Theorem pm2.13 911

Description: Theorem *2.13 of [WhiteheadRussell] p. 101. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
pm2.13	⊢ (𝜑 ∨ ¬ ¬ ¬ 𝜑)

Proof of Theorem pm2.13

Step	Hyp	Ref	Expression
1		notnot 143	. 2 ⊢ (¬ 𝜑 → ¬ ¬ ¬ 𝜑)
2	1	orri 876	1 ⊢ (𝜑 ∨ ¬ ¬ ¬ 𝜑)

This proof depends on syntax axioms:  ¬ wn 3   ∨ 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: (None)