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Theorem con2 128
Description: Contraposition. Theorem *2.03 of [WhiteheadRussell] p. 100. (Contributed by NM, 29-Dec-1992.) (Proof shortened by Wolf Lammen, 12-Feb-2013.)
Assertion
Ref Expression
con2 ((𝜑 → ¬ 𝜓) → (𝜓 → ¬ 𝜑))

Proof of Theorem con2
StepHypRef Expression
1 id 22 . 2 ((𝜑 → ¬ 𝜓) → (𝜑 → ¬ 𝜓))
21con2d 127 1 ((𝜑 → ¬ 𝜓) → (𝜓 → ¬ 𝜑))
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem is referenced by:  con2b  347  isprm5  15205  bj-con2com  31511  bj-axtd  31544
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