theorem Th12:
  for p, Sub holds ex S st S`1 = p & S`2 = Sub
proof
  defpred P[Element of CQC-WFF(Al)] means
      for Sub holds ex S st S`1 = $1 & S`2 = Sub;
A1: for p,q,x,k for ll being CQC-variable_list of k,Al for P being
QC-pred_symbol of k,Al holds P[VERUM(Al)] & P[P!ll] &
(P[p] implies P['not' p]) & (P[p] & P[q] implies P[p '&' q]) &
(P[p] implies P[All(x,p)]) by Th1,Th2,Th4,Th5,Th11;
  thus for p holds P[p] from CQC_LANG:sch 1(A1);
end;
