Logic / Unit 4 Logic 140 short lesson, about 20 seconds
Self-Contradictions
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The idea
A self-contradiction is false on every row.
In practice
p · ~p — open and not open, same store, same moment.
Where people slip
A contradiction isn't merely false; it's false in every possible circumstance. That totality powers indirect proof.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
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