The importance of Memory is recognized by all persons--whether psychologists or not. At the present time there is a growing interest in systems of memory-training offered to the public, which aim at mental efficiency as a means to success in life. Indeed, from the tone of some advertisements seen in the press, one might be prompted to think that Memory itself was the sole factor determining success in either a professional or a business career. Yet, although we are likely to regard this as a somewhat exaggerated statement, nevertheless we cannot deny the very great importance of the power of Memory. How often, in everyday life, we hear people excuse themselves by remarking "My memory failed me" or "played me false" or, more bluntly, "I forgot all about that." Without doubt, Memory is a most vital factor, though not the only one in mental efficiency.[Footnote: The true ideal of mental efficiency must include power of Will as well as of Memory.] It is an element in mental life which puzzles both the specialist in psychology and the layman. "What is this wonderfully subtle power of mind?" "How do we remember?" Even the mind, untrained in psychological investigation, cannot help asking such questions in moments of reflection; but for the psychologist they are questions of very vital significance in his science. For Bergson, as psychologist, Memory is naturally, a subject of great importance. We must note, however, that for Bergson, as metaphysician, it plays an even more important role, since his study of Memory and conclusions as to its nature lead him on to a discussion of the relation of soul and body, spirit and matter. His second large work, which appeared in 1896, bears the title Matiere et Memoire. For him, Memory is a pivot on which turns a whole scheme of relationships--material and spiritual. He wrote in 1910 a new introduction for the English Translation of this work. He there says that "among all the facts capable of throwing light on the psycho-physiological relation, those which concern Memory, whether in the normal or the pathological state, hold a privileged position." [Footnote: Introduction to Matter and Memory, p. xii.] Let us then, prior to passing on to the consideration of the problem of the relation of soul and body, examine what Bergson has to say on the subject of Memory.