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Theorem stdpc6 1702
Description: One of the two equality axioms of standard predicate calculus, called reflexivity of equality. (The other one is stdpc7 1946.) Axiom 6 of [Mendelson] p. 95. Mendelson doesn't say why he prepended the redundant quantifier, but it was probably to be compatible with free logic (which is valid in the empty domain). (Contributed by NM, 16-Feb-2005.)
Ref Expression

Proof of Theorem stdpc6
StepHypRef Expression
1 equid 1691 . 2
21ax-gen 1556 1
Colors of variables: wff set class
Syntax hints:  A.wal 1550
This theorem is referenced by:  cbv3hOLD  1981  cbv3hOLD7  29965
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1556  ax-5 1567  ax-17 1628  ax-9 1669  ax-8 1690
This theorem depends on definitions:  df-bi 179  df-ex 1552
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