PHILOSOPHICAL SOCIETY OF WASHINGTON. 79 



but this ancient sarcasm has now been applied to so many things 

 that it has long since lost whatever sting it may once have pos- 

 sessed, when it was fresh and new. And I also know that one of 

 the chief characteristics of true science is the sharpness with which 

 it enables us to discriminate between that which we have proven 

 and really know and that which we have not proven and do not 

 know. Better far is it, and a thousand times more in accord with 

 the simple honesty of science, to acknowledge frankly the truth that 

 phenomena occur in living beings which the inorganic forces do not 

 explain, than to mistake our wishes for discoveries, to convert con- 

 jectures into dogmas, or, worst of all, to transform an undemon- 

 strated hypothesis into a superstitious, aggressive, and intolerant 

 creed. 



Nor will the soundness of the conclusions, at which the present 

 generation shall arrive as to this matter, be without its practical 

 effect upon methods of biological research, and the consequent 

 future progress of biological science. It is not a mere metaphysi- 

 cal subtlety, but a subject of practical importance that I have asked 

 you to consider to-night. For if the chemico-physical hypothesis 

 of life be true, the only road of progress in biology lies through 

 the chemical and physical laboratories. Now, I have already this 

 evening more than once indicated how highly I esteem the class of 

 biological work that has already been done in these laboratories, 

 and I have endeavored to show how large is the unexplored biolog- 

 ical field that can be explored only in this manner. But in addi- 

 tion to all that we can ever hope to do in this direction — and I insist 

 upon its importance — I insist also upon the importance of other 

 lines of work : I insist upon the importance of the systematic 

 study of the phenomena of growth and development, of genera- 

 tion and heredity, of sensibility and mind. All that can thus 

 be learned we need to know, and not merely for its own sake. This 

 knowledge is indispensable to the right interpretation of the suc- 

 cession of life upon the globe in the past, and the successful direc. 

 tion.of the interference of the human will with the future succession 

 of life upon the globe in accordance with human necessities. We 

 shall make slow progress in this direction if we confine our efforts 

 to the application of chemistry and physics to those phenomena of 

 living beings that can be thus explained. The other phenomena, 

 not thus explicable, must also be studied in detail, arranged into 

 orderly groups, and made the basis of such inductions as our 



