Theorem sbcex 2994

Description: By our definition of proper substitution, it can only be true if the substituted expression is a set. (Contributed by Mario Carneiro, 13-Oct-2016.)

Assertion

Ref	Expression
sbcex	|- ( [. A / x ]. ph -> A e. _V )

Proof of Theorem sbcex

Step	Hyp	Ref	Expression
1		df-sbc 2986	. 2 |- ( [. A / x ]. ph <-> A e. { x | ph } )
2		elex 2771	. 2 |- ( A e. { x | ph } -> A e. _V )
3	1, 2	sylbi 121	1 |- ( [. A / x ]. ph -> A e. _V )

Syntax hints:   -> wi 4   e. wcel 2164   {cab 2179   _Vcvv 2760   [.wsbc 2985

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-5 1458  ax-gen 1460  ax-ie1 1504  ax-ie2 1505  ax-8 1515  ax-4 1521  ax-17 1537  ax-i9 1541  ax-ial 1545  ax-ext 2175

This theorem depends on definitions:  df-bi 117  df-sb 1774  df-clab 2180  df-cleq 2186  df-clel 2189  df-v 2762  df-sbc 2986

This theorem is referenced by:  sbcco  3007  sbc5  3009  sbcan  3028  sbcor  3030  sbcn1  3033  sbcim1  3034  sbcbi1  3035  sbcal  3037  sbcex2  3039  sbcel1v  3048  sbcel21v  3050  sbcimdv  3051  sbcrext  3063  spesbc  3071  csbprc  3492  opelopabsb  4290