or that of non-identity meaningless does so by his own fault. He must have expected to find in these propositions special ideas, a source of positive knowledge. But they are not in themselves knowledge, separate acts of thought, but the common standard for all acts of thought. And so they cannot be compared with other acts of thought. The rule of the process of thought must be outside thought. The proposition of identity does not add to our knowledge; it does not increase but rather founds a kingdom. The proposition of identity is either meaningless or means everything. Upon what do the propositions of identity and of non-identity depend? The common view is that they are judgments. Sigwart, for instance, who has recently discussed the matter, puts it as follows: The two judgments A is B and A is not B cannot be true at the same time because the judgment "An unlearned man is learned" would involve a contradiction because the predicate "learned" is affirmed of a subject of which the judg- ment has been made implicitly that he is unlearned, so that in reality two judgments are made, X is learned and X is unlearned. The "psychologismus" of this method of argument is plain. It has recourse to a temporary judgment preceding the formation of the conception "unlearned man." The proposition, however, A is not A claims validity quite apart from the past, present, or future existence of other judgments. It depends on the conception "unlearned man." It makes the conception more certain by excluding contradictory instances.
This, then, gives us the true function of the principles of identity and non-identity. They are materials for conceptions.
This function concerns only logical conceptions, but not what have been called psychological conceptions. The conception is always represented psychologically by a generalisation; and this presentation in a certain fashion is included in the conception. The generalisation represents the conception psychologically, but is not identical with it. It can, so to speak, be richer (as when 1 think of a triangle)
