Theorem pm5.13 857

Description: Theorem *5.13 of [WhiteheadRussell] p. 123. (Contributed by NM, 3-Jan-2005.) (Proof shortened by Wolf Lammen, 14-Nov-2012.)

Assertion

Ref	Expression
pm5.13	⊢ ((φ → ψ) ∨ (ψ → φ))

Proof of Theorem pm5.13

Step	Hyp	Ref	Expression
1		pm5.14 856	1 ⊢ ((φ → ψ) ∨ (ψ → φ))

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: (None)