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CLASSICAL FIRST-ORDER LOGIC WITH EQUALITY
Predicate calculus with equality: Tarski's system S2 (1 rule, 6 schemes)
Axiom scheme ax-4 (Quantified Implication)
19.35ri
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19.25
Metamath Proof Explorer
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Theorem
19.35ri
Description:
Inference associated with
19.35
.
(Contributed by
NM
, 12-Mar-1993)
Ref
Expression
Hypothesis
19.35ri.1
⊢
∀
x
φ
→
∃
x
ψ
Assertion
19.35ri
⊢
∃
x
φ
→
ψ
Proof
Step
Hyp
Ref
Expression
1
19.35ri.1
⊢
∀
x
φ
→
∃
x
ψ
2
19.35
⊢
∃
x
φ
→
ψ
↔
∀
x
φ
→
∃
x
ψ
3
1
2
mpbir
⊢
∃
x
φ
→
ψ