with force, actual and potential; all sensitive to the same forces in its environment and susceptible to the contagion of higher and subtler ones residing in such superior organisms as it may be brought into relation with, as those of man when he is fashioning it into an instrument of his will. It absorbs something of his intelligence and purpose—more of them in proportion to the complexity of the resulting machine and that of its work.
"Do you happen to recall Herbert Spencer's definition of 'Life'? I read it thirty years ago. He may have altered it afterward, for anything I know, but in all that time I have been unable to think of a single word that could profitably be changed or added or removed. It seems to me not only the best definition, but the only possible one.
"'Life,' he says, 'is a definite combination of heterogeneous changes, both simultaneous and successive, in correspondence with external coexistences and sequences.'"
"That defines the phenomenon," I said, "but gives no hint of its cause."
"That," he replied, "is all that any definition can do. As Mill points out, we know nothing of cause except as an antecedent—nothing of effect except as a consequent. Of
