Theorem pm1.5 259

Description: Axiom *1.5 (Assoc) of [WhiteheadRussell] p. 96.

Assertion

Ref	Expression
pm1.5	|- ((ph \/ (ps \/ ch)) -> (ps \/ (ph \/ ch)))

Proof of Theorem pm1.5

Step	Hyp	Ref	Expression
1		or12 258	. 2 |- ((ph \/ (ps \/ ch)) <-> (ps \/ (ph \/ ch)))
2	1	biimp 151	1 |- ((ph \/ (ps \/ ch)) -> (ps \/ (ph \/ ch)))

Syntax hints:   -> wi 3   \/ wo 222

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

This theorem depends on definitions:  df-bi 147  df-or 224

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