The importance of Monism in thus enabling us rationally to contemplate all processes of physical causation as possibly immediate exhibitions of psychism, is difficult to overrate. For it entirely discharges all distinction between the mechanical and the mental; so that if physical science were sufficiently advanced to yield a full natural explanation of all the phenomena within human experience, mankind would be in a position to gain as complete a knowledge as is theoretically possible of the psychological character of the world-eject. Already we are able to perceive the immense significance of being able to regard any sequence of natural causation as the merely phenomenal aspect of the ontological reality--the merely outward manifestation of an inward meaning. Thus, for example, I am listening to a sonata of Beethoven's played by Madame Schumann. Helmholtz tells me all that he knows about the physics and physiology of the process, both beyond and within my brain. But I feel that, even if Helmholtz were able to tell me very much more than he can, so long as he is dealing with these objective explanations, he is at work only upon the outer skin of the whole matter. The great reality is the mind of Beethoven communicating to my mind through the complex intervention of three different brains with their neuro-muscular systems, and an endless variety of aerial vibrations proceeding from a pianoforte. The method of communication has nothing more to do with the reality communicated than have the paper and ink of this essay to do with the ideas which they serve to convey. In each case a vehicle of symbols is necessary in order that one mind should communicate with another; but in both cases this is a vehicle of _symbols_, and nothing more. Everywhere, therefore, the reality may be psychical, and the physical symbolic; everywhere matter in motion may be the outward and visible sign of an inward and spiritual grace.