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Metamath Proof Explorer

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 ⊢ ∃ x φ
bnj101.2 ⊢ φ → ψ
Assertion bnj101 ⊢ ∃ x ψ

Proof

Step Hyp Ref Expression
1 bnj101.1 ⊢ ∃ x φ
2 bnj101.2 ⊢ φ → ψ
3 1 2 eximii ⊢ ∃ x ψ