Theorem pm2.54 363

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 359	. 2 |- ((ph \/ ps) <-> (-. ph -> ps))
2	1	biimpri 197	1 |- ((-. ph -> ps) -> (ph \/ ps))

This proof depends on syntax axioms:  -. wn 3   -> wi 4   \/ wo 357

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This proof depends on definitions:  df-bi 177  df-or 359

This theorem is used by:  orrd  367