42 GREAT MEN OF SCIENCE 



an almanack each year, with prophecies of the weather 

 and of political events. Astrology of this kind had unfor- 

 tunately to be Kepler's main source of income to the end of 

 his life. He calls it 'the foolish and disreputable daughter 

 of astronomy, without which the wise old mother would 

 starve. '1 



In the Graz period we have Kepler's first attempts, never 

 afterwards abandoned, to discover regularities in the planet- 

 ary system. At Graz, also, he founded a family; but quiet 

 happiness was not to be his lot. The persecution of Protest- 

 ants, which soon commenced, destroyed all security of 

 property; and finally, all those serving the Protestant 

 Churches and Schools were banished from the land, as a 

 Hapsburg (Grand Duke Ferdinand) educated by the Jesuits 

 came to the throne, Kepler was the only one allowed to 

 return. His rare gifts were highly valued; but it soon 

 appeared that he was expected to enter the Roman Church. 

 Since his conscience would not allow him to do this, and since 

 he frequently and openly made the fact known, all kinds of 

 disciplinary measures began. In this time of oppression, 

 two of his children had died; about the year 1600, threats 

 of imprisonment and torture were made. An invitation 

 by Tycho Brahe at last gave him the desired opportunity of 

 leaving Graz, which had become unbearable for him. At 

 that time, Tycho had just moved to Prague, and Kepler 

 became his assistant there, and after his early death, his 



^ In a special essay ('Warnung,' to be found in the 1858 edition of his 

 collected works, vol. I, page 547) Kepler defends himself with great seri- 

 ousness from misinterpretation of the attention he gave to this 'bastard 

 of science,' and warns against confusing 'star-gazing superstition' with 

 highly intelligent astronomy.' And on another occasion (in a letter, ib. 

 vol. 8, page 8i i) he says: 'Just as if the works of God were otherwise not 

 worthy to be looked upon and to form the subject of our calculations, 

 they are supposed to have some kind of meaning directed to such silly 

 people of peculiar disposition.' Nevertheless, his firm adherence to a 

 connection between the worlds of spirit and matter (a connection still un- 

 discovered), and therefore a connection between human fate and the 

 motion of the heavenly bodies, rendered even this work less difficult. 

 We may compare on this point the fourth book of his Hartnonices Mundi. 



