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invalid

An argument is invalid if its premises could all be true while its conclusion is false.

An argument is invalid when there is at least one possible situation in which all of its premises are true and its conclusion is false. One such situation, a counterexample, is enough to show invalidity.

Examples

  • "Some cars are red. Some red things are apples. So some cars are apples." Invalid.

See also

valid counterexample
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