reserve T, X, Y for Subset of MC-wff;
reserve p, q, r, s for Element of MC-wff;
reserve T, X, Y for Subset of MC-wff;
reserve p, q, r for Element of MC-wff;
reserve T, X, Y for Subset of MC-wff;
reserve p, q, r for Element of MC-wff;

theorem
  T is S4_theory implies S4-Taut c= T
proof
  assume
A1: T is S4_theory;
  S4-Taut c= CnS4(T) by Th90,XBOOLE_1:2;
  hence thesis by A1,Th92;
end;
