Concepts and Judgments being mental acts, or products of mental activity, it is often thought that Logic must be a department of Psychology.

It is recognised of course, that Psychology deals with much more than Logic does, with sensation, pleasure and pain, emotion, volition; but in the region of the intellect, especially in its most deliberate and elaborate processes, namely, conception, judgment, and reasoning, Logic and Psychology seem to occupy common ground.

In fact, however, the two sciences have little in common except a few general terms, and even these they employ in different senses.

It is usual to point out that Psychology tries to explain the subjective _processes_ of conception, judgment and reasoning, and to give their natural history; but that Logic is wholly concerned with the _results_ of such processes, with concepts, judgments and reasonings, and merely with the validity of the results, that is, with their truth or consistency; whilst Psychology has nothing to do with their validity, but only with their causes.

Besides, the logical judgment (in Formal Logic at least) is quite a different thing from the psychological: the latter involves feeling and belief, whereas the former is merely a given relation of concepts.