pm2.13 - Metamath Proof Explorer

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Theorem pm2.13 894

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 142	. 2 ⊢ (¬ 𝜑 → ¬ ¬ ¬ 𝜑)
2	1	orri 858	1 ⊢ (𝜑 ∨ ¬ ¬ ¬ 𝜑)

Colors of variables: wff setvar class

Syntax hints: ¬ wn 3 ∨ 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 206 df-or 844

This theorem is referenced by: (None)