One of the most famous instances of this form of critique killing a philosophical position involves the Verification Theory of Meaning. Roughly, the VTM is
If a sentence can’t be proven true or false through empirical observation or by definition of its terms, it is meaningless.But of course the VTM itself can’t be proven true or false through empirical observation or by definition of its terms. By its own standards, it’s meaningless. That tells us that this is not a good theory of meaning. (Logically: if P implies not-P, then not-P.) It does not tell us what a good theory would be.
Epistemological skepticism is a ripe field for this kind of argument. The (naïve) skeptic says,
No one has any knowledgeand then immediately has to answer the sly question, How do you know?
Or the skeptic may say
All human thought is weak, biased, and ultimately unprovable; therefore no inferences are sound.So I guess that one isn’t sound either? Some skepticism amounts to declarations like
I have an excellent argument that no arguments are excellent! Orwhich is hard to take seriously. Such observations tell us that these skeptical positions aren’t correct. But they get us no closer to actually having any particular knowledge.
My philosophical view is that no philosophical views should be taken seriously
Hard-core historicism has a similar problem. The hard-core historicist tells us
All philosophical positions are purely products of their time and circumstances,and therefore none has a greater claim on truth than any other.But since the HCH includes himself here, his views have no special claim on truth, and we ought not pay him any more attention than we do some long-forgotten two-bit sage. You can get the same effect in logic:
Every generalization has exceptions.Each of these defeats itself. Richard Rorty is famous for his remark,
No sentence of seven words is true.
All dogmatic assertions should be rejected.
Truth is what your peers will let you get away with sayingbut his peers did not let him get away with saying this.
Morality offers similar pitfalls, often where skepticism or relativism are concerned. Suppose a cultural relativist offers
Moral principles are only valid for cultures that endorse them.What is the status of this principle outside a relativist culture? Is the relativist trying to make an (inconsistently) absolute claim, one that applies everywhere? Or are they simply trying to legislate for their own culture, and everyone else has genuinely absolute principles (which, being absolute, also apply to the relativist)? Neither option is attractive. Consider also
Moral principles are never absolute.Except this one?
No one has the right to say what morality is for everyone.
Except you, Mr. Speaker?
There is no truth about morality
Other than that? And
Everyone has their own opinion about morality, so you can’t trust anyone’s moral reasoningis an inference that defeats itself, again. We can be sure that these are not truths. We have no way of proceeding from this observation, however, to any positive, substantive moral views.
There are subtler ways to look for self-defeat, too. The empiricist slogan
All knowledge comes from the sensesis unlikely to be justified by appeal to sense experience. You do not look around and observe trees, houses, and knowledge. Foucault used to say things like
Truth-claims are attempts to exercise social powerand this leads you to wonder how to read Foucault’s books. Cautiously, I guess. Hume (and Nagarjuna!) argued that
There is no stable, persisting self.Sez who? Likewise for
Language never captures reality, andIn fairness, Nagarjuna seems clear that even these doctrines will have to be relinquished. They are “true” in the Buddhist sense that they assist in enlightenment, not in the sense that they capture an unfalsified reality. (One wonders what to think, though, about “these doctrines assist in enlightenment.”)
Conceptual thought always falsifies.
Now with all that background, I will leave it as an exercise for the reader to go back over Keller’s rendition of the religious pluralist’s views:
The content of religious doctrines does not matterand see if they are self-defeating, in obvious or subtle ways. Comments welcome.
Each religion sees part of spiritual truth, but none sees the whole
Religious belief is too culturally conditioned to be ‘truth’
It is arrogant to insist that your religion is right and to convert others to it
It is ethnocentric to believe that our religious views are superior to others