Leibniz, God and Necessity by Michael V. Griffin (review)

In this engaging book, Griffin advances a new interpretation of Leibniz’s views on modality and their relation to natural theology. The first part of the work focuses on the necessity of God’s existence, the second on the necessity of the created world, and the third on God’s knowledge of counterfactuals and conditional future contingents. Each of these three parts contains novel insights into Leibniz’s metaphysics of modality, as well as sophisticated discussions of the modal theories of important philosophical predecessors such as Descartes, Spinoza, Molina, and Suárez.

One overarching theme of this admirably clear study is the claim that early modern theories of modality were concerned not only with whether something is necessary, but also, crucially, with the reasons that something is necessary. Griffin introduces the terms ‘intrinsically necessary’ and ‘extrinsically necessary’ to distinguish two ways in which a thing can exist necessarily: something is intrinsically necessary iff its existence follows from its essence or possibility, and something is extrinsically necessary iff its existence follows from the existence of something intrinsically necessary, but not from its own essence (4).

The first part of the book discusses both Descartes’s and Leibniz’s versions of the ontological argument. Griffin’s main innovation with respect to Leibniz’s proof is that he assigns prominent roles to two Leibnizian doctrines not typically viewed as playing a part: the principle of sufficient reason and the claim that possibles strive for existence. He contends that it is the propensity of possibles to exist—which he takes to be closely linked with the principle of sufficient reason—that explains God’s existence (50–52).

In the second part, Griffin argues that Leibniz and Spinoza were both necessitarians, that is, that they held that everything metaphysically possible is actual and that everything actual is metaphysically necessary (58). While many interpreters would agree with respect to Spinoza and the early Leibniz, Griffin goes further: he insists that Leibniz was committed to necessitarianism throughout his career (3) and that, properly understood, his many apparently anti-necessitarian statements are in fact compatible with necessitarianism. Hence, this book does not claim, as others have done, that Leibniz’s mature views ultimately entail necessitarianism even though Leibniz believed he had managed to avoid it. Rather, it aims to show that Leibniz embraced necessitarianism and never intended to suggest otherwise.

According to Griffin, Leibniz’s natural theology implies necessitarianism: because God’s existence and perfection are necessary, and because it is necessary for a perfect being to choose the best possible world, the best world exists necessarily (59, 62). Passages in which Leibniz appears to condemn necessitarianism, Griffin maintains, are in fact condemnations of the doctrine that one can explain the existence of the world without invoking God’s wisdom and goodness (65). Likewise, when Leibniz insists that creatures are contingent and not metaphysically necessary, Griffin takes him to deny merely that creatures are intrinsically necessary. Griffin’s Leibniz does take creatures to be extrinsically necessary because their existence follows from God, whose “perfect nature necessitates his choice of the best” (60). Therefore, their existence is an instance of what Griffin calls metaphysical necessity, or “the strongest form of necessity” (3). The book even effects an astonishing reconciliation of Leibniz’s insistence that there are unactualized possible worlds and necessitarianism: Leibniz’s possible, non-actual worlds are merely intrinsically possible, that is, non-self-contradictory, but they are extrinsically and metaphysically impossible because they are incompatible with God (83, 105–6).

This second part of the book makes some excellent points, in particular about incom-possibility (87–111) and the importance of wisdom and goodness. Yet, the argument that Leibniz embraced necessitarianism throughout his career is not only the book’s most controversial portion, but also, sadly, its least carefully argued one. Griffin bases his case almost exclusively on very early texts and on non-textual considerations. Even more regrettably, he mentions what most other interpreters take to be Leibniz’s attempts...