Gersonides, or Levi ben Gershon, also known by his acronym, "RaLBaG," was a French Jewish philosopher, biblical exegete, mathematician, and astronomer. He was born at Bagnols and died at Perpignan. He was the inventor of two astronomical instruments, the Jacob's staff ("baculus") and an improved camera obscura. Gersonides' literary contributions include biblical commentaries of a philosophical and moral tone, supercommentaries to Averroes's treatises on Aristotle, and his philosophical masterwork, Milhamot Adonai (Wars of the lord). Because of his knowledge of Averroes, Gersonides was exposed to a more authentic version of Aristotle than was available to his predecessors and was thus motivated to reexamine certain problems that he felt had previously been treated inadequately or incorrectly. These problems, corresponding to the six sections of the "Wars," are (1) the nature and immortality of the soul, (2) prophecy, (3) the nature of God's knowledge, (4) divine providence, (5) miracles and the structure of...