Moral Responsibility, although often treated from a metaphysical point of view, has seldom been regarded from a physical or physiological side, and yet it is from this source alone that we are at present able to gain any accurate information respecting the working of the mind, and it is chiefly from this basis that I purpose here regarding it. The means of observation which metaphysicians employ have been known to, and employed by, philosophers for the last two thousand years, and yet it must be admitted with but a poor result. Until physiology came to their aid, they had not arrived at a knowledge of the fact that the grey cortical matter of the brain is the seat of the mind, and that intellectual action involves definite physico-chemical changes which we are to some extent capable of estimating. The psychologists, indeed, fixing their attention solely upon subjective phenomena, resemble those fatuous fakirs, who, intent upon a particular point in their own bodies, come to believe that the umbilicus is the seat of wisdom; or, rather, they resemble the horse in a threshing floor, which, however rapidly it may seem to advance, only retraces its steps in one small unending circle. It is a simple fact that, whatever positive knowledge we possess of the mental process has been obtained by the aid of physiology, and it is equally certain that all the knowledge we are likely to attain for a long time, if not always, must be derived from the same source.