Thinker · TH-0354
Richard Jeffrey
Richard Jeffrey was an American philosopher, for many years at Princeton University, who worked on decision theory, probability and logic. Standard Bayesian updating assumes…
Richard Jeffrey was an American philosopher, for many years at Princeton University, who worked on decision theory, probability and logic. Standard Bayesian updating assumes that we become certain of what we learn; Jeffrey proposed a rule for updating when experience shifts our confidence in a proposition without making it certain. Now called Jeffrey conditionalisation, it became central to formal epistemology, as did his "radical probabilism", the view that rational belief need not rest on any certain foundation.
Key ideas
- Evidence can be uncertain, so belief revision must handle shifts short of certainty.
- Jeffrey conditionalisation updates probabilities across a partition when experience changes their weights.
- Radical probabilism: there need be no bedrock of certain observation beneath rational belief.
- Decision theory can treat acts, states and outcomes alike as propositions with probabilities and desirabilities.
Major works
- The Logic of Decision (1965)
- Formal Logic: Its Scope and Limits (1967)
- Probability and the Art of Judgment (1992)
- Subjective Probability: The Real Thing (2004)
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