Cromwell's rule

proper noun

A rule stating that the use of prior probabilities of 0 or 1 should be avoided, except when applied to statements that are logically true or false, so as to leave room for the possibility that something very unlikely is in fact the case.

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Meanings

proper noun
  1. A rule stating that the use of prior probabilities of 0 or 1 should be avoided, except when applied to statements that are logically true or false, so as to leave room for the possibility that something very unlikely is in fact the case.

Origin

Named by statistician Dennis Lindley, in reference to Oliver Cromwell, who wrote in 1650: "I beseech you, in the bowels of Christ, think it possible that you may be mistaken."

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Cite this entry
APA

Cromwell's rule. (n.d.). In WatkinsX Dictionary. Retrieved November 4, 2026, from https://dictionary.watkinsx.com/word/Cromwell's%20rule

MLA

“Cromwell's rule.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/Cromwell's%20rule. Accessed November 4, 2026.

Chicago

WatkinsX Dictionary, s.v. “Cromwell's rule,” accessed November 4, 2026, https://dictionary.watkinsx.com/word/Cromwell's%20rule.

Source: Cromwell's rule on Wiktionary, CC BY-SA 4.0.