consider f being morphism of (OrdC 1) such that
A1:
( f is identity & Ob (OrdC 1) = {f} & Mor (OrdC 1) = {f} )
by Th15;
A2:
for a, b being Object of (OrdC 1)
for f1 being morphism of (OrdC 1) holds f1 is Morphism of a,b
proof
let a,
b be
Object of
(OrdC 1);
for f1 being morphism of (OrdC 1) holds f1 is Morphism of a,blet f1 be
morphism of
(OrdC 1);
f1 is Morphism of a,b
A3:
dom f1 =
f
by A1, TARSKI:def 1
.=
a
by A1, TARSKI:def 1
;
cod f1 =
f
by A1, TARSKI:def 1
.=
b
by A1, TARSKI:def 1
;
then
f1 in Hom (
a,
b)
by A3, CAT_7:20;
hence
f1 is
Morphism of
a,
b
by CAT_7:def 3;
verum
end;
reconsider a1 = f as Object of (OrdC 1) by A1;
take
a1
; CAT_8:def 7 a1 is initial
let b1 be Object of (OrdC 1); CAT_8:def 6 ( Hom (a1,b1) <> {} & ex f being Morphism of a1,b1 st
for g being Morphism of a1,b1 holds f = g )
b1 = a1
by A1, TARSKI:def 1;
hence
Hom (a1,b1) <> {}
; ex f being Morphism of a1,b1 st
for g being Morphism of a1,b1 holds f = g
reconsider f1 = f as Morphism of a1,b1 by A2;
take
f1
; for g being Morphism of a1,b1 holds f1 = g
let g be Morphism of a1,b1; f1 = g
thus
f1 = g
by A1, TARSKI:def 1; verum