These theories, it will be observed, all assume that in perception and sensation some physical effect is produced on the system, which remains after the original sensation or perception has ceased to act, and that memory is the _result_ of that remaining effect, the perception, or conscious cognizance of it by the mind. The process is a purely physiological one. Without insisting on the expressions made use of to represent this process, all which convey the idea strongly of a mechanical effect--type imprinted on the soul, impression made on it as of a seal on wax, image, picture, copy, etc.; allowing these to be mere metaphors; allowing, moreover, that the essential fact all along assumed, is a fact, viz., that in sensation, perception, etc., some physical effect is produced on the sensorium; there are still two essential propositions to be established before we can admit any of these theories: 1. That this physical effect _remains_ any time after the cause ceases to operate; 2. That if so, it is in any way concerned in the production of memory; and even if these points could be made out, it would still be an open question, in WHAT way, possible or conceivable, this effect or impression on the sensorium gives rise to the phenomenon of memory; for this is, after all, the chief thing to be explained. CHAPTER II. IMAGINATION. § I.--GENERAL CHARACTER OF THIS FACULTY. _The Point at which we have arrived._--We have thus far treated of those forms of mental representation which are concerned in the reproduction of what has once been perceived or felt, and in the recognition of it as such. It remains still to investigate that form of the representative power, which has for its office something quite distinct from either of these, and which we may term the _creative_ faculty.