Database
CLASSICAL FIRST-ORDER LOGIC WITH EQUALITY
Uniqueness and unique existence
Unique existence: the unique existential quantifier
eumoi
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exmoeub
Metamath Proof Explorer
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Theorem
eumoi
Description:
Uniqueness inferred from existential uniqueness.
(Contributed by
NM
, 5-Apr-1995)
Ref
Expression
Hypothesis
eumoi.1
⊢
∃!
x
φ
Assertion
eumoi
⊢
∃
*
x
φ
Proof
Step
Hyp
Ref
Expression
1
eumoi.1
⊢
∃!
x
φ
2
eumo
⊢
∃!
x
φ
→
∃
*
x
φ
3
1
2
ax-mp
⊢
∃
*
x
φ