What we remember is always deficient in details compared with what we perceive. Remember a landscape, a street scene, a well-known person. Innumerable details are always lacking in the idea, although they were present in the corresponding percept. These details which are lacking may be either parts separable from the object, or mere attributes of sensation inseparable from the sensation. On the other hand, ideas are richer than percepts. They contain elements obtained from other similar perceptions and added by association, as when the idea of a landscape is enriched by a tower, the idea of a person by a beard, which actually are not present at these places. Ideas are also strongly influenced and altered by other ideas which happen to be in consciousness at the same time (“set of the mind”); for instance by questions, particularly by questions in the negative form--“did you not,” “was this not,”--by the wish to make a good impression upon others, and by similar factors. We may have no intention of exaggerating, in Falstaff’s fashion, the significance of our deeds; nevertheless our memories become gradually modified so that the uncommon, the important, the valuable in them is emphasized, and the common, the insignificant, the unpleasant is obliterated. Wherever our memories are fragmentary and indefinite, they offer but slight resistance to questions attacking this point, for instance: Do you believe that the gentleman was as tall as you are? Memories are thus, not exceptionally, but universally inaccurate representations of that which has been perceived. This has recently been proved by direct experimental tests. Since percepts, although they rest on a foundation of external stimulation, are so strongly influenced by the mind’s own manner of functioning, the existence of this influence in the case of imagery, lacking such a foundation, is not surprising. Although memories are but rarely totally misleading, mankind has long ago learned to rely upon memory in all important business and legal transactions only when there is agreement between the memories of several witnesses. The changeableness of memory is particularly strong in the child’s mind. The perceptual experiences have not been so often repeated as in the adult mind, and the practical importance of accuracy of remembering has not made itself so much felt. For both reasons the child’s memory is very unreliable. The word _imagination_ is frequently used to signify a specially strong ability to modify memories by associated images. Thus we speak of the imagination of the child--but also of the artist and the scientist. Without imagination the scientist would not succeed in his task of making the phenomena of nature more comprehensible by showing the consequences of the remotest relations between things. It is clear, however, that imagination is not a fundamental “faculty” of the mind, separable from other “faculties,” but a result of the fundamental laws governing mental functions.