Theorem pm5.13 666

Description: Theorem *5.13 of [WhiteheadRussell] p. 123.

Assertion

Ref	Expression
pm5.13	|- ((ph -> ps) \/ (ps -> ph))

Proof of Theorem pm5.13

Step	Hyp	Ref	Expression
1		pm2.521 103	. 2 |- (-. (ph -> ps) -> (ps -> ph))
2	1	orri 231	1 |- ((ph -> ps) \/ (ps -> ph))

Syntax hints:   -> wi 3   \/ wo 222

This theorem is referenced by:  pm5.55 677

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7

This theorem depends on definitions:  df-bi 147  df-or 224

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