Ockham's Razor

The methodological principle attributed to William of Ockham: do not multiply entities beyond necessity — the simpler explanation, all else being equal, is to be preferred.

Parsimony principle: of two explanations with equal predictive power, prefer the one positing fewer entities or assumptions. Ockham's application: if the phenomena can be explained without positing real universals, real species, or real relations — don't posit them. Connected to his nominalism: the razor cuts away metaphysical entities not needed to explain experience. Became a foundational heuristic in science: Newton's rules of reasoning, statistical model selection (AIC/BIC penalizes complexity), algorithmic information theory.