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Vacuous Truth


Vacuous truth is the truth of a conditional whose hypothesis is false. In particular, a universally quantified assertion over an empty set is vacuously true. For any predicate P, the assertion  forall x in emptyset,P(x) is true because there is no element for which P(x) is false (Morris and Morris 2025, pp. 83-84).

An empty conjunction likewise has value true, the identity element for AND. This is the logical counterpart of an empty product having value 1. By comparison, an empty disjunction has value false, corresponding to an empty sum equal to 0.


See also

AND, Conditional, Conjunction, Disjunction, Empty Product, Empty Set, Empty Sum, Universal Quantifier

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References

Morris, D. W. and Morris, J. Proofs and Concepts: The Fundamentals of Abstract Mathematics. Version 0.95, 2025. https://deductivepress.ca/dmorris/books/proofs+concepts.pdf.

Cite this as:

Weisstein, Eric W. "Vacuous Truth." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/VacuousTruth.html

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