THE BEGINNINGS OF SCIENCE 45 



tarding effect on science in later ages, for the writings 

 of these philosophers, particularly of Aristotle, were 

 the textbooks of the middle ages. 1 



Our words " theory " and " practice" are derived 

 from words introduced by them. These words were 

 used to represent two opposite ideas, and this distinc- 

 tion and separation is the real fallacy in their philosophy 

 as far as concerns natural science. We use the words 

 in essentially the same way to-day, when we are speak- 

 ing carelessly ; thus we say, " Oh, he doesn't know why 

 it works; he is just a practical man," or "He may 

 know it theoretically, but he is very impractical." 

 To the Greeks, theory was rational and pure, while 

 practice was irrational and base. One dealt with 

 celestial matters while the other dealt with terrestrial. 

 Theory was noble and practice was ignoble. This 

 latter distinction was probably due largely to the exist- 

 ence of the institution of human slavery. The me- 

 chanical tasks, like mining and later agriculture, were 

 largely performed by slave labor. This distinction 

 between noble and servile persisted even after slavery 

 had been replaced by feudalism, and persists to-day. 



It was natural that, with this differentiation in mind, 

 the Greeks, and those schoolmen of the middle ages 

 who followed their methods, should rely too much on 

 deductive reasoning, proceeding from broad and general 

 premises to determine what should be true in specific 

 cases. In the hands of the schoolmen science became 

 a matter of a priori truths, independent of experience 

 and experiment. 



1 From the decline of the Roman Empire to the Renaissance 

 (about 300 to 1400 A.D.). 



