Theorem stdpc6 1679

Description: One of the two equality axioms of standard predicate calculus, called reflexivity of equality. (The other one is stdpc7 1743.) 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.)

Assertion

Ref	Expression
stdpc6	|- A. x x = x

Proof of Theorem stdpc6

Step	Hyp	Ref	Expression
1		equid 1677	. 2 |- x = x
2	1	ax-gen 1425	1 |- A. x x = x

Syntax hints:   A.wal 1329

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-gen 1425  ax-ie2 1470  ax-8 1482  ax-17 1506  ax-i9 1510

This theorem depends on definitions:  df-bi 116

This theorem is referenced by: (None)