Avicenna, "the Prince of Physicians," was born about 980 A.D. in Bokhara. In learning he was precocious, and during most of his somewhat stormy life he acted as physician to various emirs. He died at Hamadan A.D. 1037. His chief work, The Canon of Medicine, based upon Galen, modified by Aristotle, was a text-book in Europe until the middle of the seventeenth century. Upwards of 100 treatises are ascribed to him, dealing with the entire circle of the sciences, as then understood, from an Aristotelian standpoint. He maintains the immortality of individual souls with Platonist arguments, his theology being largely Neo-Platonist in origin.