WILLIAM HARVEY, M. D. 65 



ployed by Harvey the middle term is the material cause (i. e. 

 limited quantity of fluid) , and the demonstration is " one 

 through the material cause." The major premise is a general 

 physical theorem proved by Aristotle in Books VII and VIII of 

 the Physics, where he shows that perpetual motion of any 

 system must be circular in character. The minor premise is a 

 definition of the blood derived from Harvey's careful studies 

 recorded in his earlier chapters. 



Harvey's conclusion is, as he admonishes a critic on a later 

 occasion, " demonstrative and true, and follows of necessity, 

 if the premises be true." *^ Therefore he adds that any criti- 

 cism of his conclusion cannot be in the area of argument and 

 logic, but in the area of observation and experiment which 

 supplies the premises. Harvey insists here that " our senses 

 ought to assure us whether such things be false or true and not 

 our reason, ocular testimony and not contemplation." ^^ That 

 Harvey has learned well from Aristotle, who was the father 

 both of biology and logic, is evident from Harvey's recognition 

 of and respect for the proper spheres of sense and reason. 



The degree to which Harvey's demonstration is Aristotelian 

 should be noted further. First, it is an example of the relation- 

 ship of a less general science, biology, to a more general and 

 fundamental science, physics, to which it is subalternate: a par- 

 ticular biological fact is illuminated by a universal physical 

 theorem to yield a new biological fact. Secondly, it is an ex- 

 ample of the dictum that demonstrations in science are made 

 through a definition expressing an essential characteristic. 

 Thirdly, contrary to modem thinking, Harvey's demonstration 

 does not depend on mathematical measurements but on 

 physical proportions, i. e., the proportion of one quantity to 

 another on the basis of physical comparison rather than on 

 mathematical principles. In stating that Chapter 9 is " the 

 first instance of the quantitative method in physiology " and 

 that it " introduced the most important method of reasoning in 



*^ Harvey, Second Exercise to John Riolan, ed. cit., p. 133. 



" Ibid. 



