Theorem pm2.5 100

Description: Theorem *2.5 of [WhiteheadRussell] p. 107.

Assertion

Ref	Expression
pm2.5	|- (-. (ph -> ps) -> (-. ph -> ps))

Proof of Theorem pm2.5

Step	Hyp	Ref	Expression
1		pm2.21 76	. . 3 |- (-. ph -> (ph -> ps))
2	1	con3i 98	. 2 |- (-. (ph -> ps) -> -. -. ph)
3	2	pm2.21d 78	1 |- (-. (ph -> ps) -> (-. ph -> ps))

Syntax hints:  -. wn 2   -> wi 3

This theorem is referenced by:  pm5.18 658  pm5.11 660

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

Copyright terms: Public domain