Database
CLASSICAL FIRST-ORDER LOGIC WITH EQUALITY
Uniqueness and unique existence
Unique existence: the unique existential quantifier
eumo
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eumoi
Metamath Proof Explorer
Ascii
Structured
Theorem
eumo
Description:
Existential uniqueness implies uniqueness.
(Contributed by
NM
, 23-Mar-1995)
Ref
Expression
Assertion
eumo
⊢
( ∃!
𝑥
𝜑
→ ∃*
𝑥
𝜑
)
Proof
Step
Hyp
Ref
Expression
1
df-eu
⊢
( ∃!
𝑥
𝜑
↔ ( ∃
𝑥
𝜑
∧ ∃*
𝑥
𝜑
) )
2
1
simprbi
⊢
( ∃!
𝑥
𝜑
→ ∃*
𝑥
𝜑
)