Frank Ramsey on Induction: Why Validity Is the Wrong Standard

Philosopher Frank Ramsey made a subtle but important argument about how we reason. Most treatments of induction judge it by the same standard as deduction — treating it as a weaker form of logical proof. But Ramsey disagreed. His insight: induction shouldn't be judged by whether it preserves truth, like deduction does. Instead, it should be judged by whether it works — how reliably it extends our beliefs from what we've observed to what we haven't. According to this LessWrong essay, Ramsey argued that every inference has three parts: the premises, the conclusion, and the rule connecting them. For deduction, the rule guarantees truth. For induction — whether you're generalizing from patterns, reasoning by analogy, or inferring causation — the rule should be evaluated by its track record of producing true beliefs. The degree of confidence you should have in an inductive conclusion matches the proportion of cases in which that inference method tends to be right.

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