 Al-Ghazālī studied kalām theology, Avicennian philosophy and Sufism, a type of Islamic mysticism, and he wrote about them all, as well as being one of the greatest Muslim legal theorists. Among these writings are not just The Intentions of the Philosophers, based on Avicenna’s shortest philosophical encyclopaedia (in Persian), but The Incoherence of the Philosophers, directed against falsafa as presented by Avicenna. This book was very influential, and al-Ghazālī used to be thought of as a diehard enemy of philosophy, who helped to bring about the end of philosophizing in the Islamic world. In fact, however, there are just three doctrines on which al-Ghazālī convicts Avicenna and his followers of heresy: the eternity of the world  (§3.1),  the restriction of God’s knowledge to universals and the denial of the bodily resurrection  (§3.3).  His critique thus showed that, in general, so long as these conclusions are avoided, Avicennian philosophy is acceptable for Muslims. Indeed, al-Ghazālī himself accepted it, but with two important further changes. God, he insists, has will and is capable of real choices between alternatives. Moreover—and this is the central point of the Incoherence—the philosophers such as Avicenna do not, as they claim  (§2.3),  provide demonstrative knowledge, because the starting points for their arguments are not all self-evident. Like the theologians, their reasoning is dialectical (Griffel 2009).