In the same way, he took up again the eternal question of the prescience of God and of human liberty, and showed that no matter what had been said it was necessary to choose: either we are free and God is not omnipotent, or God is omnipotent and we are not free. To regard as true this latter hypothesis, towards which the philosopher evidently leans, would cause God to be the author of evil and of sin. It would not be impossible for God to be the author of evil as an essential condition of good, for if evil were not to exist then there could not be good; nor would it be impossible that He should be the author, not of sin, but of the possibility of sin in order that virtue might be possible, there being no virtue where it is impossible to commit sin; but therein lies a mystery which faith alone can solve, and which Aristotle at any rate has not solved, therefore let us not place reliance on Aristotle. This disguised freethinker, for he does not appear to me to be anything else, was one of the most original thinkers of the period intermediate between the Middle Ages and Descartes. MICHAEL SERVETUS; VANINI.--Such instances of temerity were sometimes fatal to their authors. Michael Servetus, a very learned Spanish physician who perhaps discovered the circulation of the blood before Harvey, disbelieved in the Trinity and in the divinity of Jesus, and, as he was a Platonist, perceived no intermediaries between God and man save ideas. Persecuted by the Catholics, he sought refuge at Geneva, believing Calvin to be more merciful than the Inquisitors, and Calvin burned him alive. Vanini, half a century later, that is at the commencement of the seventeenth, a restless, vain, and insolent man, after a life full of sudden changes of fortune, and yet distinguished, was burnt alive at Toulouse for certain passages in his _De admirandis ... arcanis_, and for having said that he would not express his opinion on the immortality of the soul until he was old, a Jew, and a German. BRUNO; CAMPANELLA.--Giordano Bruno, an astronomer and one of the first to affirm that the sun was the centre of the world, professed, despite certain precautions, a doctrine which confused God with the world and denied or excluded creation. Giordano Bruno was arrested at Venice in 1593, kept seven years in prison, and finally burnt at Rome in 1600.