CHAPTER II 



THE INFLUENCE OF ABSTRACT THOUGHT 



GREECE: ARISTOTLE 



No sooner did the Greeks turn their attention to 

 the sciences which had originated in Egypt and 

 Babylonia than the characteristic intellectual qual- 

 ity of the Hellenic genius revealed itself. Thales 

 (640-546 B.C.), who is usually regarded as the first 

 of the Greek philosophers, was the founder of Greek 

 geometry and astronomy. He was one of the seven 

 "wise men" of Greece, and might be called the 

 Benjamin Franklin of antiquity, for he was inter- 

 ested in commerce, famous for political sagacity, and 

 honored for his disinterested love of general truth. 

 His birthplace was Miletus, a Greek city on the 

 coast of Asia Minor. There is evidence that he ac- 

 quired a knowledge of Babylonian astronomy. The 

 pursuit of commerce carried him to Egypt, and there 

 he gained a knowledge of geometry. Not only so, 

 but he was able to advance this study by general- 

 izing and formulating its truths. For the Egyptians, 

 geometry was concerned with surfaces and dimen- 

 sions, with areas and cubical contents ; for the Greek, 

 with his powers of abstraction, it became a study of 

 line and angle. For example, Thales saw that the 

 angles at the base of an isosceles triangle are equal, 

 and that when two straight lines cut one another the 

 vertically opposite angles are equal. However, after 

 having established general principles, he showed him- 



