complex, they say, that if they occurred in an animal, for example, we would unhesitatingly call them mental. They are of course physiological, hut it is hard to explain their apparent intelligence without supposing that they are mental as well. The conflict is very like that now waging between the two schools of animal psychologists, those who would reduce everything in the life of the animal to a series of mechanical reflexes, and those who look for signs of conscious intelligence. Like this conflict, too, it is one which can never be decided by introspection, it is only as results accumulate that the balance will swing to one side or the other. In accordance with the law of economy that regulates scientific thinking, it would seem that such activities ought to be explained in physiological terms if it is possible to do so; in this ease the question becomes: are they too complex to be so explained?
The thing of all others most needful here, then, would seem to be more evidence as to the nature of such unconscious activities. Such a body of evidence has been brought forward by Professor Freud, of Vienna, whose work is just beginning to be known in this country. Professor Freud is primarily an alienist, a former student of Charcot at the Salpétriêre. In the course of a long practise with neurotic patients, he has arrived gradually at theories of the mechanism of the unconscious, which, if they are substantiated, will go far to revolutionize present psychological conceptions.
Freud's theory is unique in that he supposes the region of the unconscious to be built up of two distinct layers, and that he would explain all the facts of unconscious action as due to the interaction of these two layers.
The upper layer is a sort of vestibule to consciousness. When, for example, as in the case cited above, we try in vain to recall a name, and later find it coming of itself into consciousness, Freud would explain the case as follows: The train of conscious activity set up by the effort has, as soon as attention was turned away from it, sunk below the threshold of consciousness. But it does not at once die away. The activity rather goes on exactly as though it were in consciousness, new associative connections are made, and by and by the associative train succeeds in reaching the name of which we were in search. This now appears in consciousness, seemingly out of all associative connection, and yet a train of association has led to its discovery, only it was a train of unconscious association. So during the day we break off scores of trains of thought without carrying them to a conclusion, because they are too trivial, too complex, too unwelcome, to occupy the mind further. Such trains of thought drop below the threshold, and there may form new associative connections. If these are strong enough, they may again appear above the threshold, apparently without cause. If such connections are not formed readily, the activity may die out without
