theorem Th12:
  x, <%e%> ==>* y, <%>E, _bool TS implies x, <%e%> ==>. y, <%>E, _bool TS
proof
  not <%>E in rng dom (the Tran of _bool TS) by REWRITE3:def 1;
  hence thesis by REWRITE3:92;
end;
