Note 84 — AN ESSAY ON THE PRINCIPLES OF HUMAN ACTION TO WHICH ARE ADDED SOME REMARKS ON THE SYSTEMS OF HARTLEY AND HELVETIUS (continued 2)

I remember a story somewhere in the Arabian Nights of a man with a silver thigh. Why may not a fable serve for an illustration as well as any thing else? Metaphysics themselves are but a dry romance. Now suppose this thigh to have been endued with a power of sensation and to have answered every other purpose of a real thigh. What difference would this make in its outward appearance either to the man himself or to any one else? Or how by means of sight would he know it to be his thigh, more than it was? It would still look just like what it did, a silver thigh and nothing more. It’s impression on the eye would not depend on it’s being a sensible substance, on it’s having life in it, or being connected with the same conscious principle as the eye, but on it’s being a visible substance, that is having extension, figure, and colour.