Following W.V.O. Quine, I consider philosophical naturalism to be a continuation of the empiricist tradition in philosophy. According to this view, all truths, including truths in philosophy, are in principle revisable in the light of new evidence. There is no room for "eternal truths" in philosophy, not even in the domain of ontology or metaphysics. An important agenda of philosophical naturalism is therefore to show why attempts to prove some eternal truth in philosophy are futile.