190 A MODEL OF NATURE. 



to be legitimate if only they led to formulae in harmony with facts. 

 Bui the verv 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 b} r the pain- 

 ful process of trying to make inconsistent theories agree, and using 

 all facts, however remote, as the tests of our central generalization. 



••Science.'" said Helmholtz, ••Science, whose very object it is to 

 comprehend Nature, must start with the assumption that Nature is 

 comprehensible." And again, "The first principle of the investigator 

 of Nature 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, hut that a search for them is hopeless if Ave 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; hut they assert that the 

 action of physical and chemical forces in living bodies can never be 

 understood if at every difficulty and at wi^vy check in our investiga- 

 tions we desist from further attempts in the belief that the laws of 

 plrysies and chemistry have been interfered with by an incomprehen- 

 sible vital force. As applied to physics and chemistry the} T 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 -it down contented with paradoxes such as 

 that the -Mine 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 can not grasp. 



THE LIMITS OF PHYSICAL THEORIES. 



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

 ical 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 he 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 

 affect our senses. When they are used in tin 1 attempt to penetrate 

 deeper into the secrets of nature, it is more than probable that they 

 will meet with insuperable barriers; but this fact does not demonstrate 

 that the fundamental assumptions are false, and the question as to 

 whether any particular obstacle will he forever insuperable- can rarely 

 be answered with certainty. 



Those who belittle the idea- which have of late governed the advance 



