Just as when we enquired into the basic nature of antonyms, we carried our investigation a little below the surface of the organism, so may we here carry on a similar study to advantage. It is obvious that the readiness with which we respond to the objects called “good” is necessarily dependent upon the integrity of certain internal mechanisms, which, though never observed in their uninterrupted working, have nevertheless been deduced from a multitude of scientific investigations. Moreover, it has been discovered that every response we make is chiefly a function of the muscular and nervous systems of the body. How, indeed, would a child reach out for candy unless his arm were an extensible hinge, and how could it be extended unless something, namely, his triceps muscle, pulled on the radial bone, and how also could the muscle contract, unless a motor nerve from the spinal cord were stimulated to perform this specific activity? We do not, of course, specify that the definition of “good” be restricted to imply only this particular set of facts, but on the other hand we stipulate that this significant mechanism be not lost sight of by him who seeks without prejudice to understand how ethical concepts originate. Even more specific information than this is now available. Any muscle that is ready to contract (or, as the vitalist would say, to do Psyche’s bidding in attaining Homo’s _good_) is said to be in a condition of tonus or elastic tension. So far, then, as the muscles are concerned, the “good” of Class A implies a normal muscular tonus, which can, under the proper conditions, be developed into a full contraction. Physicians know that in both of the abnormal conditions of tetanus and contractured tonus, the organism cannot obtain some of the things which are essential for its adaptation of the world about it. The possession of a normal muscular tonus is, then, an ethical desideratum of no mean importance.