let U be Universe; ex C being U -petit Category st
( the carrier of C is not Element of U & the carrier' of C is Element of U )
reconsider m = {} as Element of U by CLASSES2:56;
consider o being set such that
A1:
not o in U
by CLASSES4:83;
set C = 1Cat (o,m);
now ( 1Cat (o,m) is U -petit & the carrier of (1Cat (o,m)) is not Element of U & the carrier' of (1Cat (o,m)) is Element of U )thus
1Cat (
o,
m) is
U -petit
by Th61;
( the carrier of (1Cat (o,m)) is not Element of U & the carrier' of (1Cat (o,m)) is Element of U )
1Cat (
o,
m)
= CatStr(#
{o},
{m},
(m :-> o),
(m :-> o),
((m,m) :-> m) #)
by CAT_1:def 11;
hence
( the
carrier of
(1Cat (o,m)) is not
Element of
U & the
carrier' of
(1Cat (o,m)) is
Element of
U )
by A1, Th18;
verum end;
hence
ex C being U -petit Category st
( the carrier of C is not Element of U & the carrier' of C is Element of U )
; verum