22 THE HISTORY OF SCIENCE 



involves the right use of the senses as well as the 

 right use of reason. The advance of science depends 

 on the development both of speculation and observa- 

 tion. Aristotle advised investigators to make sure of 

 the facts before seeking the explanation of the facts. 

 Where preconceived theory was at variance with ob- 

 served facts, the former must of course give way. 

 Though it has been said that while Plato was a 

 dreamer, Aristotle was a thinker, yet it must be ac- 

 knowledged in qualification that Plato often showed 

 genuine knowledge of natural phenomena in anatomy 

 and other departments of study, and that Aristotle 

 was carried away at times by his own presuppositions, 

 or failed to bring his theories to the test of observa- 

 tion. The Stagirite held that the velocity of falling 

 bodies is proportional to their weight, that the func- 

 tion of the diaphragm is to divide the region of the 

 nobler from that of the animal passions, and that the 

 brain is intended to act in opposition to the heart, 

 the brain being formed of earthy and watery mate- 

 rial, which brings about a cooling effect. The theory 

 of the four elements the hot, the cold, the moist, 

 the dry led to dogmatic statements with little at- 

 tempt at verification. From the standpoint of modern 

 studies it is easy to point out the mistakes of Aris- 

 totle even. Science is progressive, not infallible. 



In his own time he was rather reproached for what 

 was considered an undignified and sordid familiarity 

 with observed facts. His critics said that having 

 squandered his patrimony, he had served in the army, 

 and, failing there, had become a seller of drugs. His 

 observations on the effects of heat seem to have been 

 drawn from the common processes of the home and 



