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counterexample

A possible situation where an argument's premises are all true and its conclusion is false.

A counterexample to an argument is a possible situation in which every premise is true and the conclusion is false. An argument is invalid exactly when it has a counterexample. A counterexample to a form is an instance of the form with true premises and a false conclusion.

Examples

  • For "every spider has eight legs; Charlotte has eight legs; so Charlotte is a spider," a counterexample is Charlotte being a scorpion.

See also

valid invalid possible situation
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