PSR, Modal Collapse, and Open Future in Ibn Sīnā's Philosophy

Abstract

It has been contended that the Principle of Sufficient Reason (PSR) implies necessitarianism—that is, the view that everything occurs out of necessity. Discussing a well-known argument for this claim developed by contemporary metaphysicians, I show that Ibn Sīnā has anticipated a counterpart of this argument, and that is precisely why he is usually described as a necessitarian. This raises a puzzle because he also appears to endorse the existence of contingencies in the world. In particular, he seems to believe that the future is open, not only epistemically and alethically but also ontically. This means that there are future states of affairs that are genuinely contingent and the truth values of the propositions expressing these states are not determined now. Focusing on Ibn Sīnā's commitment to the Coexistence Principle—according to which the cause coexists with the effect—I will provide a solution to the aforementioned puzzle.