Occam's razor

Occam's razor is the principle that, among explanations fitting the evidence, the one requiring fewer assumptions should generally be preferred. It guides inquiry but does not guarantee that the simplest explanation is true.

Parsimony: A preference for explanations or models that achieve an aim with fewer assumptions or elements. Occam's razor is a rule of parsimony applied to competing explanations.
William of Ockham: A fourteenth-century English Franciscan theologian and philosopher associated with nominalism. The razor takes its name from Ockham, though the familiar wording is not securely his.
Simplicity: The quality of having few parts, assumptions, or steps. Occam's razor uses simplicity as a preference, but simplicity alone does not establish truth.
Model selection: The process of choosing among statistical or scientific models based on evidence and criteria. The razor motivates preferring a less complex model when competing models explain data comparably.
Goodman's new riddle of induction: Nelson Goodman's problem of explaining why some predicates support reliable induction while others do not. It challenges whether past success alone can tell which hypotheses deserve simpler treatment.
Bayesian inference: A framework for updating probabilities as evidence bears on competing hypotheses. Bayesian model comparison can favor simpler hypotheses by accounting for prior probabilities.
Scholasticism: A medieval intellectual tradition that used argument and commentary to reconcile authoritative texts and reason. Ockham's arguments about explanatory economy arose within scholastic debates.
Explanatory power: The extent to which an explanation accounts for observations and supports further understanding. A simpler account is preferable only when it still explains the evidence adequately.
Akaike information criterion: A statistic for selecting models that balances goodness of fit against the number of parameters. AIC formalizes a fit-complexity tradeoff, rather than applying the razor as an absolute rule.
Underdetermination: The condition in which available evidence is compatible with multiple competing theories. When evidence underdetermines theory, simplicity may guide choice without uniquely settling it.

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