Before proceeding further with Galileo’s researches and discoveries, so far as they fall within our province, it seems important to acquaint ourselves with his views about the Copernican system. From a letter of his to Mazzoni, of 30th May, 1597,[30] it is clear that he considered the opinions of Pythagoras and Copernicus on the position and motion of the earth to be far more correct than those of Aristotle and Ptolemy. In another letter of 4th August of the same year to Kepler, he thanks him for his work, which he had sent him, on the Mysteries of the Universe,[31] 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.”[32]