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Mirrors > Home > ILE Home > Th. List > pm2.01 | GIF version |
Description: Reductio ad absurdum. Theorem *2.01 of [WhiteheadRussell] p. 100. This is valid intuitionistically (in the terminology of Section 1.2 of [Bauer] p. 482 it is a proof of negation not a proof by contradiction); compare with pm2.18dc 749 which only holds for some propositions. (Contributed by Mario Carneiro, 12-May-2015.) |
Ref | Expression |
---|---|
pm2.01 | ⊢ ((φ → ¬ φ) → ¬ φ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ax-in1 544 | 1 ⊢ ((φ → ¬ φ) → ¬ φ) |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 → wi 4 |
This theorem was proved from axioms: ax-in1 544 |
This theorem is referenced by: pm2.01d 548 con2d 554 pm2.65i 567 pm4.8 622 |
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