reserve A for QC-alphabet;
reserve p, q, r, s, t for Element of CQC-WFF(A);
reserve X for Subset of CQC-WFF(A);

theorem
  s => (q => p) in TAUT(A) & q in TAUT(A) & s in TAUT(A) implies p in TAUT(A)
proof
  assume s => (q => p) in TAUT(A) & q in TAUT(A);
  then s => p in TAUT(A) by Th16;
  hence thesis by CQC_THE1:46;
end;
