Letters to Kepler on the Copernicum System and the Telescope

Galileo Galilei

TO KEPLER

"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 conformation 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."

ON THE TELESCOPE

"You must know that about two months ago a report was spread here that in Flanders a spy-glass had been presented to Prince Maurice, so ingeniously constructed that it made the most distant objects appear quite near, so that a man could be seen quite plainly at a distance of two miglia. This result seemed to me so extraordinary that it set me thinking; and as it appeared to me that it depended upon the theory of perspective, I reflected on the manner of constructing it, in which I was at length so entirely successful that I made a spy-glass which far surpasses the report of the Flanders one. As the news had reached Venice that I had made such an instrument, six days ago I was summoned before their highnesses the signoria, and exhibited it to them, to the astonishment of the whole senate. Many noblemen and senators, although of a great age, mounted the steps of the highest church towers at Venice, in order to see sails and shipping that were so far [p.293] off that it was two hours before they were seen steering full sail into the harbor without my spy-glass, for the effect of my instrument is such that it makes an object fifty miglia off appear as large and near as if it were only five."

TO KEPLER

"You are the first and almost the only person who, even after but a cursory investigation, has, such is your openness of mind and lofty genius, given entire credit to my statements . . . We will not trouble ourselves about the abuses of the multitude, for against Jupiter even giants, to say nothing of pigmies, fight in vain. Let Jupiter stand in the heavens, and let the sycophants bark at him as they will. In Pisa, Florence, Bologna, Venice, and Padua many have seen the planets; but all are silent on the subject and undecided, for the greater number recognize neither Jupiter nor Mars and scarcely the moon as planets. At Venice one man spoke against me, boasting that he knew for certain that my satellites of Jupiter, which he had several times observed, were not planets because they were always to be seen with Jupiter, and either all or some of them now followed and now preceded him. What is to be done? Shall we decide with Democritus or Heraclitus? I think, my Kepler, we will laugh at the extraordinary stupidity of the multitude. What do you say to the leading philosophers of the faculty here, to whom I have offered a thousand times of my own accord to show my studies, but who with the lazy obstinacy of a serpent who has eaten his fill have never consented to look at planets, nor moon, nor telescope? Verily, just as serpents close their ears, so do these men close their eyes to the light of the truth. These are great matters; yet they do not occasion me any surprise. People of this sort think that philosophy is a kind of book like the aeneid or the Odyssey, and that the truth is to be sought, not in the universe, nor in nature, but (I use their own words) by comparing texts! How you would laugh if you heard the things the first philosopher of the faculty at Pisa brought against me in the presence of the Grand Duke, for he tried, now with logical arguments, now with magical adjurations, to tear down and to argue the new planets out of heaven."