Jennifer asked:

I'm writing a paper agreeing with A.J. Ayer. I need to show why statements that can't be proven true
or false are nonsensical. Please help!

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You are, I think, talking about the "verifiability principle of meaning." That is the theory that a
non-tautologous statement is meaningful if and only if it is verifiable in principle. This is the theory that
Ayer advances, and you should notice that it is not about provinga statement true or false, but about
the statement's verifiability. That's different and important. A statement can be "verifiable" and not be
"verified" or proved. For instance, the statement that Julius Caesar sneezed before he crossed the
Rubicon cannot be verified (proved) because we have no records or other information that would tell
us whether it was, in fact, true, and besides, it may be actually false. But true or false, it is "verifiable
in principle," in that we can certainly think of ways in which we might be able to verify (or falsify) it. For
instance, we might find a diary written by a Roman soldier which has the entry, "We are just about to
cross the Rubicon and Caesar sneezed!" So, even if it is impossible — in fact — to verify or prove
that statement, it is verifiable in principle, and therefore, by the verifiability principle of meaning,
meaningful or not nonsense.

But now we have cleared that up, your question arises. Your question really is, why should we accept
the verifiability principle of meaning(fulness)? Consider the statement, "Ontogeny recapitulates
phylogeny." Do you know what it means? To anyone who does not know much biology, it looks like
meaningless nonsense. It isn't. Biologists know what it means. (I won't tell you here, though.) The
verifiability theory tries to explain why that statement (despite appearances to the contrary) is
meaningful. It is meaningful because biologists, at any rate, know what kind of sense experiences it
would take to confirm that statement, or alternatively, disconfirm it. It is, in other words, testable in
terms of experience.

But now consider a famous example make up by the philosopher, Bertrand Russell: "Quadruplicity
drinks Procrastination." Notice that statement is made up of English words each of which is
meaningful (we can find their meanings in a dictionary) But that whole statement is meaningless
nonsense. Why? Ayer's explanation is that it is unverifiable even in principle because we cannot think
of any sense experiences which would give us reason to believe that statement is true or false. The
reason is, of course, that the "statement" made up by Russell is not really a statement at all. It is
neither true nor false. It is a meaningless collection of meaningful terms which only appears to be
meaningful. It is very different from the biological statement I mentioned before. That statement may
look meaningless, and may be "meaningless to you," just because you don't know what it would take
to decide whether it was true or false, or even likely to be true or likely to be false. But biologists
know, and therefore that statement is meaningful.

We might summarize all this by saying that Ayer believes that the meaning of a (non-tautologous)
sentence is, or consists in the method of its verification; the way we would try to determine whether or
not it was true or false. So, if it is impossible to verify or falsify such a sentence, even in theory or
principle, that sentence is meaningless nonsense.

Let me end by noting three things:

First: The terms "meaningless" and "nonsense" are technical terms. They strictly mean unverifiable in
experience. They do not mean, "unimportant" or "insignificant." To take one example: on the
verifiability principle, the sentence "Please close the door," is unverifiable in principle because it is a
request, and not meant to be a statement at all. It is not nonsense in the ordinary sense of the word
"nonsense." But it is unverifiable, and so, "meaningless" in that sense. Ayer would also say that the
sentence, "God exists," is unverifiable and nonsense. Clearly, that sentence is importantly meaningful
in many ways to many people, although it is, unverifiable in principle, and therefore, by the verifiability
principle of meaning, nonsense. Important nonsense, but nonsense all the same.

Second, we should really talk about sentences and not statement as meaningless or not. A statement
is a sentence that is true or false, and so, when we call say that a sentence is a statement we have
already decided it is meaningful. There can be no nonsensical statements, but there can be
nonsensical sentences.

Third: As I indicated in the beginning, the verifiability principle of meaning does not apply to
"tautologies" like "All dogs are dogs," or "All husbands are males." Those are not verifiable or
unverifiable, since they are true or false because of the meanings of their constituent terms.

Kenneth Stern