# Leibniz German polymath philosopher, mathematician, and theologian (1646-1716); co-inventor of calculus (with Newton, contested); architect of the **principle of sufficient reason**; developer of the **contingency cosmological argument** in its mature form; author of the *Theodicy* (1710), which gave us the term "theodicy" itself. ## Biography - **1646**, Born in Leipzig - **1666**, Doctor of Law, University of Altdorf (refused the doctorate at Leipzig at age 20) - **1672-1676**, Diplomatic career in Paris; meets the leading philosophers of the day; develops calculus independently of Newton - **1676**, Court librarian at Hanover (lifelong post) - **1684**, Publishes calculus in *Acta Eruditorum* - **1710**, *Theodicy* (in French, *Essais de Théodicée sur la bonté de Dieu, la liberté de l'homme, et l'origine du mal*) - **1714**, *Monadology*, late metaphysical synthesis - **1716**, Died in Hanover Leibniz was multi-disciplinary at a level rarely matched: philosophy, mathematics (calculus, binary system, calculating machines), physics, geology, history, library science, jurisprudence, theology, linguistics, diplomacy. ## Major works - *Discourse on Metaphysics* (1686) - *New System of Nature* (1695) - *New Essays on Human Understanding* (written 1704; published 1765), response to Locke - *Theodicy* (1710) - *Monadology* (1714), a 90-paragraph synthesis - *Principles of Nature and of Grace* (1714) ## Major contributions ### 1. The Principle of Sufficient Reason (PSR) Leibniz's foundational metaphysical principle: > There can be found no fact that is true or existent, or any true proposition, without there being a *sufficient reason* for its being so and not otherwise, although we cannot know these reasons in most cases. (*Monadology* §32) The PSR claims: **everything that exists has a sufficient explanation for its existence**, either in something else, or in the necessity of its own nature. This is the engine of Leibniz's cosmological argument: - Every contingent thing requires explanation - The universe is contingent - The universe's explanation cannot be in itself (regress) - Therefore there must be a *necessary* being whose explanation is in itself, i.e., God See [Contingency Argument](/codex/contingency-argument/). ### 2. The contingency cosmological argument Leibniz's contingency argument is the modern-classical statement of the cosmological argument tradition. It differs from Aquinas's earlier versions ([Aquinas Five Ways](/codex/aquinas-five-ways/)) in: - Less reliance on Aristotelian act/potency metaphysics - More direct appeal to the PSR - Cleaner distinction between contingent and necessary being This argument has been revived in modern analytic philosophy of religion by: - Richard Swinburne (*The Existence of God*, 1979/2004) - [William Lane Craig](/codex/william-lane-craig/) (in cooperation with Kalam) - Alexander Pruss (*The Principle of Sufficient Reason*, 2006) - Joshua Rasmussen (*How Reason Can Lead to God*, 2019) ### 3. The "best of all possible worlds" theodicy In *Theodicy* (1710), Leibniz answers Pierre Bayle's skeptical challenge regarding evil: - God is omniscient (knows all possible worlds) - God is omnipotent (can actualize any possible world) - God is omnibenevolent (would actualize the best) - Therefore the actual world is *the best possible world* This is the most-famous version of the *best of all possible worlds* (BPW) thesis. Voltaire's *Candide* (1759) satirizes this view ruthlessly through the character Pangloss. The Leibnizian theodicy: - *Metaphysical evil* (limitation, finitude) is necessary in any created world - *Physical evil* (suffering) is permitted because it serves greater goods - *Moral evil* (sin) is permitted because the freedom that produces moral good also makes moral evil possible Leibniz's theodicy has been heavily critiqued (the actual world doesn't *seem* like the best possible) but remains a serious option in philosophy-of-religion debates. Modern Reformed treatments (Plantinga's free-will defense, see [Problem of Evil, Free Will Defense](/codex/problem-of-evil-free-will-defense/)) move away from BPW toward weaker claims (logical compatibility of God + evil), but the Leibnizian framework remains influential. ### 4. The monadology, substance metaphysics Leibniz's mature metaphysics: reality is composed of *monads*, non-extended, mind-like, simple substances. Each monad has its own complete intrinsic perceptual life; God orchestrates pre-established harmony among them. The monadology has minimal direct apologetic application but illustrates Leibniz's commitment to a deeply theistic metaphysics, every monad reflects the whole; God is the *Monad of monads* who sustains the system. ### 5. Modal metaphysics Leibniz developed sophisticated modal-logic theory: - Possible worlds as collections of co-possible states of affairs - Necessary truths = true in all possible worlds - Contingent truths = true in some but not all - God's perfect knowledge of all possible worlds (foundation for Molinism) Leibniz's modal metaphysics is foundational for: - Plantinga's modal ontological argument - Possible-worlds semantics in modern modal logic (Kripke etc.) - Molinism / middle-knowledge theology ## Leibniz on the existence of God ### Cosmological from contingency The famous question (in *Principles of Nature and Grace* §7): **"Why is there something rather than nothing?"** This question defines modern cosmological argument. Leibniz's answer: only a necessary being's existence can terminate the chain of contingent why-questions. See [Contingency Argument](/codex/contingency-argument/) and [Aquinas Five Ways](/codex/aquinas-five-ways/) (Way 3). ### Ontological argument refinement Leibniz refined Anselm's ontological argument (*New Essays* IV.10): the argument works *if* it is *possible* that a most perfect being exists. Leibniz thought the possibility could be demonstrated (no contradiction in maximal compossibility of perfections). Plantinga's modern modal version develops this insight. ## Leibniz in this corpus - [Contingency Argument](/codex/contingency-argument/), primary modern source - [Aquinas Five Ways](/codex/aquinas-five-ways/), comparison-and-development - [Modal Ontological Argument](/codex/modal-ontological-argument/), modal-metaphysics foundation - [Problem of Evil, Free Will Defense](/codex/problem-of-evil-free-will-defense/), Leibnizian-vs-Plantingan theodicy - [Free Will and Determinism](/codex/free-will-and-determinism/), Molinism foundation - [Necessary Being is an Intelligent Mind](/codex/necessary-being-is-an-intelligent-mind/) ## Reception history ### 18th-century Christian Wolff systematized Leibniz's philosophy; "Leibniz-Wolff philosophy" dominated German universities until Kant's critique. Voltaire ridiculed BPW theodicy. ### Kantian critique Kant rejected speculative metaphysics generally; Leibniz's PSR-based cosmological argument fell under Kant's critique of speculative theology. ### 20th-century revival Analytic-Christian philosophy revived Leibniz in: - Modal ontological argument (Plantinga 1974) - PSR-based cosmological argument (Pruss 2006; Rasmussen 2019) - Molinist middle-knowledge (Craig 1991) Modern Christian philosophy treats Leibniz as a major resource alongside Aquinas. ## Major secondary literature - Nicholas Jolley (ed.), *The Cambridge Companion to Leibniz* (1995) - Maria Rosa Antognazza, *Leibniz: An Intellectual Biography* (2009) - Brandon Look (ed.), *The Continuum Companion to Leibniz* (2011) - Alexander R. Pruss, *The Principle of Sufficient Reason: A Reassessment* (2006) - Robert Adams, *Leibniz: Determinist, Theist, Idealist* (1994) ## See also - [Plato](/codex/plato/), possible-worlds metaphysics has Platonic-realist heritage - [Anselm](/codex/anselm/), ontological argument origin - [Thomas Aquinas](/codex/thomas-aquinas/), cosmological argument development - [Immanuel Kant](/codex/immanuel-kant/), critique of Leibniz's speculative theology - [Alvin Plantinga](/codex/alvin-plantinga/), modern modal-metaphysics heir - [Contingency Argument](/codex/contingency-argument/) - [Aquinas Five Ways](/codex/aquinas-five-ways/) - [Modal Ontological Argument](/codex/modal-ontological-argument/) - [Problem of Evil, Free Will Defense](/codex/problem-of-evil-free-will-defense/) - Hubs Roadmap