266 HISTORY OF FORMAL ASTRONOMY. 



the common theory ; and he proposes a new theory of the moon, for 

 the very reason which did at last overturn the doctrine of epicycles, 

 namely, that the ratio of their distances from the earth at different 

 times was inconsistent with the circular hypothesis. 5 



It is obvious, that, along with his mathematical clearness of view, 

 and his astronomical knowledge, Copernicus must have had great intel- 

 lectual boldness and vigor, to conceive and fully develop a theory so 

 different as his was from all received doctrines. His pupil and expos- 

 itor, Rheticus, says to Schener, "I beg you to have this opinion 

 concerning that learned man, my Preceptor ; that he was an ardent 

 admirer and follower of Ptolemy; but when he was compelled by 

 phenomena and demonstration, he thought he did well to aim at 

 the same mark at which Ptolemy had aimed, though with a bow 

 and shafts of a very different material from his. We must recollect 

 what Ptolemy says, Aet 6' ekevdepov dvai rij yvuftxi rbv \iiXkovra 

 (piXooofelv. 'He who is to follow philosophy must be a freeman in 

 mind.' " Rheticus then goes on to defend his master from the charge 

 of disrespect to the ancients : " That temper," he says, " is alien from 

 the disposition of every good man, and most especially from the spirit of 

 philosophy, and from no one more utterly than from my Preceptor. He 

 was very far from rashly rejecting the opinions of ancient philosophers, 

 except for weighty reasons and irresistible facts, through any love of 

 novelty. His years, his gravity of character, his excellent learning, his 

 magnanimity and nobleness of spirit, are very far from having any lia- 

 bility to such a temper, which belongs either to youth, or to ardent 

 and light minds, or to those r&v fiiya (pyovovvrcxiv em decdgia fJUKQ'q, 

 ' who think much of themselves and know little,' as Aristotle says." 

 Undoubtedly this deference for the great men of the past, joined with 

 the talent of seizing the spirit of their methods when the letter of their 

 theories is no longer tenable, is the true mental constitution of dis- 

 coverers. 



Besides the intellectual energy which was requisite in order to con- 

 struct a system of doctrines so novel as those of Copernicus, some 

 courage was necessary to the publication of such opinions ; certain, as 

 they were, to be met, to a great extent, by rejection and dispute, and 

 perhaps by charges of heresy and mischievous tendency. This last 

 danger, however, must not be judged so great as we might infer from 

 the angry controversies and acts of authority which occurred in Gali- 



5 De Rev. iv. c. 2. 



