The Leibnizian version of the ontological argument claims that God's existence follows from the mere possibility of a perfect being. The argument proceeds through two key steps: first establishing that if a maximally perfect being is possible, then it necessarily exists; second demonstrating that such a being involves no contradiction and is therefore possible. Unlike versions that begin with conceptual analysis or definitions, Leibniz's formulation focuses on modal logic and the coherence of divine perfections. The argument's distinctive feature is its explicit treatment of the possibility premise, which earlier versions had assumed without proof.
Gottfried Wilhelm Leibniz (1646-1716) developed this version primarily in his "Monadology" (1714) and earlier in "Meditations on Knowledge, Truth, and Ideas" (1684). His approach built upon but significantly modified Descartes's ontological argument by addressing what he saw as a crucial gap: the need to prove that the concept of God is coherent. Key defenders include Robert Maydole in "The Ontological Argument" (2009), who formalized Leibniz's intuitions using modern modal logic, and Alexander Pruss in "The Principle of Sufficient Reason" (2006). Contemporary advocates like Joshua Rasmussen in "How Reason Can Lead to God" (2019) have refined the argument using possible worlds semantics.
The strongest objection targets the possibility premise itself. Critics like J.L. Mackie in "The Miracle of Theism" (1982) argue that we cannot know whether maximal perfection is genuinely possible, as our intuitions about possibility are unreliable for such extraordinary concepts. David Hume's earlier critique in "Dialogues Concerning Natural Religion" (1779) anticipated this by questioning whether existence can be contained in any concept. Defenders respond by arguing that perfections are positive properties that cannot conflict, as Leibniz demonstrated through his theory of compossibility. They maintain that the burden of proof lies on those claiming impossibility, and that divine simplicity ensures the coherence of infinite perfections.
The Leibnizian version differs from the Anselmian argument by explicitly addressing the possibility of God rather than assuming it from conceivability. Unlike the Cartesian version, which relies on clear and distinct ideas, Leibniz provides a formal proof of possibility through perfection analysis. It contrasts with Gödel's proof by using philosophical rather than mathematical formalization, and differs from Plantinga's modal version by focusing on perfection-based possibility rather than maximal greatness across possible worlds.