TWENTIETH CENTURY SCIENCE PROBLEMS. 251 



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 phi- 

 losophy of things in which he assumes limits to the properties of mat- 

 ter 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 con- 

 stant that they awaken no curiosity in most persons and seem to be 

 quite unrelated to personality or to philosophical and religious mat- 

 ters. 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 nine- 

 teenth. 



