Gibbard's theorem

proper noun

A theorem stating that, for any deterministic process of collective decision, at least one of the following three properties must hold: (i) the process is dictatorial, i.e. there exists a distinguished agent who can impose the outcome; (ii) the process limits the possible outcomes to two options only; (iii) the process encourages agents to think strategically: once an agent has identified their preferences, they have no action at their disposal that would best defend their opinions in any situation.

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Meanings

proper noun
  1. A theorem stating that, for any deterministic process of collective decision, at least one of the following three properties must hold: (i) the process is dictatorial, i.e. there exists a distinguished agent who can impose the outcome; (ii) the process limits the possible outcomes to two options only; (iii) the process encourages agents to think strategically: once an agent has identified their preferences, they have no action at their disposal that would best defend their opinions in any situation.

Origin

Proven by philosopher Allan Gibbard in 1973.

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Cite this entry
APA

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

MLA

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

Chicago

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

Source: Gibbard's theorem on Wiktionary, CC BY-SA 4.0.