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Theorem pm3.2im 565
Description: In classical logic, this is just a restatement of pm3.2 126. In intuitionistic logic, it still holds, but is weaker than pm3.2. (Contributed by Mario Carneiro, 12-May-2015.)
Assertion
Ref Expression
pm3.2im (φ → (ψ → ¬ (φ → ¬ ψ)))

Proof of Theorem pm3.2im
StepHypRef Expression
1 pm2.27 35 . 2 (φ → ((φ → ¬ ψ) → ¬ ψ))
21con2d 554 1 (φ → (ψ → ¬ (φ → ¬ ψ)))
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wi 4
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-mp 7  ax-in1 544  ax-in2 545
This theorem is referenced by:  expi  566  jc  579  expt  582  imnan  623  dfandc  777
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