it is
founded are prior to its use; the existence of reason, and that of the
being that reasons, are prior to both.
Not only are not all things demonstrated, but it may even be
demonstrated that some things are indemonstrable. Demonstration
is a ratiocination in which we infer from evident propositions, a
proposition evidently connected with them. If the premises are of
themselves evident, they do not admit of demonstration; if we suppose
them in their turn demonstrable, we shall have the same difficulty with
respect to those on which the new demonstration is founded; therefore
we must either stop at an indemonstrable point, or proceed to infinity,
which would be never to finish the demonstration.
165. And it is to be remarked that indemonstrability does not belong
solely to certain premises; it is found, in some measure, in every
argument by its very nature, abstracting the propositions which compose
it. We know that the premises A and B are certain; from them we infer
the proposition C. By what right? Because we see that C is connected
with A and B. But how do we know this? If by immediate evidence,
by intuition, here is something else that cannot be demonstrated,
the connection of the conclusion with the premises. If by argument,
ratiocination, establishing ourselves on the art of reasoning, there
are two considerations, both tending to demonstrate indemonstrability.
I. If the principles of the art are indemonstrable, we have at once
something indemonstrable; if they are demonstrable, we must make use
of others which serve as their basis, and at last either come to one
which does not admit of demonstration, or else proceed to infinity.
II. How do we know the principles of reasoning to be applicable to
this case? By another act of reasoning? Then we shall encounter the
same difficulty as in the other case. Is it because we see that it
is so? because it is immediately evident? Then here again we have an
indemonstrable point. These reflections will clearly show that to
demand proof of everything is to demand what is impossible.
166. A being which does not think has no consciousness of itself: the
stone exists, but does not know that it exists, neither would man
himself in a similar case, were all his intellectual and sensible
faculties in complete inaction. We easily conceive the difference of
these two states by calling to mind what occurs, when from waking we
pass into a profound sleep, and again when we awake from it. The first
starting-point of our cognitions is this intimate presence of our
internal acts, abstraction made of the questions which may be raised
upon their nature. If every thing existed as at present, and there also
existed, besides the world which we see, infinite other worlds, not
even then would any thing exist for us, had we not those internal acts
of which we are speaking. We should be like an insensible body placed
in the immensity of space, which would suffer no mutation were every
thing around it to disappear, and would perceive no change even if it
were itself to sink into the abyss of nothing. On the other hand, if
we suppose every thing to be annihilated except this being within us
which feels, thinks, and wills, there still remains a point whereon
to base the edifice of human cognitions: this being, though alone in
immensity, would render itself an account of its own acts to the
extent of its ability, and might go into numberless combinations having
for their object the possible though not the real.
167. The famous principle of Descartes, _I think, therefore I am_,
has been often attacked, and justly and conclusively so, if this
philosopher really understood his principle in the sense which the
schools are accustomed to give it. If Descartes presented it as a
true argument, as an enthymema with an antecedent and a consequent,
the argument was clearly defective in its foundation. For when he
said, "I am going to prove my existence with this enthymema: I think,
therefore I am:" this objection might have been made; your enthymema is
equivalent to a syllogism in this form: whatever thinks, exists; but
I think; therefore, I exist. This syllogism, in the supposition of a
universal doubt, excluding even the supposition of existence itself, is
inadmissable in its propositions and in their connection. In the first
place, how do you know that whatever thinks exists? Because nothing can
think without existing. How do you know that? Because what does not
exist, does not act. But how in its turn do you know this? Supposing
every thing to be doubted, nothing to be known, these principles are
not known; otherwise we fall short of the supposition of universal
doubt, and consequently go out of the question. If any one of these
principles must be admitted without proof, it is just as well to admit
your own existence and save yourself the trouble of proving it with an
enthymema.
In the second place, how do you know that you think? Your argument may
be retorted, as dialecticians say, in the following manner: nothing can
think without existing; but your existence is doubtful, for you are
trying to prove it; therefore you are not sure that you think.
168. Manifestly, then, Descartes' principle, taken as a true argument,
cannot be defended; and it is so easy to see its defect, that it seems
impossible for so clear and penetrating an intellect to have overlooked
it. It is therefore probable that Descartes understood his principle in
a very different sense; and we will now briefly show what meaning, in
our judgment, the illustrious philosopher must have given to it.
Supposing himself for a moment in universal doubt, without accepting
for certain anything that is known, he concentrated himself on himself,
and in the depth of his soul sought a point whereon to base the edifice
of human cognitions. Although we abstract all around us, we clearly
cannot abstract ourselves, our mind, which is present to its own eyes,
only the more lucidly, the greater the abstraction in which we place
ourselves with respect to eternal objects. Now in this concentration,
this collection of himself within himself, this withdrawal from every
thing for fear of error, and asking himself if there be any thing
certain, if there be any foundation and starting-point in the career
of knowledge; first of all is presented to him the consciousness of
thought, the very presence of the acts of his mind. If we mistake
not, this was Descartes' thought: I wish to doubt of every thing; I
refrain from affirming as from denying any thing; I isolate myself from
whatever surrounds me, because I know not if it be any thing more than
an illusion. But in this very isolation, I meet with the intimate sense
of my internal acts, with the presence of my mind; I think, therefore
I am; this I feel in a manner that leaves no room for doubt or
uncertainty; therefore, I am; that is to say, this sense of my thought
makes me know my existence.
169. This explains why Descartes did not present his principle as a
mere enthymema, as an ordinary argument, but as determining a fact
presented to him and first in the order of facts: even if he inferred
existence from thought, it was not by deduction, properly so called,
but as one fact contained in another, or rather identified with it.
We say _identified_, because it really is so in Descartes' opinion;
and this confirms what we have already advanced, that this philosopher
did not offer an argument, but laid down a fact. According to him,
the essence of the soul consists in thought; and as other schools of
philosophy distinguish between substance and its acts, considering
the mind in the first class, and thought in the second, so Descartes
held that there was no distinction between mind and thought, that
they were the same thing, that thought constituted the essence of the
soul. "Although one attribute," he says, "suffices to make us know the
substance, there is, nevertheless, in every substance one attribute,
which constitutes its nature and its essence, and on which all the
others depend. Extension in length, breadth, and depth, constitutes the
essence of corporeal substance; and thought constitutes the nature of
the substance which thinks."[9] From this it follows that Descartes, in
laying down the principle, _I think, therefore I exist_, only declared
a fact attested by consciousness; and so simple did he consider it, and
so unique, that in evolving his system, he identified thought with the
soul, and its essence with its existence. He was conscious of thought,
and said: "this thought is my soul; I am." It is not now our purpose
to weigh the value of this doctrine, but only to explain in what it
consists.(17)
[9] Descartes. _Principes de la Philosophie_, 1^{ière} partie.