Theorem pm3.2im 107

Description: Theorem *3.2 of [WhiteheadRussell] p. 111, expressed with primitive connectives. (The proof was shortened by Josh Purinton, 29-Dec-00.)

Assertion

Ref	Expression
pm3.2im	⊢ (φ → (ψ → ¬ (φ → ¬ ψ)))

Proof of Theorem pm3.2im

Step	Hyp	Ref	Expression
1		pm2.27 30	. 2 ⊢ (φ → ((φ → ¬ ψ) → ¬ ψ))
2	1	con2d 83	1 ⊢ (φ → (ψ → ¬ (φ → ¬ ψ)))

Syntax hints:  ¬ wn 1   → wi 2

This theorem is referenced by:  pm2.65 115  jc 119  expt 123

This theorem was proved from axioms:  ax-1 3  ax-2 4  ax-3 5  ax-mp 6

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