Occam's Razor

Occam's Razor (also Ockham's Razor, after the 14th-century philosopher William of Ockham) is the methodological principle that, among competing hypotheses, one should prefer the one that introduces the fewest unnecessary entities or assumptions. Commonly stated as entia non sunt multiplicanda praeter necessitatem — entities must not be multiplied beyond necessity — it is the foundational heuristic of scientific parsimony.

The principle is a heuristic, not a logical law. There is no guarantee that simpler theories are more likely to be correct. The justification for parsimony comes from Algorithmic Information Theory: the Solomonoff universal prior assigns higher probability to theories with shorter descriptions, and under a computability assumption, this assignment is asymptotically optimal. Occam's Razor is therefore a consequence of the mathematics of induction rather than an independent metaphysical principle — which means its force derives entirely from the assumption that the world has low algorithmic complexity, an assumption that cannot itself be verified without circularity.