Psychology affords us not the least help in this matter, for in describing memory as a faculty of the mind or the conservative faculty it does no more than present us with a name in place of our explanation. But we do get nearer realities when we go down to the organic aptitude which, in consequence of an action, there is to the recurrence of a similar action on another occasion. And physiology presents us with many illustrations of such organized aptitudes. Take, for example, the education of our movements: a designed movement is performed at first slowly and clumsily, and it is only by giving great pains to it and frequently repeating it that we acquire the skill to perform it easily and quickly; the aptitude thereto being at last so completely organized in the proper nervous centres that it may be performed without consciousness on our part, quite automatically. Thus it appears that memory in this case becomes less conscious as it becomes more complete, until, when it has reached its greatest perfection and is performed with the most facility, it is entirely unconscious. After which, if we are psychologists who are content to rest in words and forbear to pursue the facts which they denote, we must cease to speak of it as memory: it has become custom, or habit, or automatism. But if we go beneath words to the property of the motor nerve-centres whereby they react in a definite way to impressions made upon them, organically register their experience, and so acquire by education their special faculties, we perceive that we have not to do in the higher nerve-centres with fundamentally different properties of nerve element, but with different functions which depend upon the same fundamental property. Substitute the highest nerve-centres for the motor nerve-centres, and the complex idea for the complex movement, and what has been said of the latter is strictly true of the former; the idea, like the movement, is accompanied with less consciousness the more completely it is organized, and when it has been completely organized it takes its part automatically in our mental operations, being performed, as a habitual movement is performed, automatically. The physiological condition of memory is, then, the organic process by which nerve-experiences in the different centres are registered; and to recollect is to revive these experiences in the highest centres, the functions of which are attended with consciousness--to stimulate, by external or internal causes, their residua, aptitudes, dispositions, or whatever else we may choose to call them, into functional activity. Stimulated from without, they constitute recognition, that is, cognition with memory of former cognition; stimulated from within, they constitute recollection.