theorem Th11:
  PHI \/ {p} is Consistent or PHI \/ {'not' p} is Consistent
proof
  assume not PHI \/ {p} is Consistent & not PHI \/ {'not' p} is Consistent;
  then PHI |- 'not' p & PHI |- p by HENMODEL:9,10;
  hence contradiction by HENMODEL:def 2;
end;
