Some sentences, whether or not they are about other things, are about themselves. They refer to themselves. Hence we say they are 'self-referential.' The phenomenon of sentential self-referentiality is sometimes benign. One example is 'This sentence is true.' Another is 'Every proposition is either true or false.' Of interest here are the more or less malignant forms of self-reference. One example is the so-called Liar sentence:

1. This sentence is false.

If (1) is true, then it is false, and if false, then true. This is an example of an *antinomy*. In pursuit of a taxonomy, we might call this Grade I of self-referential inconsistency. Grade I, then, is the class

of self-referentially inconsistent sentences that issue in antinomies.

There are other self-referential sentences that are not antinomies, but imply their own necessary falsehood. These are such that, if true, then false, and if false, then false, and are therefore necessarily false. For example,

2. All generalizations are false.

If (2) is true, then, since (2) is itself a generalization, (2) is false. But its falsity does not imply its truth. So, if false, then false. Assuming Bivalence, it follows that (2) is necessarily false, whence it follows that its negation -- Some generalizations are true -- is necessarily true, and moreover an instance of itself. A second example might be

3. There are no truths.

If (3) is true, then it is false. And if false, then false. So, (3) is necessarily false, whence it follows that its negation -- There are truths -- is necessarily true.

Examples (2) and (3) belong to Grade II in my tentative taxonomy. These are self-referential sentences that entail their own necessary falsehood. Grade III comprises those self-referential sentences that are such that if true, then neither true nor false, and if false, then false. For example,

4. There are no truth-bearers.

If (4) is true, then, since (4) is a truth-bearer, (4) is neither true nor false. But if false, then false. If we define the cognitively meaningful as that which is either true or false, then (4) is either cognitively meaningless or false. A more interesting example that seems to belong in Grade III is the Verifiability Principle of the Logical Positivists:

5. Every cognitively meaningful sentence is either analytic or empirically verifiable in principle.

If (5) is supposed to be cognitively (as opposed to emotionally) meaningful, and thus not a mere linguistic recommendation or pure stipulation, then it applies to itself. So if (5) is true, then (5) --

which is clearly neither analytic nor verifiable -- is meaningless. So, if true, then meaningless, and if false, then false. Therefore, either meaningless or false. Not good!

Grade IV comprises those self-referential sentences that can be described as self-vitiating (self-weakening) though they are not strictly self-refuting. For example,

6. All truths are relative.

If (6) is true, then (6) is relative, i.e., relatively true. It is not the case that if (6) is true, then (6) is false. So (6) is not self-refuting. Nevertheless, (6) is self-vitiating in that it relativizes and thus weakens itself: if true, it cannot be absolutely true; it can only be relatively true. It is therefore a mistake, one often made, to say that he who affirms (6) contradicts himself. He does not. He would contradict himself only if he maintained that it is nonrelatively true that all truths are relative. But no sophisticated relativist would say such a thing. Other examples which seem to fall into the category of the self-vitiating:

7. Every statement is subject to revision. (Quine)

8. Every theory reflects class interests. (Marxism)

9. All theory is ideology. (Marxism)

10. Nothing can be known.

11. Nothing is known.

12. Nothing is certain.

13. All truth is historical.

14. All is opinion.

What is wrong with self-vitiating propositions? What does their weakness consist in? Consider (8). If (8) is true, then the theory that every theory reflects class interests itself reflects class interests. Suppose (8) reflects the class interests of the proletariat. Then what is that to me, who am not a proletarian? What is it to anyone who is not a proletarian? If (8) is true only for you and those with your interests, and your interests are not my interests, then I have been given no reason to modify my views. The trouble with (7)-(14) and their ilk is that they make a claim on our rational attention, on our common rational interest, while undercutting that very claim.

It seems we need a fifth category. The sentences of Grade V are such that, if they are true then they are, not false, and not self-vitiating, but non-assertible. Consider

15. No statement is negative.

(15) applies to itself and so at first appears to refute itself: if (15) is true, then it is false. And if false, then false; hence necessarily false. But consider a possible world W in which God destroys all negative statements and makes it impossible for anyone to make a negative statement. In W, (15) is true, but non-assertible. (15) does not prove itself to be false; it proves itself to be non-assertible.

Can the same said of

16. All is empty (Buddhism)?

I think not, for reasons supplied here.

Finally, we consider

17. All memory reports are deceptive.

This is subject to the retort that one who asserts (17) must rely on memory, and so must presuppose the reliability of the faculty whose reliability he questions by asserting (17). For if anyone is to be in a position responsibly to affirm (17), to affirm it with a chance of its being true, he must remember that on some occasions he has misremembered. He must remember and remember correctly that some of his memories were merely apparent. It seems obvious, then, that the truth of (17) is inconsistent with its correctly being affirmed as true. If true, it is unaffirmable as true. But this is different from saying that (17), if true, is false. Although (17) is unaffirmable or non-assertible if true, it seems that (17) could be true nonetheless.

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