Historical Relations 139 



his contemporaries. Kepler sought in the events of his Hfe a 

 verification of the theory of the influence of the heavenly bodies. 

 For this purpose he kept all his life what is nothing more nor less 

 than an astrological diary. 



Kepler adopted the Copernican view from an early date, and 

 before 1595 he had turned his mind to the question of the number, 

 size, and relation of the orbits of the planets. He was ever seeking 

 a law binding the members of the solar system together. After 

 trying various simple numerical relations, after attempting to fill 

 the gaps by hypothetical planets, and after discarding various other 

 suggestions, he finally lighted on a device which satisfied him. 

 There are only five possible regular solid figures (i.e., figures with 

 equal sides and equal angles) and there are only five intervals 

 between the six planets that he recognised. As far as the calcula- 

 tions of Kepler extended at that time, the five regular solids could 

 be fitted between the spheres of the planets thus : 



Sphere of Saturn 

 Cube 



Sphere of Jupiter 

 Tetrahedron 



Sphere of Mars 

 Dodecahedron 



Sphere of Earth 

 Icosahedron 



Sphere of Venus 

 Octahedron 



Sphere of Mercury. 

 For the first time a unitafy system had been introduced in 

 explanation of the structure of the universe. We may join the 

 firm believer in revealed religion in smiling at this instance of 

 human fallibility and presumption. The basis of this unitary 

 system was miscalculation ! It endured but a day. We can smile 

 too with those who reject revealed religion at the manner in which 

 Kepler himself treated this discovery. The regular solids, he 

 observed, were of two classes, primary (cube, tetrahedron, dode- 

 cahedron) and secondary (icosahedron and octahedron) differing in 

 various ways. What more fitting than that the earth, the residence 

 of man created in God's image, be placed between the two kinds of 

 solids ! The scheme, he held, was wholly consistent with — nay, 

 was confirmatory of — many of the tenets of his religious belief. 



