Theorem iotaex 4356

Description: Theorem 8.23 in [Quine] p. 58. This theorem proves the existence of the iota class under our definition. (Contributed by Andrew Salmon, 11-Jul-2011.)

Assertion

Ref	Expression
iotaex	|- (iotaxph) e. _V

Proof of Theorem iotaex

Dummy variable z is distinct from all other variables.

Step	Hyp	Ref	Expression
1		iotaval 4350	. . . . 5 |- (A.x(ph <-> x = z) -> (iotaxph) = z)
2	1	eqcomd 2358	. . . 4 |- (A.x(ph <-> x = z) -> z = (iotaxph))
3	2	eximi 1576	. . 3 |- (E.zA.x(ph <-> x = z) -> E.z z = (iotaxph))
4		df-eu 2208	. . 3 |- (E!xph <-> E.zA.x(ph <-> x = z))
5		isset 2863	. . 3 |- ((iotaxph) e. _V <-> E.z z = (iotaxph))
6	3, 4, 5	3imtr4i 257	. 2 |- (E!xph -> (iotaxph) e. _V)
7		iotanul 4354	. . 3 |- (-. E!xph -> (iotaxph) = (/))
8		0ex 4110	. . 3 |- (/) e. _V
9	7, 8	syl6eqel 2441	. 2 |- (-. E!xph -> (iotaxph) e. _V)
10	6, 9	pm2.61i 156	1 |- (iotaxph) e. _V

Syntax hints:  -. wn 3   <-> wb 176  A.wal 1540  E.wex 1541   = wceq 1642   e. wcel 1710  E!weu 2204  _Vcvv 2859  (/)c0 3550  iotacio 4337

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675  ax-6 1729  ax-7 1734  ax-11 1746  ax-12 1925  ax-ext 2334  ax-nin 4078

This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360  df-nan 1288  df-tru 1319  df-ex 1542  df-nf 1545  df-sb 1649  df-eu 2208  df-clab 2340  df-cleq 2346  df-clel 2349  df-nfc 2478  df-ne 2518  df-ral 2619  df-rex 2620  df-v 2861  df-sbc 3047  df-nin 3211  df-compl 3212  df-in 3213  df-un 3214  df-dif 3215  df-ss 3259  df-nul 3551  df-sn 3741  df-pr 3742  df-uni 3892  df-iota 4339

This theorem is referenced by:  iota4an  4358  ncfinex  4472  tfinex  4485  fvex  5339  tcex  6157