§ 1. Introductory.—There are two general theories of mental development of great historical importance. One of them—the "Faculty Psychology"—may be pronounced obsolete; and the other—Associationism—is at least obsolescent. But the ways of speaking and thinking which these theories presuppose have obtained such a hold on the popular mind, and, so far as they are false, they represent fallacies so natural, that it is worth while to give a critical account of them.

§ 2. The "Faculty Psychology"—"An individual fact is said to be explained by pointing out its cause, that is, by stating the law or laws of causation of which its production is an instance. Thus a conflagration is explained, when it is proved to have arisen from a spark falling into the midst of a heap of combustibles. And in a similar manner, a law or uniformity in nature is said to be explained when another law or laws are pointed out, of which that law itself is but a case, and from which it could be deduced."* Now a law of causation states a relation between two terms,—cause and effect, antecedent process and resulting product. Each of these must have a character of its own, by which it can be definitely conceived and described. Where this condition is not fulfilled there is no causal law, and explanation is impossible. An effect cannot be its own cause, and cannot, therefore, afford its own explanation. But it is a fallacy of not infrequent occurrence to assign as a cause what turns out on examination to be only the effect itself, expressed in different language. This is a special case of the fallacy called "argument in a circle," and it usually consists in adducing as the cause of a special fact the general conception under which it is comprehended. The classical instance of this confusion is the reply of Moliere's physician to the question, tlWhy does opium produce sleep? " "Opium," he answers, "produces sleep because it has a soporific tendency." It is to be noted that the fallacy does not lie in reducing the particular to the general, for this is the form assumed by all explanation. The generalised effect (soporific virtue) is adduced as the cause of the special effect (the production of sleep by opium). But in order to explain, we require a generalised relation between the fact to be explained and some other fact which determines it Thus, we may explain why a person goes to sleep by his having taken opium, but not by his possession of a power of somnolescence.

* Mill, Logic, 9th edition, vol. i., p. 540.

In psychology, the fallacy we have described needs to be guarded against with special care. The form which it is apt to assume is that of referring a mental state to a corresponding "faculty." To say that an individual mind possesses a certain faculty is merely to say that it is capable of certain states or processes. To assign the faculty as a cause, or as a real condition of the states or processes, is evidently to explain in a circle, or in other words it is a mere failure to explain at all. Thus, it is futile to say that a particular voluntary decision is due to Will as a faculty. It is equally futile to say that extraordinary persistence in a voluntary decision is due to an extraordinary strength of Will, or of Willpower, or of the Faculty of Will. We explain nothing by asserting that certain mental processes in man have their source in the Faculty of Reason, or that certain other processes in lower animals have their source in the Faculty of Instinct. It may be true that conscience is a Compound Faculty including on the one hand the power of judgment, and on the other a certain susceptibility of feeling or sentiment. But such statements in no way account for the actual generation of a scruple or a twinge of conscience.*

The fallacy of what has been called "Faculty Psychology" may take either a positive or a merely negative form. A faculty may be explicitly regarded as an agency or real condition, producing its own special manifestation, and interacting with other faculties similarly conceived as agencies or real conditions. But such a position has rarely been maintained without disguise or equivocation. What we find is rather a tendency to rest satisfied with a reference of this or that state or process to a corresponding faculty without pushing the inquiry further so as to raise the question of causal explanation. Reference to a faculty, though it is futile from the point of view of causal explanation, may none the less have a good and useful meaning from another point of view,—that of classification. Now some kind of classification is a primary necessity for the psychologist. To divide and arrange the various and fluctuating modes of consciousness in a distinct and orderly manner, so that each may receive an appropriate name,— this is in itself no small achievement. Many of the earlier psychologists were so absorbed in inquiries of this nature that they ignored the need for discussing questions of origin and development. They tacitly assumed that the whole problem was one of classification. If they had held and expressed this view with full distinctness, there would have been no ground for charging them with a fallacy of confusion, and the Faculty Psychology could not be justly used as a term of reproach. But they were by no means completely clear as to their own position. They did not fully realize that they were only classifying and not explaining. They would probably have repudiated the charge that they treated faculties as real agencies if the charge had been distinctly formulated. But none the less, they frequently used language which implied causal relation both between faculty and special process and between different faculties.

* Locke, in criticising the phrase, "freedom of the will," has brought out very clearly the nature of this fallacy. "We may as properly say, that it is the singing faculty sings, and the dancing faculty dances, as that the will chooses, or that the understanding conceives; or, as is usual that the will directs the understanding, or the understanding obeys, or obeys not the will; it being altogether as proper and intelligible to say that the power of speaking directs the power of singing, or the power of singing obeys or disobeys the power of speaking." Essay on Human Understanding, bk. ii., ch. 21, § 17.

Indulgence in such modes of expression had a disastrous effect. It created an appearance of explanation without the reality, and in this way seriously retarded the progress of knowledge. For this reason the word "faculty" has almost passed out of use in modern psychology. But the fallacy does not necessarily disappear with the word in which it has so often found expression. We are by no means secure against it even in the present day. It is, therefore, necessary to warn the student against this peculiar mode of explanation in a circle, and to insist on the necessity of real explanation by definite conditions, giving rise to definite results, according to a fixed order.