to Kepler, he thanks him for his work, which he had sent him, on the Mysteries of the Universe,[1] and writes as follows about the Copernican system:—
"I count myself happy, in the search after truth, to have so great an ally as yourself, and one who is so great a friend of the truth itself. It is really pitiful that there are so few who seek truth, and who do not pursue a perverse method of philosophising. But this is not the place to mourn over the miseries of our times, but to congratulate you on your splendid discoveries in confirmation of truth. I shall read your book to the end, sure of finding much that is excellent in it. I shall do so with the more pleasure, because I have been for many years an adherent of the Copernican system, and it explains to me the causes of many of the appearances of nature which are quite unintelligible on the commonly accepted hypothesis. I have collected many arguments for the purpose of refuting the latter; but I do not venture to bring them to the light of publicity, for fear of sharing the fate of our master, Copernicus, who, although he has earned immortal fame with some, yet with very many (so great is the number of fools) has become an object of ridicule and scorn. I should certainly venture to publish my speculations if there were more people like you. But this not being the case, I refrain from such an undertaking."[2]
In an answer from Grätz, of 13th October of the same year, Kepler urgently begs him to publish his researches into the Copernican system, advising him to bring them out in Germany if he does not receive permission to do so in Italy.[3] In spite of this pressing request of his eminent friend, however, Galileo was not to be induced to bring his convictions to the light yet, a hesitation which may not appear very commendable. But if we consider the existing state of science, which condemned the Copernican system as an unheard of and fantastic hypothesis, and the religious incubus which weighed down all knowledge of nature irrespective of religious belief, and if, besides all this, we remember the entire revolution in the sphere both of religion and science involved in the reception of the Copernican system, we shall be more ready to admit that Galileo had good reason to be cautious. The Coperni-
