Theorem pm1.2 900

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 22	. 2 ⊢ (𝜑 → 𝜑)
2	1, 1	jaoi 853	1 ⊢ ((𝜑 ∨ 𝜑) → 𝜑)

Syntax hints:   → wi 4   ∨ wo 843

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 209  df-or 844

This theorem is referenced by:  oridm  901  rb-ax4  1756  sotrieq  5504  swoer  8321  pthacycspth  32406  paddidm  36979