Alvin Plantinga
Renowned Christian epistemologist who, despite his theistic commitments, delivered one of the most influential critiques of bayesian-apologetics.
Key Contribution: Dwindling Probabilities
Plantinga critiqued richard-swinburne’s Bayesian-historical arguments by identifying the principle of dwindling probabilities: 1
A historical argument for the resurrection requires a chain of connected hypotheses:
- God exists
- God wanted to become incarnate
- Jesus was that incarnation
- The tomb was empty
- The post-mortem appearances were physical …and so on.
When you multiply the probabilities of multiple events together in probability calculus, the overall probability drastically drops. This makes it nearly impossible to arrive at a high posterior probability for complex, multi-layered historical-theological claims.
Broader Position
Plantinga is associated with reformed-epistemology — the view that belief in God can be rational without requiring strict empirical or mathematical proof. His critique of Bayesian apologetics is thus an internal one: even from a theistic standpoint, the mathematical approach is flawed.
Modal Logic and the Ontological Argument
Plantinga has also used the S5 system of modal logic in formulating a modal version of the ontological argument. S5’s reduction principle — that “possibly necessary” entails “necessary” (◇□A → □A) — is the formal backbone of his argument: if a maximally great being is possible (exists in at least one possible world), then it is necessary (exists in all possible worlds), and therefore exists actually. Plantinga has argued this feature of S5 is not counter-intuitive but follows naturally from the semantics of necessity. 2
See Also
- dwindling-probabilities
- bayesian-apologetics
- reformed-epistemology
- richard-swinburne
- s5-modal-logic
- modal-logic
- ontological-arguments
- aristotle — Aristotelian-Scholastic foundations of modal metaphysics