INDUCTION OF COPERNICUS. 265 



pursuit of symmetry and rule, and which thus produced the theory of 

 Copernicus, as they produce all theories, perpetually show their vigor 

 by overshooting their mark. They obtain something by aiming at 

 much more. They detect the order and connection which exist, by 

 imagining relations of order and connection which have no existence. 

 Real discoveries are thus mixed with baseless assumptions ; profound 

 sagacity is combined with fanciful conjecture; not rarely, or in pecu- 

 liar instances, but commonly, and in most cases; probably in all, if we 

 could read the thoughts of the discoverers as we read the books of Kep- 

 ler. To try wrong guesses is apparently the only way to hit upon 

 right ones. The character of the true philosopher is, not that he 

 never conjectures hazardously, but that his conjectures are clearly con- 

 ceived and brought into rigid contact with facts. He sees and compares 

 distinctly the ideas and the things, the relations of his notions to each 

 other and to phenomena. Under these conditions it is not only excus- 

 able, but necessary for him, to snatch at every semblance of general 

 rule ; to try all promising forms of simplicity and symmetry. 



Copernicus is not exempt from giving us, in his work, an example of 

 this character of the inventive spirit. The axiom that the celestial 

 motions must be circular and uniform, appeared to him to have strong- 

 claims to acceptation ; and his theory of the inequalities of the planet- 

 ary motions is fashioned upon it. His great desire was to apply it 

 more rigidly than Ptolemy had done. The time did not come for re- 

 jecting this axiom, till the observations of Tycho Brahe and the calcu- 

 lations of Kepler had been made. 



I shall not attempt to explain, in detail, Copernicus's system of the 

 planetary inequalities. He retained epicycles and eccentrics, altering 

 their centres of motion ; that is, he retained what was true in the old 

 system, translating it into his own. The peculiarities of his method 

 consisted in making such a combination of epicycles as to supply the 

 place of the equant* and to make all the motions equable about the 

 centres of motion. This device was admired for a time, till Kepler's 

 elliptic theory expelled it, with all other forms of the theory of epicy- 

 cles : but we must observe that Copernicus was aware of some of the 

 discrepancies which belonged to that theory as it had, up to that time, 

 been propounded. In the case of Mercury's orbit, which is more ec- 

 centric than that of the other planets, he makes suppositions which are 

 complex indeed, but which show his perception of the imperfection of 



See B. iii. Chap. iii. Sect. 7. 



