What is Simpson's paradox?

Simpson's paradox is a concept in personal epistemology: What seems contradictory is often two statements true in different contexts.

Example: A doctor says 'exercise reduces heart disease risk.' A cardiologist says 'exercise increases risk of cardiac events.' Both are right — the first is talking about habitual moderate exercise over years, the second about vigorous exertion during a single session in someone with existing heart disease. The contradiction dissolves the moment you ask: exercise for whom, what kind, over what timeframe?

This concept is part of Phase 19 (Contradiction Resolution) in the How to Think curriculum, which builds the epistemic infrastructure for contradiction resolution.