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Theorem pm2.68 399
Description: Theorem *2.68 of [WhiteheadRussell] p. 108. (Contributed by NM, 3-Jan-2005.)
Assertion
Ref Expression
pm2.68 (((φψ) → ψ) → (φ ψ))

Proof of Theorem pm2.68
StepHypRef Expression
1 jarl 155 . 2 (((φψ) → ψ) → (¬ φψ))
21orrd 367 1 (((φψ) → ψ) → (φ ψ))
Colors of variables: wff setvar class
Syntax hints:  wi 4   wo 357
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8
This theorem depends on definitions:  df-bi 177  df-or 359
This theorem is referenced by:  dfor2  400
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