EXISTENCE : (thm -> thm)
STRUCTURE
SYNOPSIS
Deduces existence from unique existence.
DESCRIPTION
When applied to a theorem with a unique-existentially quantified conclusion, EXISTENCE returns the same theorem with normal existential quantification over the same variable.
    A |- ?!x. p
   -------------  EXISTENCE
    A |- ?x. p

FAILURE
Fails unless the conclusion of the theorem is unique-existentially quantified.
SEEALSO
HOL  Kananaskis-14