Theorem pm2.1

Description: Theorem *2.1 of WhiteheadRussell p. 101. (Contributed by NM, 3-Jan-2005) (Proof shortened by Wolf Lammen, 23-Nov-2012)

	Ref	Expression
Assertion	pm2.1	$$⊢\left(\neg \phi \vee \phi \right)$$

Proof

Step	Hyp	Ref	Expression
1		id	$$⊢\phi \to \phi$$
2	1	imori	$$⊢\left(\neg \phi \vee \phi \right)$$