Lucilio Vanini, born in 1585, was an Italian philosopher, learned in medicine, astronomy, theology, and philosophy, who, after the fashion of the scholars of the age, roamed from country to country, like the knight-errants of the days of chivalry, seeking for glory and honours, not by the sword, but by learning. This Vanini was a somewhat vain and ridiculous person. Not content with his Christian name Lucilio, he assumed the grandiloquent and high-sounding cognomen of Julius Caesar, wishing to attach to himself some of the glory of the illustrious founder of the Roman empire. As the proud Roman declared _Veni, Vidi, Vici_, so would he carry on the same victorious career, subduing all rival philosophers by the power of his eloquence and learning. He visited Naples, wandered through France, Germany, the Netherlands, Switzerland, and England, and finally stationed himself in France, first at Lyons, and then in a convent at Toulouse. At Lyons he produced his famous and fatal book, _Amphitheatrum aeternae providentiae divino-magicum Christiano-Physicum, nec non Astrologo-Catholicum_ (Lugduni, 1616). It was published with the royal assent, but afterwards brought upon its author the charge of Atheism. He concealed the poison most carefully; for apparently he defended the belief in the Divine Providence and in the immortality of the soul, but with consummate skill and subtilty he taught that which he pretended to refute, and led his readers to see the force of the arguments against the Faith of which he posed as a champion. By a weak and feeble defence, by foolish arguments and ridiculous reasoning, he secretly exposed the whole Christian religion to ridicule. But if any doubts were left whether this was done designedly or unintentionally, they were dispelled by his second work, _De admirandis naturae reginae deaeque mortalium arcanis_ (Paris, 1616), which, published in the form of sixty dialogues, contained many profane statements. In this work also he adopted his previous plan of pretending to demolish the arguments against the Faith, while he secretly sought to establish them. He says that he had wandered through Europe fighting against the Atheists wherever he met with them. He describes his disputations with them, carefully recording all their arguments; he concludes each dialogue by saying that he reduced the Atheists to silence, but with strange modesty he does not inform his readers what reasonings he used, and practically leaves the carefully drawn up atheistical arguments unanswered. The Inquisition did not approve of this subtle method of teaching Atheism, and ordered him to be confined in prison, and then to be burned alive. This sentence was carried out at Toulouse in 1619, in spite of his protestations of innocence, and the arguments which he brought forward before his judges to prove the existence of God. Some have tried to free Vanini from the charge of Atheism, but there is abundant evidence of his guilt apart from his books.