Axiom ax-11 2034

Description: Axiom of Quantifier Commutation. This axiom says universal quantifiers can be swapped. Axiom scheme C6' in [Megill] p. 448 (p. 16 of the preprint). Also appears as Lemma 12 of [Monk2] p. 109 and Axiom C5-3 of [Monk2] p. 113. This axiom scheme is logically redundant (see ax11w 2007) but is used as an auxiliary axiom scheme to achieve metalogical completeness. (Contributed by NM, 12-Mar-1993.)

Assertion

Ref	Expression
ax-11	|- ( A. x A. y ph -> A. y A. x ph )

Detailed syntax breakdown of Axiom ax-11

Step	Hyp	Ref	Expression
1		wph	. . . 4 wff ph
2		vy	. . . 4 setvar y
3	1, 2	wal 1481	. . 3 wff A. y ph
4		vx	. . 3 setvar x
5	3, 4	wal 1481	. 2 wff A. x A. y ph
6	1, 4	wal 1481	. . 3 wff A. x ph
7	6, 2	wal 1481	. 2 wff A. y A. x ph
8	5, 7	wi 4	1 wff ( A. x A. y ph -> A. y A. x ph )

This axiom is referenced by:  alcoms  2035  hbal  2036  alcom  2037  hbald  2041  nfald  2165  hbae  2315  hbaltg  31713  bj-hbalt  32671  hbae-o  34188  axc711  34199  axc5c711  34203  ax12indalem  34230  ax12inda2ALT  34231  pm11.71  38597  axc5c4c711  38602  axc11next  38607  hbalg  38771  hbalgVD  39141  hbexgVD  39142