a kind of force, called vital force which presides over the phenomena of living things which may be now in and now out of the matter of the living thing. Vital force as such was mostly discarded as a physiological factor a good many years ago, and in its place was put physical and chemical forces, and to-day most physiologists say that life is reducible to physical and chemical agencies; if it be true, it is not much of an answer to the question 'What is life?' for it leaves us still the question to be intelligibly answered as is the question as to the nature of heat. If one recalls how it has fared with the other queries where more knowledge has given a new and unexpected answer to each, one would be led to anticipate an answer quite different from the one somehow imagined. However it may turn out, there is evidently much work to be done and the twentieth century has the problem plainly before it.
Once more the relation of mind to body waits an answer. Is mind to be thought of as a somewhat, resident in a body, but not necessarily a part of it? If one calls it soul or spirit and thinks of it as separated from body, yet with the same attributes, capable of being now here and now there by an act of volition, unrestrained by physical factors as gravity or heat or the rest, he evidently gets the idea from his philosophy of things in which he assumes limits to the properties of matter before he has exhausted its possibilities and functions. It can not be denied that the physiological psychologists have lately been finding mind all through the bodily structure and giving an entirely different conception of soul from that usually held. However it be in reality, the problem is clearly before the twentieth century workers, and one must rest in agnosticism about it until the knowledge comes.
It seems clear that we have much to learn as to the nature of all the forms of energy, and one appears to be as mysterious as any other, though some of them, like gravitation, are so common and so constant that they awaken no curiosity in most persons and seem to be quite unrelated to personality or to philosophical and religious matters. It seems probable that whoever shall find the meaning of any of these factors will have at hand means for the disentanglement of the whole. With all these problems to be solved is there not enough for the work of the century? and whoever shall catalogue the triumphs of the twentieth century, if he can point to all these or a good part of them will have reason for holding that this century has accomplished as much and as important work as did its predecessor, the nineteenth.
