
theorem Th31:
  for A being non empty AltGraph, o1,o2 being Object of A st <^o1,o2^> <> {}
  for F being Covariant feasible FunctorStr over A,A st F = id A
  for m being Morphism of o1,o2 holds F.m = m
proof
  let A be non empty AltGraph, o1,o2 be Object of A such that
A1: <^o1,o2^> <> {};
  let F be Covariant feasible FunctorStr over A,A such that
A2: F = id A;
  let m be Morphism of o1,o2;
  <^F.o1,F.o2^> <> {} by A1,Def18;
  hence F.m = Morph-Map(F,o1,o2).m by A1,Def15
    .= m by A1,A2,Th30;
end;
