THE DEVELOPMENT OF THE SCIENTIFIC METHOD 79 



inner zones of the sun and planets sho^ved changes. Yet here 

 was a change in the stellar realm! In 1610, Galileo embodied 

 the early astronomical discoveries that resulted from the use 

 of the telescope in a little pamphlet, The Messenger of the 

 Heavens. In it, he described the mountains of the moon, 

 the great increase in the number of visible stars, and, above 

 all, the satellites of Jupiter, which offered a model for the 

 solar system as conceived by Copernicus. These and other 

 observations produced an attack on Galileo, especially be- 

 cause much controversy arose as to the habitability of the 

 moon, the planets, and even the stars. The idea of a plural- 

 ity of inhabited w^orlds was felt to be contrary to the Chris- 

 tian doctrines as well as to those of Aristotle. The Inquisi- 

 tion ordered Galileo to abandon his opinions and to stop 

 discussing^ them. 



Galileo turned to the philosophy of science and discussed 

 the properties of objects that are primary to the object and 

 those that depend upon the observer and are secondary to 

 the object. In this, we see the beginning of a definition of 

 the special field of science, the subject of our third chapter. 

 Then Galileo returned to his astronomical work and wrote 

 his Dialogue between the Ptolemaic and Copernican systems, 

 in which he endorsed the latter. It was received with en- 

 thusiasm by the learned but wdth wrath by the Inquisition, 

 whose edict it clearly infringed. Galileo was arrested, forced 

 to recant, and after a short period of imprisonment ordered 

 to spend the remainder of his life in seclusion, a retirement 

 that he used to the greatest advantage by further discoveries 

 in mechanics and astronomy. By the time that Galileo died, 

 in 1642, science had emerged from the medieval world, and 

 the great revolution in the thought of man was under way. 



Promoting this revolution also were two philosophers who 

 did not themselves carry out any important experimental 

 work. They were Rene Descartes and Francis Bacon. 



Descartes believed that the laws of the universe could be 

 deduced from certain simple and definite principles and that 

 these principles apply to all phenomena everywhere. The 



