12 SCIENTIST 



Aristotle had tried to explain his erroneous views on 

 the speed of falling bodies by saying that it was part of 

 the essential nature of heavy bodies to fall faster than light 

 ones. In the same way he explained the development of 

 an acorn into an oak by saying it was the nature of an 

 acorn to do just that. In fact, he went somewhat further 

 than this and said that the oak was in some sense the cause 

 of the growth and development of the acorn. He carried 

 this form of reasoning into every aspect of human affairs. 

 In a particularly celebrated case, for example, he not only 

 explained but defended slavery on the grounds that it is 

 part of the essential nature of some men to serve others. 



As is well known, the church found it difficult to accept 

 the explanation of motion offered by Galileo and he was 

 subject to a series of investigations by the church authori- 

 ties. The worries that motivated these investigations were 

 similar in character to the worries that underUe the in- 

 vestigations carried out by our own Committee on Un- 

 American Activities. On the whole, the threat to the 

 medieval system of thought was more profound than are 

 most of the matters that worry our current inquisitors. 

 Nevertheless, the investigations seem to have been carried 

 out in a more thoughtful and considerate manner than those 

 that have so marred our own reputation for intellectual free- 

 dom. However that may be, the difficulty in which Galileo 

 found himself with the Pope was only in part the result of 

 differences of opinion about the speed of falling bodies and 

 whether or not the earth moves around the sun. The really 

 dangerous thing about Galileo was the way his experimental 

 approach called into question the whole method of explana- 

 tion worked out by Aristotle and elaborated by the church 

 fathers into what is known as the Natural Law. 



This basic difference in approach underlies many of 

 the discussions and outright conflicts that characterized 



