not how we can refuse to regard Thought as the product of Chemical change in the other; nor (in the view that all the Forces of Nature are simply expressions of Mind) do I see that we need entertain any repugnance to such a view. I do not say that it explains any Mental phenomenon. No sound Physicist would say that he can "explain" how it is that Electricity is generated by Chemical change; but he knows that such a relation of cause and effect exists between the two orders of phenomena, that every Chemical change is accompanied by an Electric disturbance; so that, whenever he witnesses Electric disturbance, he looks with assurance for some Chemical change as its Physical Cause. And in precisely the same sense, and in no other, I affirm that the Physiologist must regard some change in the Nervous substance of the Brain as the immediate Physical cause of all automatic Mental action. If this be admitted of Sensational consciousness (and how can it be denied?), we can scarcely help admitting it of Emotional; and, if of Emotional, why not of Ideational?
There is no part of our purely Physical activity, the relation of which to Physical conditions is more obvious and more intimate, than that Reproduction of past states of Consciousness; which—when supplemented by the recognition of them as having been formerly experienced—we call Memory. It is now very generally accepted by Physiologists as (to say the least) a probable doctrine, that any Idea which has once passed through the Mind, may be thus reproduced, at however long an interval, through the instrumentality of Suggestive action; the recurrence of any other state of Consciousness with which that Idea was originally linked by Association, being adequate to awaken it also from its dormant or latent condition, and to bring it within the "sphere of consciousness." And as our Ideas are thus linked in "trains" or "series," which further inosculate with each other like the branch-lines of a railway or the ramifications of an artery, so, it is considered, an Idea which has been "hidden in the obscure recesses of the mind" for years—perhaps for a lifetime—and which seems to have completely faded out of the conscious Memory (having never either recurred Automatically, or been found capable of recall by Volitional Recollection, or been recognized as a past experience when again brought before the mind), may be reproduced, as by the touching of a spring, through a nexus of Suggestions, which we can sometimes trace out continuously, but of which it does not seem necessary that all the intermediate steps should fall within our cognizance. Such a "reproduction" not unfrequently occurs when persons, revisiting certain scenes of their childhood, have found the renewal of the Sensorial impressions of places bring vividly back to their minds the remembrance of events which had occurred in connection with them; and which had not only been long forgotten by themselves, but, if narrated to them by others, would not have been recognized by them as having ever formed part of their own experience.
