COMPOSITION OF CAUSES. 431 



and physiology, owe their existence to a breach of the 

 principle of Composition of Causes, it does not follow 

 that these peculiar, or as they might be termed, 

 heteropathic laws, are not capable of composition with 

 one another. The causes which by one combination 

 have had their laws altered, may carry their new laws 

 with them unaltered into their ulterior combinations. 

 And hence there is no reason to despair of ultimately 

 raising chemistry and physiology to the condition of 

 deductive sciences ; for though it is impossible to 

 deduce all chemical and physiological truths from the 

 laws or properties of simple substances or elementary 

 agents, they may probably be deducible from laws 

 which commence when these elementary agents are 

 brought together into some moderate number of not 

 very complex combinations. The Laws of Life will 

 never be deducible from the mere laws of the ingre- 

 dients, but the prodigiously complex Facts of Life may 

 all be deducible from comparatively simple laws of 

 life ; which laws, (depending indeed upon combinations, 

 but upon comparatively simple combinations, of ante- 

 cedents,) may in more complex circumstances be 

 strictly compounded with one another, and with the 

 physical and chemical laws of the ingredients. The 

 details of the vital phenomena even now afford innu- 

 merable exemplifications of the Composition of Causes ; 

 and in proportion as these phenomena are more accu- 

 rately studied, there appears more and more reason 

 to believe that the same laws which operate in the 

 simpler combinations of circumstances do, in fact, 

 continue to be observed in the more complex *. This 



* For abundant illustrations of this remark, I may refer to 

 the writings of Dr. "W. B. Carpenter, of Bristol, and especially 



