Modality in Leibniz's Philosophy:
Leibniz analyzes contingency in terms of a range of different notions: hypothetical necessity, per se contingency, infinite analysis, possible free decrees of God, and moral necessity. These have been interpreted as attempts to retreat from the neccesitarian view he adopts in his early work, but I defend the view that Leibniz's commitment to necessitarianism—the claim that all truths are necessary—is an important and unwavering feature of his system.
The core of Leibniz's modal theory is the thesis that the denial of a necessary truth is contradictory. Leibniz thinks that if we take all necessary truths into account, including the nature of God, God's understanding of essences, and his will to do what is best, then all things considered all truths are necessarily true. All truths are necessarily true because the denial of any truth contradicts some necessary feature of God. Instead of understanding Leibniz's subsequent theories of contingency as abandoning necessitarianism, I treat them as attempts to account for distinctions his interlocutors draw. Rather than eschew all talk of contingency, Leibniz offers and liberally invokes proxies for this notion.
I trace the development of Leibniz's various accounts of contingency from his early to mature work in order to illustrate that they are best understood in a necessitarian framework. I develop versions of his various accounts of contingency, including per se contingency and hypothetical necessity (Chapter 1), infinite analysis and possible free decrees of God (Chapter 2), and moral necessity (Chapter 3). The outcome of my project is a systematic treatment of Leibniz's surrogate or proxy theories of contingency within his necessitarian framework. It also establishes the character of Leibnizian possible worlds, which are key for the grounding of contingent truths in the goodness of God's will. Instead of representing all logical space, possible worlds represent alternative plans for God's world creation, and are thus constrained by metaphysical principles informed by God's nature.