CONFUSION OF IDEAS IN DISPUTES ON THE FUNDAMENTAL PRINCIPLE.
160. There are, in our opinion, various principles, which, with regard
to the human intellect, may be called equally fundamental, both because
they serve as foundation in the common and scientific orders, and
because they do not rest upon any other, since it is impossible to
assign any one which enjoys this quality as an exclusive privilege.
In seeking the fundamental principle, it is customary in the schools
to observe that they do not endeavor to find a truth from which all
others emanate, but an axiom the destruction of which draws with it
that of all other truths, and the firmness of which sustains them,
at least indirectly, in such manner that whoever denies them may be
refuted by indirect demonstration, or reduction _ad absurdum_; that is,
admitting the above axiom, it may follow that whoever denies the others
will be convicted of being in opposition to one which he himself has
acknowledged to be true.
161. It has been much disputed whether this or that principle merit
the preference. We believe that there is here a confusion of ideas,
proceeding in great part from not sufficiently marking the limits of
testimonies so distinct as those of consciousness, of evidence, and of
common sense.
Descartes' famous principle, _I think, therefore I am_; that of
contradiction, _it is impossible for a thing to be and not to be at
the same time_; and what is called the principle of the Cartesians,
_whatever is contained in the clear and distinct idea of anything, may
be affirmed of it with all certainty_; are the three principles that
have divided the schools. In favor of each, reasons the most powerful,
and even conclusive against the others, considering the ground on which
the question was placed, have been brought forward.
If you are not certain that you think, argues the partisan
of Descartes, you cannot be certain even of the principle of
contradiction, or know the criterion of evidence to be valid; for
both, it is necessary to think; whoever affirms or denies anything,
thinks; without thought, neither affirmation nor negation is possible.
But let us admit thought: we have already a foundation, and one of
such a nature that we find it in ourselves, attested by consciousness,
irresistibly forcing upon us the certainty of its existence. The
foundation once laid, we see how the edifice can be raised; for this
we need not go out of our own thought; there is the luminous point to
conduct us in the path to truth; let us follow its splendor, and having
established an immovable point, let us draw from it the mysterious
thread to guide us in the labyrinth of science. Thus our principle is
the first, the basis of all others; it has sufficient power to sustain
itself, sufficient also to impart firmness to others.
This language is certainly reasonable; but it has this fault, that the
conviction which it is intended to produce, is neutralized by the not
less reasonable language of those who hold a directly contrary opinion.
One who maintains the principle of contradiction may reason thus: if
you do not admit it to be impossible for the same thing to be and not
be at the same time, it may be possible that you think and do not think
at the same time; your assertion, then, _I think_, is of no weight,
for its opposite, _I do not think_, may, at the same time, be true. In
this case, the conclusion of existence is invalid; for, even admitting
the legitimacy of the consequence, _I think, therefore I am_, as we
know on the other hand that this other premise, _I do not think_, is
possible, the deduction cannot be made. Nor is the other principle:
_whatever is contained in the clear and distinct idea of anything,
may he affirmed of it with all certainty_, of any more value without
the principle of contradiction; because if being and not-being are
possible at the same time, an idea may be clear and obscure, distinct
and confused; a predicate may be contained and not contained in the
subject; we may be certain and uncertain, affirm and deny; therefore it
is of no service.
He who argues thus seems quite reasonable; but strangely enough, the
advocate of the third principle brings equally strong arguments against
his two adversaries. How is it known, he asks, that the principle of
contradiction is true? Only because we see in the idea of being the
impossibility of its being and not being at the same time, and _vice
versa_; therefore, we are sure of the principle of contradiction
only from the application of the principle: _whatever is contained
in the clear and distinct idea of anything, may he affirmed of it
with all certainty_. If nothing can be sustained without relying
upon the principle of contradiction,--and this is based upon our
principle,--ours is the foundation of them all.
162. They are all three right, and all three wrong. They are right
in asserting that the denial of their respective principles is the
ruin of the others. They are all wrong in pretending that the denial
of the others is not the ruin of their own. Whence then the dispute?
From the confusion of ideas, by which they compare principles of very
different orders, all indeed very true, but not to be compared with
each other for the same reason that we cannot compare the white and
the warm, and dispute whether a thing has more degrees of heat or
whiteness. Comparison requires not only opposition in the extremes, but
also something in common; if things are totally unlike, comparison is
impossible.
Descartes' principle is the enunciation of a simple fact of
consciousness; that of contradiction is a truth known by evidence;
and that of the Cartesians is an assertion that the criterion of
evidence is valid, and that it is a truth of reflection expressing the
intellectual impulse by which we are borne to believe the truth of what
we know by evidence.
The importance of this question requires a special examination of each
of the three principles, which we shall make in the next chapters.(16)