"Many forms of relativism and subjectivism collapse into either self-contradiction or vacuity - self-contradiction because they end up claiming that nothing is the case, or vacuity because they boil down to the assertion that anything we say or believe is something we say or believe. I think that all general and most restricted forms of subjectivism that do not fail in either of these ways are pretty clearly false. It is usually a good strategy to ask whether a general claim about truth or meaning applies to itself. Many theories, like logical positivism, can be eliminated immediately by this test. The familiar point that relativism is self-refuting remains valid in spite of its familiarity: We cannot criticize some of our own claims of reason without employing reason at some other point to formulate and support those criticisms."
For those unfamiliar with "logical positivism," it is a philosophical position of the early-to-mid twentieth century that claimed setences were cognitively meaningless unless empirically verifiable or tautological (analytic staements, such as defintions, where the predicate is contained analytically in the subject). But by its own principle of verification the "verification principle" of logical positivism itself was cognitively meaningless, and therefore obviousyl self-contradictory. It was eventually rejected by Wittgenstein who had esposed it in his earleir work Tractatus Logico-Philosophicus.