part and also the other parts; therefore, the idea of greater than its part enters into the idea of whole. Thus it is that we must refute whoever denies this principle; and this method, better than that of argumentation, may be said to explain the terms and analyze the conceptions, for it clearly does nothing but define the former and decompose the latter.
SIXTH PROPOSITION.
211. The principle of contradiction is known only by immediate evidence.
Demonstration.—Two things are here to be proved: that the knowledge is by evidence, and that the evidence is immediate. As regards the former we will remark that the principle of contradiction is not a simple fact of consciousness, but a purely ideal truth. Every fact of consciousness involves reality, and cannot be expressed without the assertion of some existence: the principle of contradiction neither affirms nor denies any thing positive; that is, it does not say that any thing exists or does not exist; it only expresses the opposition of being to not-being, and of not-being to being, abstraction made from our taking the word being copulatively or substantively.
212. Every fact of consciousness is not only something existent, but something determinate; it is not a thought in the abstract, but is this or that thought. The principle of contradiction contains nothing determinate; it abstracts not only the existence, but also the essence of things, since it relates not only to existing things, but also to things possible: it distinguishes no species among them, but embraces them all in their greatest generality. When we say, "it is impossible for the same thing to be and not be," the word thing does not at all restrict the meaning; it expresses being in general, in its greatest indeterminateness. In the to be or not be, the word be expresses not only existence, but also every class of essences in their most complete indeterminateness. Thus the principle is equally applicable in these two propositions: it is impossible for the moon to be and not be; it is impossible for a circle to be and not be a circle; although the first is in the real order, and there the word be expresses existence, and the second is in the ideal order, and the word be expresses only the relation of predicate to subject.
213. Every fact of consciousness is individual; the principle of contradiction is the most universal imaginable: every fact of consciousness is contingent; the principle of contradiction is absolutely necessary, a necessity which is a mark of truths known by evidence.
214. The principle of contradiction is a law of all intelligence; it is of absolute necessity for the finite as for the infinite; not even the infinite intelligence is beyond this necessity, for infinite perfection cannot be an absurdity. Every fact of consciousness as purely individual, relates only to the being that experiences it; neither the order of intelligences, nor that of truth suffers any mutation from my existence or non-existence.
215. The principle of contradiction, besides the marks of necessity and universality, which distinguish truths of evidence, possesses also that of being seen with that immediate, intellectual clearness, of which we have already treated. In the idea of being we see most clearly the exclusion of not-being.
Hence the proof of the second part of the proposition: because there is immediate evidence of the relation of the predicate to the subject, when the sole idea of the subject, without the necessity of combination with other ideas, enables us to perceive this relation: this is so in the present case, for not only no combination is needed, but all combinations are impossible if the truth of this principle be not supposed.(21)
CHAPTER XXII.
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
