The famous objection to logical positivism - that its fundamental discriminatory principle was neither analytically true nor synthetically testable - can be extended to any general empiricist epistemology (any theory about how we obtain reliable knowledge about the world).

This is because any theory of this kind must also be a theory about the world - a theory that the world is the kind of place about which knowledge can be acquired in this way.

Our epistemological theories are theories about the world, and so must either be self-validating or incomplete.

Perhaps this is just another way of saying that they are subject to the open question objection, and so require recursive exposition.