THE CRITERION OF EVIDENCE.
239. There are two species of evidence, mediate and immediate. We
call immediate evidence that which requires only understanding of the
terms; and mediate evidence that which requires reasoning. That the
whole is greater than its part is evident by immediate evidence;
that the square of the hypothenuse is equal to the sum of the squares
of the other two sides, is known by mediate evidence, that is, by
demonstrative reasoning.
240. We have said that one of the distinctive characteristics of
evidence is the necessity and universality of its object. This is a
characteristic as well of mediate as of immediate evidence.
Besides this characteristic there is another, called with more reason
essential, notwithstanding some doubt as to whether it extends to
mediate evidence or not; it is that the idea of the predicate is
found contained in that of the subject. This is the most complete
essential notion of the criterion of immediate evidence, by which it is
distinguished from the criteria of consciousness and common sense.
We have said there is some doubt as to this characteristic extending
to mediate evidence; by this we mean that also in mediate evidence
the idea of the predicate may be contained in that of the subject. In
this it is not our intention to ignore the difference between theorems
and axioms, but to call the reader's attention to a doctrine which we
propose to develop, while treating of mediate evidence. In the present
chapter we shall only treat of evidence in general, or of immediate
evidence alone.
241. Evidence involves relation, for it implies comparison. When
the understanding does not compare, it has no evidence, but only a
perception, which is a pure fact of consciousness; and this evidence
does not refer to perception alone, but always supposes or produces a
judgment.
We find two things in every act where there is evidence: the pure
intuition of the idea, and the decomposition of this idea into various
conceptions accompanied with the perception of their mutual relations.
This we will explain by an example from geometry. The triangle has
three sides: this is an evident proposition, for in the very idea of
triangle, we find the three sides; and in conceiving the triangle, we
in some sense conceive the three sides. Had we limited ourselves to
the contemplation of the simple idea of triangle, we should have had
intuition of the idea, but not evidence, which begins only when we
find, in decomposing the conception of triangle, and considering in it
the idea of figure in general, of side, and of the number three, these
all contained in the primitive conception. Evidence consists in the
clear conception of this.
So true is this that the very nature of things makes common language
philosophical. We do not say, an idea is evident, but a judgment is: no
one calls a term evident, but a proposition only. And why? Because the
term simply expresses the idea without any relation, or decomposition
into its partial conceptions; whereas the proposition expresses the
judgment, that is, affirms or denies that one conception is contained
in another, which, in the present matter, supposes decomposition of the
entire conception.
242. Immediate evidence is the perception of identity between various
conceptions, separated by the analytical power of the intellect.
Thus identity combined in a certain way with diversity is not a
contradiction, as it might at first sight seem, but something very
natural, if we observe one of the most constant facts of our intellect,
the faculty of analyzing the most simple conceptions, and of seeing
relations between identical things.
What are all axioms? What are all propositions _per se notæ_? Nothing
but expressions, in which it is affirmed that a predicate belongs to
the essence of the subject, or is contained in its idea. The mere
conception of the subject includes the predicate: the term which
denotes the first also denotes the second; yet the intellect, with a
mysterious power of analysis, distinguishes between identical things,
and then compares them in order to make them again identical. Whoever
says triangle, expresses a figure composed of three sides and three
angles; but the intellect may take this idea and consider in it the
ideas of the number three, side, and angle, and compare them with the
primitive conception. In this distinction there is no deception; there
is only the exercise of the faculty, which regards the thing under
different aspects, in order to arrive at the intuition and affirmation
of the identity of the very things it had before distinguished.
243. Evidence is a sort of calculation of the intellect, whereby it
finds in the conception analyzed whatever was placed in the principle
or was contained in it. Hence the necessity and universality of the
object of evidence, inasmuch as, and in the manner, in which it is
expressed by the idea. To this there are no exceptions. Either a
predicate is or is not placed in a primitive principle: if it is, it is
there, according to the principle of contradiction. Either it was or
was not excluded from the conception; if the conception itself excludes
or denies it, this it does by virtue of the principle of contradiction.
Thus the more fundamental of the two characteristics of evidence given
above is, that the idea of the predicate is contained in the idea of
the subject. Hence the necessity and universality; since, in verifying
this condition, it is impossible for the predicate not to belong
_necessarily to all the subjects_.
244. Thus far we have encountered no difficulty, because we have
treated only of evidence subjectively considered, that is, as relating
to pure conceptions; but the intellect does not stop with the
conception, but extends to the object, and says not only that it sees
the thing, but that the thing is as it sees it. Thus the principle of
contradiction, considered in the purely subjective order, means that
the conception of being is opposed to that of not-being, which destroys
it, just as the conception of being destroys that of not-being; it
means, that in endeavoring to conceive jointly these two things, and
to make them co-exist, a sort of struggle of thoughts, reciprocally
annihilating each other, takes place in the depths of our soul,--a
struggle which the understanding is condemned to witness without hope
of establishing peace between the combatants. If we confine ourselves
to this phenomenon, no objection can be made. We experience it, and
there is no further question about it; but in announcing the principle,
we would announce something more than the incompatibility of the
conceptions; we would transfer this incompatibility to the things
themselves, and assert that not only our own conceptions, but also
all real and possible beings are subjected to this law. Whatever be
the object of which we treat, whatever the conditions under which we
suppose it existent or possible, we say that while it is, it cannot
not be; and while it is not it cannot be. We affirm, then, the law of
contradiction, not only for our own conceptions, but also for things
themselves; the intellect applies to every thing the law which it finds
necessary to itself.
By what right? An incontestible right, for it is the law of necessity.
With what reason? With none, for we are now at the foundation of
reason; this is the _ne plus ultra_ of the human understanding;
philosophy can go no farther. Let us not, however, be thought to
abandon the field to skeptics, or to entrench ourselves in necessity,
contented with pointing out a fact of our nature. The question is
susceptible of different solutions, which may not, indeed, go beyond
the _ne plus ultra_ of our mind, but which yet leaves the cause of
skepticism in great straits.
245. To ask why the criterion of evidence is legitimate, is to ask why
this proposition is true: "whatever is evident is true;" it is to raise
the question of the objectiveness of ideas. The fundamental difference
between dogmatists and skeptics, is not that the latter deny the facts
of consciousness,--the most refined skepticism has not come to this,
and both agree in recognizing the purely subjective appearance of
phenomena; but it is that dogmatists found science on consciousness,
and skeptics maintain that this is an illegitimate transition, and that
we must despair of science, and confine ourselves to mere consciousness.
According to this doctrine, ideas are empty forms of the understanding,
mean nothing, and can lead to nothing; although they entertain the
understanding, and offer to it an immense field for combinations, the
world they present to it is purely illusory, and can serve for nothing
in the real order. In contemplating these entirely empty forms, the
intellect is the sport of fantastic visions, from the union of which
results the spectacle which seems now to belong to reality, and now to
possibility; either it is a mere nonentity, or something, and if so, it
can never make us sure of the reality it possesses.
246. It is difficult to fight skepticism when it takes this ground:
situated beyond the domains of reason, the decisions of reason cannot
reach it. It will appeal from them all, for it begins by denying the
competency of the judge. But as these skeptics admit consciousness, it
is right that they should defend it against whoever attempts to deprive
them of it. We believe that if the objectiveness of ideas be denied,
not only all science, but also all consciousness is annihilated;
and here skeptics are guilty of an inconsequence; for, while they
deny the objectiveness of some ideas, they admit that of others. No
consciousness, properly so called, can exist, if this objectiveness be
absolutely destroyed. We beg the reader to follow us in a brief, but
severe analysis of the facts of consciousness, in their relations with
the objectiveness of ideas.(24)