Theorem pm2.54 389

Description: Theorem *2.54 of [WhiteheadRussell] p. 107. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
pm2.54	|- ( ( -. ph -> ps ) -> ( ph \/ ps ) )

Proof of Theorem pm2.54

Step	Hyp	Ref	Expression
1		df-or 385	. 2 |- ( ( ph \/ ps ) <-> ( -. ph -> ps ) )
2	1	biimpri 218	1 |- ( ( -. ph -> ps ) -> ( ph \/ ps ) )

Syntax hints:   -. wn 3   -> wi 4   \/ wo 383

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 197  df-or 385

This theorem is referenced by:  orrd  393  tsbi3  33942