theorem Th8:
  bound_in All(x,p) = x & the_scope_of All(x,p) = p
proof
  All(x,p) is universal;
  then All(x,p) = All(bound_in All(x,p), the_scope_of All(x,p)) by ZF_LANG:44;
  hence thesis by ZF_LANG:3;
end;
