Theorem bnj101

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

	Ref	Expression
Hypotheses	bnj101.1	$$⊢\exists x\phi$$
	bnj101.2	$$⊢\phi \to \psi$$
Assertion	bnj101	$$⊢\exists x\psi$$

Proof

Step	Hyp	Ref	Expression
1		bnj101.1	$$⊢\exists x\phi$$
2		bnj101.2	$$⊢\phi \to \psi$$
3	1 2	eximii	$$⊢\exists x\psi$$