Database
CLASSICAL FIRST-ORDER LOGIC WITH EQUALITY
Predicate calculus with equality: Auxiliary axiom schemes (4 schemes)
Axiom scheme ax-10 (Quantified Negation)
nfe1
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nfa1
Metamath Proof Explorer
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Theorem
nfe1
Description:
The setvar
x
is not free in
E. x ph
.
(Contributed by
Mario Carneiro
, 11-Aug-2016)
Ref
Expression
Assertion
nfe1
⊢
Ⅎ
x
∃
x
φ
Proof
Step
Hyp
Ref
Expression
1
hbe1
⊢
∃
x
φ
→
∀
x
∃
x
φ
2
1
nf5i
⊢
Ⅎ
x
∃
x
φ