Theorem pm1.2 499

Description: Axiom *1.2 of [WhiteheadRussell] p. 96, which they call "Taut". (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
pm1.2	|- ((ph \/ ph) -> ph)

Proof of Theorem pm1.2

Step	Hyp	Ref	Expression
1		id 19	. 2 |- (ph -> ph)
2	1, 1	jaoi 368	1 |- ((ph \/ ph) -> ph)

This proof depends on syntax axioms:   -> 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:  oridm  500  rb-ax4  1520