The older psychology did not bother itself much with these questions which puzzle the average man. It was content for the most part with a descriptive statement of the facts of conscious memory. It did not concern itself with the process by which memory is effected; nor, so long as psychology dealt only with phases of consciousness, was it of much consequence. It has been only since subconscious processes have loomed large in psychology and have been seen to take part on the one hand in the mechanism of conscious thought and on the other to produce various bodily phenomena, that the process of memory has acquired great practical importance. For it has been seen that in these subconscious processes previous conscious experiences are resurrected to take part as subconscious memory, consequently a conscious experience that has passed out of mind may not only recur again as conscious memory, but may recur subconsciously below the threshold of awareness. The study of subconscious processes therefore necessarily includes the processes of memory. And so it has become a matter of considerable moment to follow the fate of experiences after they have passed out of mind with a view to determining the mechanism by which they can be reproduced consciously and subconsciously. More than this it is important that the theory of memory should be removed if possible from the domain of purely speculative psychological concepts and placed on a sound basis of observation and experiment like other accepted theories of science.