Theorem bnj937

Description: First-order logic and set theory. (Contributed by Jonathan Ben-Naim, 3-Jun-2011) (New usage is discouraged.)

	Ref	Expression
Hypothesis	bnj937.1	$$⊢\phi \to \exists x\psi$$
Assertion	bnj937	$$⊢\phi \to \psi$$

Proof

Step	Hyp	Ref	Expression
1		bnj937.1	$$⊢\phi \to \exists x\psi$$
2		19.9v	$$⊢\exists x\psi \leftrightarrow \psi$$
3	1 2	sylib	$$⊢\phi \to \psi$$