reserve o,m for set;
reserve C for Cartesian_category;
reserve a,b,c,d,e,s for Object of C;

theorem
  Hom(a,[1]C) = {term a}
proof
  for f2 being Morphism of a,[1]C holds term a = f2 by Th12;
  hence thesis by Th13,CAT_1:8;
end;
