reserve T for non empty RelStr,
  a for Element of T;

theorem
  T is reflexive & [#] T = {a} implies T is discrete
proof
  assume
A1: T is reflexive;
  set R = the InternalRel of T;
  assume
A2: [#] T = {a};
  R = id {a}
  proof
A3: id {a} = {[a,a]} by SYSREL:13;
    R c= [:{a},{a}:] by A2;
    hence R c= id {a} by A3,ZFMISC_1:29;
    let x be object;
    assume x in id {a};
    then
A4: x = [a,a] by A3,TARSKI:def 1;
    a >= a by A1,ORDERS_2:1;
    hence thesis by A4,ORDERS_2:def 5;
  end;
  hence thesis by A2;
end;
