Abstract

The term “principle of sufficient reason” (PSR) was coined by Leibniz, and he is often regarded as its paradigmatic proponent. But as Leibniz himself often insisted, he was by no means the first philosopher to appeal to the idea that everything must have a reason. Histories of the principle attribute versions of it to various ancient authors. A few of these studies include—or at least do not exclude—medieval philosophers; one finds the PSR in Abelard, another finds it in Aquinas. And while Leibniz retains pride of place in these histories, Spinoza is sometimes said to precede him “in appreciating the importance of the Principle and placing it at the center of his philosophical system.” In this paper, the author argues that the same should be said of the Islamic philosopher Avicenna. Writing 600 years before his early modern counterparts, Avicenna routinely and consistently appeals to the PSR in generating his metaphysical system. The paper aims first to establish that Avicenna deserves a position of prominence in histories of the PSR, and then to consider how he addresses certain challenges to the PSR, especially the threat posed by necessitarianism.