24 REPORT— 1901. 



hopeless to attempt to account for the action of a principle which was 

 incomprehensible in its nature. 



For the physicist the danger is no less serious though it lies in a some- 

 what different direction. At present he is checked in his theories by the 

 necessity of making them agree with a comparatively small number of 

 fundamental hypotheses. If this check were removed his fancy might run 

 riot in the wildest speculations, which would be held to be legitimate if 

 only they led to formulae in harmony with facts. But the very habit of 

 regarding the end as everything, and the means by which it was attained 

 as unimportant, would prevent the discovery of those fragments of truth 

 which can only be uncovered by the painful process of trying to make 

 inconsistent theories agree, and using all facts, however remote, as the 

 tests of our central generalisation. 



' Science,' said Helmholtz, ' Science, whose very object it is to compre- 

 hend Nature, must start with the assumption that Nature is comprehen- 

 sible.' And again : ' The first principle of the investigator of Natui^e is to 

 assume that Nature is intelligible to us, since otherwise it would be foolish 

 to attempt the investigation at all.' These axioms do not assume that all 

 the secrets of the universe will ultimately be laid bare, but that a search 

 for them is hopeless if we undertake the quest with the conviction that it 

 will be in vain. As applied to life they do not deny that in living matter 

 something may be hidden which neither physics nor chemistry can explain, 

 but they assert that the action of physical and chemical forces in living bodies 

 can never be understood, if at every difficulty and at every check in our 

 investigations we desist from further attempts in the belief that the laws 

 of physics and chemistry have been interfered with by an incomprehensible 

 vital force. As applied to physics and chemistry they do not mean that 

 all the phenomena of life and death will ultimately be included in some 

 simple and self-sufficing mechanical theory ; they do mean that we are not 

 to sit down contented with paradoxes such as that the same thing can 

 fill both a large space and a little one ; that matter can act where it is 

 not, and the like, if by some reasonable hypothesis, capable of being 

 tested by experiment, we can avoid the acceptance of these absurdities. 

 Something will have been gained if the more obvious difficulties are 

 removed, even if we have to admit that in the background there is much 

 that we cannot grasp. 



The Limits of Physical Theories. 



And this brings me to my last point. It is a mistake to treat physical 

 theories in general, and the atomic theory in particular, as though they 

 were parts of a scheme which has failed if it leaves anything unexplained, 

 which must be carried on indefinitely on exactly the same principles, 

 whether the ultimate results are, or are not, repugnant to common sense. 



Physical theories begin at the surface with phenomena which directly 



