These somewhat dogmatic general statements—which I have put before you much after the fashion of the lawyer who presents a general statement of his case in anticipation of the evidence—I hope will become clear and their truth evident as we proceed; likewise, their bearing upon the facts of abnormal psychology. To make them clear it will be necessary to explain in some detail the generally accepted theory of memory as a process and to cite the numerous data upon which it rests. There may be, as, indeed, you will find there are, wide differences of opinion as to the exact psychological mechanism by which a memory-process plays its part in the larger processes of mental life, normal and abnormal, such as I have just mentioned, but that the memory-process is a fundamental factor is revealed by whatever method the problems are attacked. A study, therefore, of this fundamental factor and a determination of its mechanism are a prerequisite for a study of the more complex processes in which it takes part. For this reason I shall begin the study of the Unconscious (subconscious), to which I shall ask your attention in these lectures, with a consideration of the processes of memory. If you ask the average person, as I have often done, how or why he remembers he will be puzzled and he is apt to reply, “Why, I just remember,” or, “I never thought of that before.” If you push him a bit and ask what becomes of ideas after they have passed out of mind and have given place to other ideas, and how an idea that has passed out of mind, that has gone, disappeared, can be brought back again as memory, he becomes further puzzled. We know that ideas that have passed out of mind may be voluntarily recalled, or reproduced, as memory; we may say that meantime they have become what may be called dormant. But surely something must have happened to enable these conscious experiences to be conserved in some way and recalled. Ideas are not material things which, like books, can be laid away on a shelf to be taken up again when wanted, and yet we can recall, or reproduce, many ideas when we want them just as we can go to a shelf and take down any book we want. We learn the alphabet and the multiplication table in childhood. During the greater part of our lives the sensory images, auditory language symbols, etc., which may be summarized as ideas representing these educational experiences, are out of our minds and do not form a continuous part of our conscious experiences, but they may be recalled at any moment as memory. In fact, try as hard as we may, we cannot forget our alphabet or multiplication table. Why is this?