truth-table test

Checking validity by looking for a row with true premises and a false conclusion.

The truth-table test for validity builds a table for all the premises and the conclusion and looks for a row where every premise is true and the conclusion is false. If there is none, the argument is valid; if there is one, that row is a countermodel.

Examples

For P → Q, Q ∴ P, the row P false, Q true makes both premises true and the conclusion false, so the argument is invalid.