THE MECHANISTIC CONCEPTION 25 



mechanical devices such as levers, pumps, and 

 valves, but it apparently obeys the universal law of 

 the conservation of energy. The fundamental pro- 

 cesses of oxidation in the body pass through essen- 

 tially the same stages as in the case of oxidations 

 under the control of the chemist. We may thus go 

 so far as to say that some animal processes even of 

 an elementary sort are explicable on the basis of 

 physical and chemical laws. But on the other hand, 

 we are confronted with occurrences in the animal 

 body which at least temporarily put an obstacle in 

 the way of our progress along this path. We are, 

 for example, unable to offer even a remotely satis- 

 factory solution of the directive activities which we 

 see at work. Does this situation make it necessary 

 for us, as persons honestly in pursuit of truth, to 

 give up the mechanistic hypothesis of life and 

 declare ourselves to be vitalists ? I believe we are by 

 no means in this position. The reason we are not 

 in this position is because science is progressive, 

 and while there is progress it is undeniable that 

 there is a possibility, be it ever so remote, of reaching 

 a satisfactory explanation of vital phenomena, 

 that is, an explanation in accord with recognized 

 laws of nature. The history of physical and chemical 

 discovery since Lavoisier and Faraday, and bio- 

 logical discovery since Schleider and Schwann, 

 Baer, Darwin, and Pasteur, forces us to admit that 

 the events of the nineteenth century have made a 

 revolution in men's minds. The discoveries of that 



