rational actions are no more than might have been expected from the working of the mechanism of my body, would also prove that my reason is "as completely without any power to modify that working, as the steam-whistle which accompanies the work of a locomotive engine is without influence upon its machinery"? LECTURE III NATURE AND NURTURE THIS chapter, which all who have attended my lectures during the last ten years will find familiar, does not deal with the interminable question whether "acquired characters" are inherited, but, granting that this may be the case, it is an attempt to weigh the value of this "factor" in natural history. Herbert Spencer tells us that the segmentation of the backbone is the inherited effect of fractures, caused by bending, but Aristotle has shown (“Parts of Animals," I. i.) that Empedocles and the ancient writers err in teaching that the bendings to which the backbone has been subjected are the cause of its joints, since the thing to be accounted for is not the presence of joints, but the fitness of the joints for the needs of their possessor. It is an odd freak of history that we of the end of the nineteenth century are called upon to reconsider a dogma which was not only repudiated two thousand years ago, but was even then called antiquated. "Is there anything whereof it may be said: See! this is new? It hath been already of the old time which was before us." In this day of laboratories, are we not in danger of forgetting the first principle, so clearly put by Aristotle, that the thing to be explained is not the structure of organisms, but the fitness of this structure for the needs of living things in the world in which they pass their lives? We must be on our guard lest the great discovery that protoplasm is the physical basis of life obscure the truth that what Huxley has called the physical basis is one thing, while what Aristotle has called the essence of life is quite another thing. The physical basis of a locomotive engine is the expansion of steam, but its essence is fitness for the service of man. Since we accept the utility of steam-engines as a fact that does not call for explanation, we say we understand them when we have discovered that they do neither less nor more than their mechanical structure would lead us to expect. It is also clear that we might understand them, in this sense of the word, even if they grew, like animals, ready made; although it is equally clear that we should ask, in this case, how they became fitted for human needs; and that we should not admit that we understand them so long as this question is unanswered. So it is, not only with the works of man and other living things, but with the liv ing things themselves. All they do may sometime prove no more than might be expected from their physical basis; but this proof would not show why the things they do are useful to the beings that do them, or to their species. While there is nothing novel in Herbert Spencer's well-known dictum, that life is adjustment, it should help the modern reader to grasp the significance of Aristotle's teaching, to the effect that the essence of a living being is not protoplasm, but purpose. A living being is a being with properties which are useful to the possessor or to his species. If, like Paley, I kick a stone, I may change its position, raise its temperature, and bring about other changes that might all be computed from a few simple data. What happens if, instead of a stone, I kick a dog? In addition to certain changes which are obviously mechanical, like those in the stone, I start a new set of changes which could never be computed from the study of the kick alone. But note this remarkable fact: Show me the dog, and I may be able to tell you what he will do. If he have short hair, a pink skin, a big occipital crest, great cheek muscles, a long mandibular bone, a short nose with little pigment, small red eyes and crooked legs, he will not act like a dog with silky ears, curly hair, large dark eyes, a long, black pointed nose, a bushy tail, and long legs with big feet. What has the color of a dog's nose or the size of his feet to do with the effect of the kick? Obviously, nothing at all; but the changes in the dog which follow the kick are not its effect, for they might follow an unsuccessful attempt to kick precisely as |