theorem
  PSI |= p implies PSI |- p
proof
  set CHI = PSI \/ {'not' p};
  assume A1: PSI |= p;
  assume not PSI |- p;
  then CHI is Consistent by HENMODEL:9;
  then ex A,J,v st J,v |= CHI by Def1;
  hence contradiction by GOEDELCP:37,A1;
end;
