Now one of the principles assumed by Aristotle, and which had never been disputed, was, that if different weights of the same material were let fall from the same height, the heavier would reach the ground sooner than the lighter, and in proportion to the difference of weight. This assumption Galileo denied, and asserted that, with the exception of a small difference owing to the resistance of the air, both would fall to the ground in the same space of time. To prove his position by actual experiment, he repaired to the leaning tower of Pisa, and demonstrated that he was right and Aristotle was wrong. The Aristotelians would not believe the evidence of their own senses, and ascribed the effect to some unknown cause. To such a degree were men enslaved by authority. This provoked Galileo, and led him to attack authority with still greater vehemence, adding mockery to sarcasm; which again exasperated his opponents, and doubtless laid the foundation of that personal hostility which afterwards pursued him to the prison of the Inquisition. This blended arrogance and asperity in a young man was offensive to the whole university, yet natural to one who had overturned one of the favorite axioms of the greatest master of thought the world had seen for nearly two thousand years; and the scorn and opposition with which his discovery was received increased his rancor, so that he, in his turn, did not render justice to the learned men arrayed against him, who were not necessarily dull or obstinate because they would not at once give up the opinions in which they were educated, and which the learned world still accepted. Nor did they oppose and hate him for his new opinions, so much as from dislike of his personal arrogance and bitter sarcasms.