Logic / Unit 5 Logic 191 short lesson, about 20 seconds
What a Proof Is
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The idea
A proof is a sequence of statements, each a premise or derived from earlier lines by a valid rule, ending at the conclusion.
In practice
If every step is guaranteed, the destination is guaranteed. Validity, assembled by hand.
Where people slip
Tables verify; proofs construct. For arguments with many letters, proofs are also dramatically shorter.
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