Theorem notnoti

Description: Inference associated with notnot . (Contributed by NM, 27-Feb-2008)

	Ref	Expression
Hypothesis	notnoti.1	$$⊢\phi$$
Assertion	notnoti	$$⊢\neg \neg \phi$$

Proof

Step	Hyp	Ref	Expression
1		notnoti.1	$$⊢\phi$$
2		notnot	$$⊢\phi \to \neg \neg \phi$$
3	1 2	ax-mp	$$⊢\neg \neg \phi$$