Theorem mo3 2099

Description: Alternate definition of "at most one". Definition of [BellMachover] p. 460, except that definition has the side condition that y not occur in ph in place of our hypothesis. (Contributed by NM, 8-Mar-1995.)

Hypothesis

Ref	Expression
mo3.1	|- F/ y ph

Assertion

Ref	Expression
mo3	|- ( E* x ph <-> A. x A. y ( ( ph /\ [ y / x ] ph ) -> x = y ) )

Distinct variable group:   x, y

Allowed substitution hints:   ph( x, y)

Proof of Theorem mo3

Step	Hyp	Ref	Expression
1		mo3.1	. . 3 |- F/ y ph
2	1	nfri 1533	. 2 |- ( ph -> A. y ph )
3	2	mo3h 2098	1 |- ( E* x ph <-> A. x A. y ( ( ph /\ [ y / x ] ph ) -> x = y ) )

Syntax hints:   -> wi 4   /\ wa 104   <-> wb 105   A.wal 1362   F/wnf 1474   [wsb 1776   E*wmo 2046

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-io 710  ax-5 1461  ax-7 1462  ax-gen 1463  ax-ie1 1507  ax-ie2 1508  ax-8 1518  ax-10 1519  ax-11 1520  ax-i12 1521  ax-bndl 1523  ax-4 1524  ax-17 1540  ax-i9 1544  ax-ial 1548  ax-i5r 1549

This theorem depends on definitions:  df-bi 117  df-nf 1475  df-sb 1777  df-eu 2048  df-mo 2049

This theorem is referenced by:  sbmo  2104  rmo3f  2961  rmo3  3081  isarep2  5346