Mill, as we see, relied on his personal freedom of Will to stiffen his neck against any homage to a Power whom his moral sense declared unworthy of reverence. But a modern physiologist would tell him—and even if the fact be not fully demonstrated at present, it would, I think, be very rash for any psychologist to deny it—that by a slight change in the molecular configuration of the brain cells the heroic recusant could have been turned into a devout worshipper of any being who was able to exhibit the credentials of superior force. Such a change would certainly not be beyond the powers of a being who had heaven and hell at his disposal; even a skilful surgeon might accomplish it. What, then, is the freedom of the Will worth (it may be asked) if the direction it takes is at the mercy of the physical configuration of our brain-matter? And the ‘I’ which, we say, wills—if material changes can thus profoundly alter its character, how can we attribute to it any kind of real and independent existence? Must not the complete dispersal of the molecules of the brain at death cause the ‘I’ to vanish altogether like a blown-out flame? Must it not be at their mercy during the brief illusion of existence? Our discussion has thus plunged us into the intricate question of the relations of mind and matter, and we must pause to dwell on it for a while. What is matter? Nobody can tell. It is that which resists when we push against it—a tactile or muscular sensation. It is that of which two portions cannot occupy the same space at the same time—a visual sensation. It is the source of certain sensations; and the most recent physical investigations points to its being composed of innumerable centres of _force_. But force manifesting itself in orderly and harmonious fashion is Reason. If, then, Reason is at the base of things, Matter ceases to be a bogey. Still the fact remains that it is not I and it is not You, and the real cogency of the physiological argument against Free Will and the soul (which, as we saw, must stand or fall together) is that something done, perhaps by mere accident, to this Not-me, can, it appears, powerfully influence and change the Me in spite of all the will I can exert to the contrary. The fact that I, the innermost I, can be got at through my brain, means philosophically exactly the same as the old superstition according to which I can be got at by an enemy who sticks a waxen image of me full of pins and dissolves it before a fire. And _normally_ (there seem to me good reasons for not going further than that), _normally_, it is _only_ through Matter that the Me can be reached and influenced at all, even by the other Me’s in the universe. Now Matter, whatever else we may say about it, is certainly under the law of causation.