=Brain-scheme.=--A simple scheme will now make the whole cause of memory plain. Let _n_ be a past event, _o_ its 'setting' (concomitants, date, self present, warmth and intimacy, etc., etc., as already set forth), and _m_ some present thought or fact which may appropriately become the occasion of its recall. Let the nerve-centres, active in the thought of _m_, _n_, and _o_, be represented by _M_, _N_, and _O_, respectively; then the _existence_ of the _paths_ symbolized by the lines between _M_ and _N_ and _N_ and _O_ will be the fact indicated by the phrase 'retention of the event _n_ in the memory,' and the _excitement_ of the brain along these paths will be the condition of the event _n_'s actual recall. The _retention_ of _n_, it will be observed, is no mysterious storing up of an 'idea' in an unconscious state. It is not a fact of the mental order at all. It is a purely physical phenomenon, a morphological feature, the presence of these 'paths,' namely, in the finest recesses of the brain's tissue. The recall or recollection, on the other hand, is a _psycho-physical_ phenomenon, with both a bodily and a mental side. The bodily side is the excitement of the paths in question; the mental side is the conscious representation of the past occurrence, and the belief that we experienced it before. The only hypothesis, in short, to which the facts of inward experience give countenance is that _the brain-tracts excited by the event proper, and those excited in its recall, are in part_ DIFFERENT _from each other_. If we could revive the past event without any associates we should exclude the possibility of memory, and simply dream that we were undergoing the experience as if for the first time. Wherever, in fact, the recalled event does appear without a definite setting, it is hard to distinguish it from a mere creation of fancy. But in proportion as its image lingers and recalls associates which gradually become more definite, it grows more and more distinctly into a remembered thing. For example, I enter a friend's room and see on the wall a painting. At first I have the strange, wondering consciousness, 'Surely I have seen that before,' but when or how does not become clear. There only clings to the picture a sort of penumbra of familiarity,--when suddenly I exclaim: "I have it! It is a copy of part of one of the Fra Angelicos in the Florentine Academy--I recollect it there." Only when the image of the Academy arises does the picture become remembered, as well as seen. =The Conditions of Goodness in Memory.=--The remembered fact being _n_, then, the path N--O is what arouses for _n_ its setting when it _is_ recalled, and makes it other than a mere imagination. The path M--N, on the other hand, gives the cue or occasion of its being recalled at all. _Memory being thus altogether conditioned on brain-paths, its excellence in a given individual will depend partly on the_ NUMBER _and partly on the_ PERSISTENCE _of these paths_.