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Theorem zfauscl 4519
Description: Separation Scheme (Aussonderung) using a class variable. To derive this from ax-sep 4517, we invoke the Axiom of Extensionality (indirectly via vtocl 3111), which is needed for the justification of class variable notation.

If we omit the requirement that  y not occur in  ph, we can derive a contradiction, as notzfaus 4569 shows. (Contributed by NM, 21-Jun-1993.)

Hypothesis
Ref Expression
zfauscl.1  |-  A  e. 
_V
Assertion
Ref Expression
zfauscl  |-  E. y A. x ( x  e.  y  <->  ( x  e.  A  /\  ph )
)
Distinct variable groups:    x, y, A    ph, y
Allowed substitution hint:    ph( x)

Proof of Theorem zfauscl
Dummy variable  z is distinct from all other variables.
StepHypRef Expression
1 zfauscl.1 . 2  |-  A  e. 
_V
2 eleq2 2475 . . . . . 6  |-  ( z  =  A  ->  (
x  e.  z  <->  x  e.  A ) )
32anbi1d 703 . . . . 5  |-  ( z  =  A  ->  (
( x  e.  z  /\  ph )  <->  ( x  e.  A  /\  ph )
) )
43bibi2d 316 . . . 4  |-  ( z  =  A  ->  (
( x  e.  y  <-> 
( x  e.  z  /\  ph ) )  <-> 
( x  e.  y  <-> 
( x  e.  A  /\  ph ) ) ) )
54albidv 1734 . . 3  |-  ( z  =  A  ->  ( A. x ( x  e.  y  <->  ( x  e.  z  /\  ph )
)  <->  A. x ( x  e.  y  <->  ( x  e.  A  /\  ph )
) ) )
65exbidv 1735 . 2  |-  ( z  =  A  ->  ( E. y A. x ( x  e.  y  <->  ( x  e.  z  /\  ph )
)  <->  E. y A. x
( x  e.  y  <-> 
( x  e.  A  /\  ph ) ) ) )
7 ax-sep 4517 . 2  |-  E. y A. x ( x  e.  y  <->  ( x  e.  z  /\  ph )
)
81, 6, 7vtocl 3111 1  |-  E. y A. x ( x  e.  y  <->  ( x  e.  A  /\  ph )
)
Colors of variables: wff setvar class
Syntax hints:    <-> wb 184    /\ wa 367   A.wal 1403    = wceq 1405   E.wex 1633    e. wcel 1842   _Vcvv 3059
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1639  ax-4 1652  ax-5 1725  ax-6 1771  ax-7 1814  ax-10 1861  ax-12 1878  ax-ext 2380  ax-sep 4517
This theorem depends on definitions:  df-bi 185  df-an 369  df-tru 1408  df-ex 1634  df-nf 1638  df-sb 1764  df-clab 2388  df-cleq 2394  df-clel 2397  df-v 3061
This theorem is referenced by:  inex1  4535
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