Counterfactual Hypotheses, Fictions, and the Laws of Nature: The Arguments for Contingency and Possible Worlds in Leibniz, Wolff, and Bilfinger

How can we know that our world is not the only possible one? Leibniz’s claim that this world is the best of all possible worlds obviously presupposes the modal thesis that more than one world is possible. Moreover, the possibility of alternative worlds is also the crucial premise for Leibniz’s most popular defence of contingency. Even if this commitment to possible worlds may appear unproblematic to us, Leibniz’s immediate followers felt that the pluralist assumption about possible worlds required some justification. Aim of this paper is to reconstruct Leibniz’s arguments for possible worlds and contingentism, as they are stated in the Theodicy, by taking into consideration Wolff’s and Bilfinger’s critical (albeit sympathetic) discussion. Following Bilfinger’s classification, three main arguments are explored: the argument from the conceivability of counterfactual situations, the argument from fiction, and the argument from the contingency of natural laws.