_Johann Kepler_, born of Protestant parents in Württemberg in 1571, was raised a Lutheran. In 1594 he was appointed professor of mathematics at a school in Graz, and after that he dwelt for the most time in Austria, which country became his second home. From Graz he was called to Prague to be mathematician at the imperial court, and from there to Linz to be professor at the college there. His last years were passed at Sagan and Ratisbon, where he died in 1630. Even after having left Austria he gratefully remembered the _clementia austriaca_ and the _favor archiducalis_. _Kepler’s_ astronomical achievements are known to everybody, especially his laws of the planets. With an untiring spirit of research he combined beautiful traits of character, cheerfulness, kindness, and modesty, but chiefly a profoundly religious mind. However, he was in difficult circumstances as far as his religious life was concerned. Quite early he came in conflict with the religious authorities of his confession, particularly for the reason that they considered _Kepler’s_ Copernican views as against the Bible, a fact which the learned astronomer could not see. There were also other differences. The conflict became more and more aggravated. It cannot be denied that the Lutheran Church-authorities proceeded against _Kepler_ with a lack of consideration never shown by Rome against men like _Galileo_. _Kepler_ was expelled from the Lutheran Church, and despite his efforts to be reinstated the ban was never lifted. Like _Kepler_, so was his predecessor at the Catholic court of Prague, the Danish astronomer _Tycho Brahe_ (died 1601), a devout Protestant, but the trials of _Kepler_ were spared him. His erroneous idea that the Copernican system conflicted with Holy Writ kept him from subscribing to it: it led him to devise a system midway between _Copernicus_ and _Ptolemy_. His religious sentiment is evidenced by a passage from a letter of his, written at his father’s death, “Although there are many consolations for me, of a religious nature based on Holy Writ, and of a philosophical kind drawn from the contemplation of the fate of all men and of the inconstancy of everything under the moon, it is a special comfort for me that my father departed so sweetly and piously from this valley of misery to the heavenly eternal home, where, according to _St. Paul_, we shall find a lasting abode.”