Theorem spi

Description: Inference rule of universal instantiation, or universal specialization. Converse of the inference rule of (universal) generalization ax-gen . Contrary to the rule of generalization, its closed form is valid, see sp . (Contributed by NM, 5-Aug-1993)

	Ref	Expression
Hypothesis	spi.1	|- A. x ph
Assertion	spi	|- ph

Proof

Step	Hyp	Ref	Expression
1		spi.1	|- A. x ph
2		sp	|- ( A. x ph -> ph )
3	1 2	ax-mp	|- ph