178 THE GREEK ASTRONOMY. 



these cases, though it does not appear that any 

 one fully succeeded before Hipparchus. 



The problem which was thus present to the 

 minds of astronomers, and which Plato is said to 

 have proposed to them in a distinct form, was, 

 " To reconcile the celestial phenomena by the com- 

 bination of equable circular motions." That the 

 circular motions should likewise be equable, was 

 a condition, which, if it had been merely tried 

 at first, as the most simple and definite conjecture, 

 would have deserved praise. But this condition, 

 which is, in reality, inconsistent with nature, was, 

 in the sequel, adhered to with a pertinacity which 

 introduced endless complexity into the system. The 

 history of this assumption is one of the most 

 marked instances of that love of simplicity and 

 symmetry, which is the source of all general truths, 

 though it so often produces and perpetuates errour. 

 At present we can easily see how fancifully the 

 notion of simplicity and perfection was interpreted, 

 in the arguments by which the opinion was de- 

 fended, that the real motions of the heavenly bodies 

 must be circular and uniform. The Pythagoreans, 

 as well as the Platonists, maintained this dogma. 

 According to Geminus, "They supposed the mo- 

 tions of the sun, and the moon, and the five planets, 

 to be circular and equable: for they would not allow 

 of such disorder among divine and eternal things, 

 as that they should sometimes move quicker, and 

 sometimes slower, and sometimes stand still; for 



