Theorem pm1.2 917

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

Assertion

Ref	Expression
pm1.2	⊢ ((𝜑 ∨ 𝜑) → 𝜑)

Proof of Theorem pm1.2

Step	Hyp	Ref	Expression
1		id 23	. 2 ⊢ (𝜑 → 𝜑)
2	1, 1	jaoi 871	1 ⊢ ((𝜑 ∨ 𝜑) → 𝜑)

This proof depends on syntax axioms:   → wi 4   ∨ wo 861

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

This proof depends on definitions:  df-bi 210  df-or 862

This theorem is used by:  oridm  918  rb-ax4  1788  sotrieq  5590  swoer  8733  pthacycspth  35891  paddidm  40866