Logic / Unit 4 Logic 147 short lesson, about 20 seconds
The Short Truth-Table Method
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The idea
Assume the argument invalid — premises true, conclusion false — and push the forced values through. Contradiction: valid. A consistent assignment: invalid, with the counterexample row in hand.
In practice
One row of reasoning replaces sixty-four.
Where people slip
The method needs care where values aren't forced. When choices appear, all must fail before "valid" is earned.
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