Theorem pm2.68 399

Description: Theorem *2.68 of [WhiteheadRussell] p. 108. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
pm2.68	|- (((ph -> ps) -> ps) -> (ph \/ ps))

Proof of Theorem pm2.68

Step	Hyp	Ref	Expression
1		jarl 155	. 2 |- (((ph -> ps) -> ps) -> (-. ph -> ps))
2	1	orrd 367	1 |- (((ph -> ps) -> ps) -> (ph \/ ps))

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