On 5th November, 1581, Galileo, then just seventeen, entered the University of Pisa.[13] Even here the young medical student’s independent ideas and aims made way for themselves. At that time any original ideas and philosophical views not derived from the dogmas of Aristotle were unheard of. All the theories of natural science and philosophy had hitherto been referred to theology. It had been held to be the Alpha and Omega of all human knowledge. But now the period was far advanced in which it was felt to be necessary to cast off the narrow garments fashioned by religion, though at first the will to do so exceeded the power. A stir and ferment agitated men’s minds. A period of storm and stress had begun for the study of nature and the philosophical speculation so closely connected with it. Men did not as yet possess energy and ability for direct advance, so they turned with real fanaticism to ancient learning, which, being independent, and not based on religious notions, afforded them satisfaction. Under these circumstances recurrence to the past was real progress. Unconditional surrender to the ideas of others, entire adoption of opinions, some of which were not too well verified, might suit mediocrity, but it could not suffice for the powerful mind of Galileo, who was striving to find out the truth for himself. The genius of the young student rebelled fiercely against rigid adherence to an antiquated standpoint. To the horror of the followers of Aristotle, who were quite taken aback at such unheard-of audacity, he resolutely attacked in public disputations many oracular dicta of their great master hitherto unquestioned, and this even then made him many enemies, and acquired for him the epithet of “the Wrangler.”[14] Two circumstances occur during Galileo’s student years, which, in their main features, are not without historical foundation, although in detail they bear an anecdotal impress. One, which is characteristic of Galileo’s observant eye, shows us the student of nineteen devoutly praying in the Cathedral at Pisa; but he seems to have soon wearied of this occupation, for he dreamily fixed his eye on the Maestro Possenti’s beautiful lamp, hanging from an arch, which, in order to light it more readily, had been moved out of its vertical position and then left to itself. The oscillations were at first considerable, became gradually less and less, but notwithstanding the varying distances, they were all performed in the same time, as the young medical student discovered to a nicety by feeling his pulse. The isochronism of the vibrations of the pendulum was discovered![15]