What We Believe

What philosophers have usually taken us to believe is either propositions or sentences. (There are several uses of "believe" just like there are several uses of "know." In parallel to what we stipulated about "know," namely, that we'll only use it in the sense of knowing that (some proposition), we take beliefs to be beliefs that propositions are true.) Thus, it is rather important to realize that there is no such thing as a proposition.

This morning, I taught philosophy of mathematics, and I presented Benacerraf's argument that there are no numbers. That is parallel to the claim here that there are no propositions.

Why propositions instead of sentences? When I say "snow is white," I am using a different sentence from what someone in France might use ("La neige est blance) or what someone in Germany might use ("Der Schnee ist Weiss) to "say the same thing." What I am interested in is what is being said, not how it is being said. All three sentences "express the same proposition," or, in other words, they "mean the same thing." Propositions are the meanings of sentences.

Therefore, let's turn, for a moment, from propositions to meanings. What is the meaning of "neige"? "Neige," in French, means snow. What is the meaning of "snow"? Snow is water crystallized into particles with hexagonal symmetry under special meteorological conditions. What does "Issues-and-Methods" mean? "Issues-and-Methods" is a course taught in the philosophy department at the University of Arizona. A request for a meaning is a request for an explanation of a certain kind, an explanation of how a word or phrase or sentence is used. A request for a soda is rather different: you want to get an actual soda. That suggests, if the two were parallel, that there is a certain kind of thing a meaning that one is asking for when asking for the meaning of a word, phrase, or sentence. But the two are not parallel: If I ask in English, for a root beer, I hope to get a root beer. If I ask in French for a root beer, I hope to get a root beer. If I ask in English for the meaning of "neige," I hope to get a translation. If I ask in Frence for the meaning of "neige," I hope to get an explanation, and a translation into English would not (at least normally) be appropriate. There is no such thing as the meaning of a word any more than there is such a thing as the explanation of some natural phenomenon: there are many meanings and many explanations appropriate to particular situations.

As a special case of that, there is no such thing as the proposition expressed by a sentence. We do, reasonably and appropriately, ask for explanations and meanings and, at least for some purposes, determine whether two sentences mean the same thing (express the same proposition). We only get into trouble if we let that fool us into thinking we have reason to believe that there is a certain kind of entity, a proposition.

What has any of this to do with the topic of our course? Sense data reports are propositions. When is it appropriate to make a particular sense data report? When you have experienced the appropriate sense data. There are lots of sentences that could, in principle, be used to make sense data reports that are never, in fact appropriate. For example: It seems to me, Shaughan at 2:45 on Tuesday that I, Shaughan, am in my living room listening to music. So, when is it appropriate to use a given proposition to make a sense data report? It is natural (to the extent that raising such peculiar questions at all is natural) to try to answer the question by explaining what the appropriate relation between a proposition (a possible sense data report) and the facts is that makes it appropriate to give the report. Here is "the answer": it is appropriate to report a proposition $P$ when $P$ corresponds to the facts. That is, perhaps, true, but it is misleading and uninformative in a variety of ways. It is a mistake to look for an appropriate general relation between propositions and some other kind of thing to make it a proposition appropriate to report because there is no such thing as a proposition. Each request for a meaning requires a response of a different sort, and each request for an explanation, for a particular sentence that could be used to make a sense-data report, of when it should appropriately be used, requires an explanation of a different sort. The point is perfectly general (about propositions and truth), but our application is to reports concerning sense data.

Many philosophers have tried to answer the question, not seeing that it is a bad question, and they get into trouble. Ayer discusses two kinds of trouble: coherence and correspondence. Reversing his order, let's start with correspondence.

Correspondence

What does a true sentence correspond to? The facts (state of affairs, situation, set of possible worlds including the actual world) (Russell, early Wittgenstein, Braithwaite). If two sentences express the same proposition, then they correspond to the same facts …. That is, facts and true propositions are interchangeable. The point becomes clearer if we switch from truth to belief, since what we believe need not be true. I might actually have a belief that does not correspond to any fact. Thus, beliefs must correspond to possible facts, possible states of affairs, possible situations, or sets of possible worlds. To what possible fact would the belief that there is an artist wearing a bowler now standing in the doorway? To the "possible fact" that there could be an artist wearing a bowler standing in the doorway. (Let's not worry about impossible facts.) There is a possible fact corresponding to every proposition, and a proposition corresponding to every possible fact. Here they are: take a proposition, find a sentence expressing it, say, $P$, and the fact is the fact that $P$. Take a fact, find a sentence that corresponds to it, say, $P$, and the proposition is the proposition that $P$. You would be forgiven for suspecting that the correspondence theory has not explained anything at all.

Many philosophers (Carnap) have concluded that the whole project is hopeless. That is one motivation for

Coherence

Different propositions bear inferential relations to each other (for example, if "Jack and Jill went up the hill," then "Jill went up the hill" and if "taking penicillin usually cures pneumonia" and you have pneumonia, then "taking penicillin will likely cure you.") What propositions we are entitled to assert has to do with what other propositions we are entitled to assert. I might be entitled to assert "It appears to me that I am in a classroom," because I'm entitled to assert "I seem to see a lot of chairs with people sitting in them" and "I believe that I am on campus," or some such. That has the advantage over the correspondence theory of not duplicating what is claimed once as proposition and once as facts. It has an obvious flaw, however, namely that it never breaks out of the circle of words.

Ayer's Final Answer

There is no such general kind as a proposition, and so there is no general answer to the question. Rather, for each proposition, there is an appropriate set of circumstances in which to use it to make an assertion, and we learn the rules for determining appropriateness in ways that are individual to many different kinds of cases.

-- ShaughanLavine - 06 Feb 2007