Theorem class2set 4832

Description: Construct, from any class A, a set equal to it when the class exists and equal to the empty set when the class is proper. This theorem shows that the constructed set always exists. (Contributed by NM, 16-Oct-2003.)

Assertion

Ref	Expression
class2set	|- { x e. A | A e. _V } e. _V

Distinct variable group:   x, A

Proof of Theorem class2set

Step	Hyp	Ref	Expression
1		rabexg 4812	. 2 |- ( A e. _V -> { x e. A | A e. _V } e. _V )
2		simpl 473	. . . . 5 |- ( ( -. A e. _V /\ x e. A ) -> -. A e. _V )
3	2	nrexdv 3001	. . . 4 |- ( -. A e. _V -> -. E. x e. A A e. _V )
4		rabn0 3958	. . . . 5 |- ( { x e. A | A e. _V } =/= (/) <-> E. x e. A A e. _V )
5	4	necon1bbii 2843	. . . 4 |- ( -. E. x e. A A e. _V <-> { x e. A | A e. _V } = (/) )
6	3, 5	sylib 208	. . 3 |- ( -. A e. _V -> { x e. A | A e. _V } = (/) )
7		0ex 4790	. . 3 |- (/) e. _V
8	6, 7	syl6eqel 2709	. 2 |- ( -. A e. _V -> { x e. A | A e. _V } e. _V )
9	1, 8	pm2.61i 176	1 |- { x e. A | A e. _V } e. _V

Syntax hints:   -. wn 3   = wceq 1483   e. wcel 1990   E.wrex 2913   {crab 2916   _Vcvv 3200   (/)c0 3915

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935  ax-9 1999  ax-10 2019  ax-11 2034  ax-12 2047  ax-13 2246  ax-ext 2602  ax-sep 4781  ax-nul 4789

This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-tru 1486  df-ex 1705  df-nf 1710  df-sb 1881  df-clab 2609  df-cleq 2615  df-clel 2618  df-nfc 2753  df-ne 2795  df-ral 2917  df-rex 2918  df-rab 2921  df-v 3202  df-dif 3577  df-in 3581  df-ss 3588  df-nul 3916

This theorem is referenced by: (None)