theorem
  E is epsilon-transitive implies (E |= the_axiom_of_power_sets iff for
  X st X in E holds E /\ bool X in E)
proof
  assume
A1: E is epsilon-transitive;
  hence E |= the_axiom_of_power_sets implies for X st X in E holds E /\ bool X
  in E by Th8;
  assume for X st X in E holds E /\ bool X in E;
  then for u holds E /\ bool u in E;
  hence thesis by A1,Th8;
end;
