reserve A for QC-alphabet;
reserve i,j,k for Nat;
reserve f for Substitution of A;
reserve x,y for bound_QC-variable of A;
reserve a for free_QC-variable of A;
reserve p,q for Element of QC-WFF(A);
reserve l,l1,l2,ll for FinSequence of QC-variables(A);
reserve r,s for Element of CQC-WFF(A);

theorem Th22:
  p is universal & bound_in p = x implies p.x = p
proof
  assume p is universal;
  then (p.x) = IFEQ(bound_in p,x,p,All(bound_in p,(the_scope_of p).x)) by Lm3;
  hence thesis by FUNCOP_1:def 8;
end;
