Gersonides' lost commentary on the Metaphysics1

Gersonides' commentary on the Metaphysics is no longer extant and we know almost nothing about it. I shall argue that the commentary was on Averroes's long commentary and that it was not completed, perhaps not continued beyond book Γ. What made Gcrsonides, who commented so systematically on Aristotle, abandon his project, just when he was commenting on the book, that is considered by many to be the climax of Aristotle's work? The answer suggested is: Gersonides considered his astronomy as a demonstrative science. As an astronomer he developed a method, which was structurally dialectical, while the testing of the hypotheses was mainly empirical. He could reconcile his method with Aristotle's method of demonstration by a suitable interpretation of the Posterior Analytics, but not with the conception of universal science presented in Metaphysics Γ.