32 GENERAL PHYSIOLOGY 



ledge or knowledge of the physical world, with the aid and in 

 the sense of theoretical natural science is the reduction of 

 changes in matter to the motions of atoms, which motions are 

 accomplished by the intrinsic forces of the atoms independently 

 of time ; in other words, it is the resolution of natural events into 

 the mechanics of atoms." Recent science has, in fact, succeeded in 

 showing in gross outline how natural phenomena may be derived 

 from definite motions of atoms. We know that in all bodies the 

 atoms are moving, in gaseous bodies very actively, in liquids more 

 slowly, in solids very little. We know that light, heat and electricity 

 depend upon regular, excessively rapid vibrations of atoms ; that 

 sound is caused by definite modes of atomic vibration : and 

 that chemical changes of bodies are conditioned likewise by 

 characteristic movements and rearrangements of atoms. 



Following a fanciful conceit of Laplace, who imagines a human 

 mind perfected to the highest degree and possessing such a know- 

 ledge of atomic motions as we have in astronomy of the motions 

 of the stars, du Bois-Reymond continues : " If we were to imagine 

 all changes in the physical world to be resolved, into the motions 

 of atoms, which are due to constant intrinsic atomic forces, the 

 universe would be known in the scientific sense. The condition of 

 the world at any period of time would appear as the immediate 

 result of its condition during the previous period and the immediate 

 cause of its condition during the following period. Law and chance 

 would be merely other names for mechanical necessity. A stage 

 in the knowledge of nature can be conceived in which the whole 

 world-process would be represented by one mathematical formula, 

 by one immeasurable system of simultaneous differential equations, 

 from which could be deduced the place, direction of movement, 

 and velocity of every atom of the universe at every moment." 



The human mind is only " a feeble image," it is true, of such a 

 mind fancied by Laplace, but it differs from the latter only in 

 degree, and in the achievements of the latter we can perceive the 

 ideal which the human mind in its development is constantly ap- 

 proaching. Let us imagine for once that we had reached this 

 ideal and were in possession of the " world-formula." What would 

 then be gained ? 



In order to explain a definite phenomenon of nature, we would 

 need only to introduce into the world-formula certain values re- 

 sulting from observation, and by computation we would be able to 

 prove the phenomenon in question to be a necessary consequence 

 of our known observations. Our craving for causality would per- 

 haps be captivated for awhile by this play, but soon it would be- 

 come free again and would call to us with louder and louder voice. 

 So far so good ; we can now understand all phenomena of the 

 physical world in their causal relations to each other ; we can explain 

 them as perfectly definite motions of atoms ; but what is an atom ?' 



