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Axiom ax-c11n 2205
Description: Axiom of Quantifier Substitution. One of the equality and substitution axioms of predicate calculus with equality. Appears as Lemma L12 in [Megill] p. 445 (p. 12 of the preprint).

The original version of this axiom was ax-c11 2204 and was replaced with this shorter ax-c11n 2205 ("n" for "new") in May 2008. The old axiom is proved from this one as theorem axc11 2040. Conversely, this axiom is proved from ax-c11 2204 as theorem axc11nfromc11 2242.

This axiom was proved redundant in July 2015. See theorem axc11n 2035.

This axiom is obsolete and should no longer be used. It is proved above as theorem axc11n 2035. (Contributed by NM, 16-May-2008.) (New usage is discouraged.)

Assertion
Ref Expression
ax-c11n  |-  ( A. x  x  =  y  ->  A. y  y  =  x )

Detailed syntax breakdown of Axiom ax-c11n
StepHypRef Expression
1 vx . . . 4  setvar  x
2 vy . . . 4  setvar  y
31, 2weq 1720 . . 3  wff  x  =  y
43, 1wal 1381 . 2  wff  A. x  x  =  y
52, 1weq 1720 . . 3  wff  y  =  x
65, 2wal 1381 . 2  wff  A. y 
y  =  x
74, 6wi 4 1  wff  ( A. x  x  =  y  ->  A. y  y  =  x )
Colors of variables: wff setvar class
This axiom is referenced by:  axc11-o  2267
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