THE PRINCIPLE OF EVIDENCE.
216. Among the principles which, by their pretensions to the title
of fundamental, have most figured in the schools, is one called the
principle of the Cartesians: "whatever is contained in the clear and
distinct idea of any thing, may be affirmed of it with all certainty."
We have already seen Kant resuscitate this principle, although in other
words, equivocally taking it as synonymous with that of contradiction.
Upon close examination we shall easily perceive that the formula of
the Cartesians, like that of Kant, only expresses the legitimacy of
the criterion of evidence. Both may be simplified to this: evidence
is a criterion of truth; or, whatever is evident is true. As we shall
hereafter use this transformation to distinguish ideas which we
consider very confused, we will show the reason of the equality of the
two expressions.
217. To say that any thing is contained in the clear and distinct idea
of another thing, is the same as to say that there is evidence that a
predicate belongs to a subject; the words have, and can have, no other
meaning. To be contained in a clear and distinct idea, is equivalent to
seeing one thing in another by that intellectual light which we call
evidence; therefore, this expression, "whatever is contained in the
clear and distinct idea of any thing," is exactly equivalent to this,
"whatever is evident."
To say, that any thing may be affirmed of another with all certainty,
is the same as to say, "this thing is true, and we may be perfectly
certain of it." It is the truth that is affirmed, and the truth only;
therefore, this expression, "may be affirmed of it with all certainty,"
is exactly equivalent to this, "it is true."
Thus the expression of the Cartesians may be transformed into this:
"Whatever is evident is true," or its equivalent, "evidence is a sure
criterion of truth."
218. "A predicate that is opposed to a subject does not belong to it,"
is Kant's formula. The opposition here meant is that founded on ideas,
when the predicate is necessarily excluded by intrinsic _opposition_
from the idea of the subject. The expression, then, "a predicate that
is opposed to a subject," is equivalent to this: "when the predicate is
clearly seen excluded from the idea of the subject," which last is in
its turn equivalent to this: "the exclusion, or the opposition between
the subject and the predicate, is evident."
"Does not belong to it," means the same as, "it is true that it does
not belong to it;" and since these formulas have two values, one for
affirmative, another for negative cases, if we say the predicate that
is opposed to a subject does not belong to it, we may with equal reason
say, the predicate contained in the idea of a subject belongs to it;
wherefore, Kant's formula exactly coincides with this: "whatever is
evident is true."
219. This transformation gives us greater simplicity and generality;
simplicity by the very expression, and generality, because affirmative
as well as negative cases are included. The words, "whatever is
evident," embrace affirmations as well as negations, for the inclusion
of a predicate in a subject may be just as evident as their mutual
opposition. Thus, we may see one thing contained in the idea of
another, just as we may see it excluded from that idea. Under all
conceptions the formula, "whatever is evident is true," is preferable;
and if we would express it not as a principle, but as a rule to be
applied, it may be converted into this: "evidence is a sure criterion
of truth."
220. This transformation must not be supposed to be the only object
of the preceding analysis; although in these matters clearness and
precision should be carried to the highest possible point, we should
nevertheless have abstained from these considerations, had we only
proposed to make an innovation, and one perhaps of little practical
consequence; the same thing is expressed in both formulas, and he who
does not understand the first will not understand the second. Our
principal object was not, however, to make this innovation, but to
show into what a confusion of ideas those fall who inquire whether the
principle involving the legitimacy of the criterion of evidence ought,
or ought not, to be considered as fundamental, and be preferred to the
principle of contradiction, as also to that of Descartes.
221. We begin by establishing a proposition which may seem a most
strange paradox, but is far from being so: _the principle of evidence
is not evident_.
_Demonstration._--This principle in its simplest form is this: the
evident is true. This proposition, we say, is not evident. When is
a proposition evident? When we see the predicate in the idea of
the subject; and here this does not occur. _Evident_ is the same
thing as _clearly seen_, as offered to the intellect in a most lucid
manner. _True_ is the same as conformity of the idea with the object.
We now ask, can you, however much you analyze this idea, "seen with
clearness," ever find this other, "conformed to the object?" No. This
is an immense leap: we pass from subjectiveness to objectiveness; we
affirm subjective to be the reflex of objective conditions; we go from
the idea to its object, and this transition is the most transcendental,
difficult, and obscure problem of philosophy. Let the reader now decide
if we had not ground to assert that the proposition, "the principle of
evidence is not evident," was not a paradox.
222. What, then, shall we say of this proposition: "Whatever is evident
is true?" It is not an axiom, for the predicate is not contained in
the idea of the subject; it is not a demonstrable proposition, for all
demonstration rests on evident principles, and consists in deducing
from them a consequence evidently connected with them; this cannot take
place unless we presuppose the legitimacy of evidence, that is to say,
that which is the object of the demonstration. At the commencement of
the argument, it might be asked, how do you know the principle on which
your argument is based? How do you know it to be true? By evidence.
But recollect you are proving that whatever is evident is true, and,
therefore, you beg the question. The truth of the laws of logic, to
which every argument must conform, is known only by evidence; therefore
if we do not suppose whatever is evident to be true, we cannot argue at
all.
223. We hold then that the principle of evidence can be based on no
other principle, and that, consequently, it has the first mark of the
fundamental principle. If it fails, all other principles,--that of
contradiction, known like the others only by evidence, included,--fail
with it; this is another mark of the fundamental principle. Let us see
if it has the third, by aid of which, whoever denies the rest may be
refuted.
Rarely does any one deny the principle of contradiction, and admit that
of evidence; yet, making this extravagant supposition, this principle
alone would be of avail, because the question would be reduced to
this: does he admit the principles to be evident? If he does not, his
intellect is unlike that of other men; if he does, the argument brought
against him is conclusive. You admit that whatever is evident is true;
such or such a principle is evident for you, therefore it is true. The
premises are evident of themselves; the legitimacy of the consequence
is also evident; and he must consequently admit it, since he admits the
criterion of evidence to be a general rule.
224. Whence then the singularity we have noticed in this principle?
It is neither evident, nor demonstrable; it is necessary to all
others, and whoever denies them is refuted by it. Whence, then,
such a singularity? It has a very simple cause; it is, that the
principle of evidence expresses no objective truth, and therefore
is not demonstrable: it is not a simple fact of consciousness, for
it expresses the relation of the subject to the object, for which
reason it cannot be limited to the purely subjective; it is a
proposition known by a reflex act, and it expresses the primary law
of all our objective cognitions. These are founded on evidence; this
we experience: but when the mind asks why we trust evidence, we can
make no other answer than that whatever is evident is true. What
is the foundation of this proposition? Ordinarily it has none; we
conform to it without ever thinking of it; but if we take the pains to
reflect, we find three motives for assenting to it: the first is an
irresistible instinct of nature; the second is the destruction of all
our cognitions and the impossibility of thought, if we do not admit
the legitimacy of the criterion; the third is the perceiving that,
admitting this criterion, every thing is co-ordinated in the intellect,
that an ideal universe admirably harmonized, takes the place of chaos,
and that we feel possessed of the means necessary to reason and to
construct a scientific edifice in the real universe, the knowledge of
which we have from experience.(22)