reserve A,B,C for Ordinal,
  K,L,M,N for Cardinal,
  x,y,y1,y2,z,u for object,X,Y,Z,Z1,Z2 for set,
  n for Nat,
  f,f1,g,h for Function,
  Q,R for Relation;
reserve ff for Cardinal-Function;

theorem Th1:
  Card ff = ff
proof
  now
    let x;
    assume x in dom ff;
    then reconsider M = ff.x as Cardinal by Def1;
    card M = M;
    hence ff.x = card (ff.x);
  end;
  hence thesis by Def2;
end;
