and states, and their co-existence. As regards the matter that is judged: The meaning of the judgment 2 × 2 = 4 is not something mental, not something that arises and transpires in a stream of mental occurrences along with such things as sense impressions and moods. The meaning does not go on for a period of time and then disappear. This content of the judgment, the content of the proposition—in a word, the proposition itself—is what is valid, what is the truth as such. At most, what is mental is the act of performing the judgment or performing the statement of the judgment. The judgment’s adjudged content, that which is stated to be true, is not an empirical mental event. It is something non-empirical. It is ideal being, validity.
The basic error of psychologism is that it interprets the principle of contradiction as a statement about [47] empirical mental events and is blind to the real meaning of the principle. The principle asserts something about ideal being, about the possibility and impossibility of truths to have validity when taken together. It intends ideal relations between truths, and not relations of empirical facts and events in nature, be they mental or physical; it can simply never be a law of nature, a law of real being.
β) Psychologism misunderstands the fundamental distinction between the empirical being of the act of judging and the ideal validity of judged content. Corresponding to that, there is the misunderstanding of the kind of lawfulness that goes with each case. The lawfulness of the principle of contradiction is not an empirical lawfulness but an ideal one, and its necessity is not some empirical constraint but a normative regulation.
The law says nothing about the empirical, causal dependence of acts of thought upon each other (Wundt). The principle says nothing about the law-governed being of temporal, individual mental events running their course in the mind. It is not a law about empirical facts but says something about the intrinsically and eternally valid subsistence of truths, and the eternal impossibility of some of them being held together, be they actually performed or not. The laws not only do not govern mental events, they do not even presuppose them.
γ) Because the meaning of natural laws is that they pertain to empirical facts, they also can get their foundation only from these facts—that is, only by observing and surveying such facts—by way of induction. As regards their validity all these laws, even the most general ones like the law of gravity, are fundamentally only probable, even if this probability is of the highest order.
As empirical laws, their defining mark is to be probable. They never get free of this limitation which constantly and essentially goes with them and which says: “So far as we have observed and as long as [48] further experience does not contradict the probable law . . .” On the