Wednesday, April 04, 2007

What does it take to believe a proposition?

Just yesterday I read about a recent Newsweek poll according to which almost half of Americans deny the theory of evolution and over a third of college graduates believe that the Biblical creation story is true. These finding are, of course, rather disturbing for many reasons that I do not plan on going into here. But they got me thinking about a different issue: If someone were to ask me to state what the theory of evolution is, I don't think that I would be able to. I know the following: There is a theory, the theory of evolution, such that most scientists believe it be true because, they say, it is the best explanation of a number of facts of various sorts (biological, geological, etc.). Presumably I can, on the basis of the evidence I have, come to know (or at least reasonably believe) that the theory of evolution is true and that the theory of evolution is the best explanation of a number of facts of various sorts. However, given that I am unable to state what the theory of evolution says, it seems that I am unable to know or reasonably believe the theory of evolution itself since it seems that I am unable to believe that theory at all.

Let me make a few clarificatory remarks. I accept latitudinarianism about de re belief. In other words, I think it is very easy to have beliefs about particular things. If there is a shortest spy and I introduce the name 'Shorty' by saying "Let 'Shorty' refer to the shortest spy", then I can believe things about the shortest spy; that is, I can believe things about the guy out there who is the shortest spy. For instance, I can believe that he is the shortest spy, that he is less than 6' tall, and so forth. In other words, on my view de re belief is really easy. (I should note that I also think that so-called de rebus belief is really easy as well. If there are some spies that are shorter than 6' tall and I introduce the plurally referring name 'Shorties' by saying "Let 'Shorties' refer to the spies that are shorter than 6' tall", then I can believe things about the spies who are shorter than 6' tall. For instance, I can believe that they are the spies that are shorter than 6' tall, that each of them is shorter than 6' tall, and so forth.)

I take it that many non-latitudinarians would deny that I can have any beliefs about the theory of evolution at all because I am not well enough "acquainted" with that theory to have such beliefs. I deny this since I think that I do have beliefs about the theory of evolution; for instance, I believe that it is true. So, the issue I'm raising here is not an issue concerning whether I can have beliefs about the theory of evolution. I think that I can have such beliefs. Rather, the issue is whether I can believe the theory of evolution, given my ignorance concerning how to state it.

It will, perhaps, be helpful when considering this question to take scientific theories to be conjunctive propositions. (Or, perhaps, sets (or pluralities) of propositions. If they are sets (or pluralities) of propositions rather than propositions, then I take it that someone believes a scientific theory just in case he believes each of its members (or just in case he believes each proposition that is one of the scientific theory) and a scientific theory is true just in case each of its members are true (or just in case each proposition that is one of the scientific theory is true).) I take it that it is only if we take scientific theories, such as the theory of evolution, to be propositions that it makes sense to talk, as we usually do, about believing a scientific theory (modulo my remarks about sets or pluralities of propositions). So let us assume, for the sake of argument, that scientific theories are conjunctive propositions.

(I should note that the view that scientific theories are conjunctive propositions (or sets or pluralities of propositions) is a controversial one. As far as I am able to discern from the philosophy of science I've learned, many philosophers of science reject this view. Some hold rather that scientific theories are a set methods for explaining phenomena. I do not have space to do this view justice. However, it seems to me that this view has a difficult time making sense of the way we speak about scientific theories; in particular, it has difficulty making sense of the fact that we often talk about believing scientific theories and we often talk about scientific theories as being true or false.)

Back to the main line of argument. I claim that although I can have beliefs about the theory of evolution, which I take to be some particular conjunctive proposition, I cannot believe the theory of evolution given my inability to state that theory. Is this so?

Here is a sort of argument for my view. Suppose that there is a language of thought. Call it "Mentalese". Someone believes a proposition just in case he or she has a Mentalese sentence that expresses that proposition in his or her belief box. A Mentalese sentence expresses a proposition only if its syntactic structure corresponds to the structure of that proposition, its syntactic constituents express the constituents of that proposition, and its syntactic constituents are arranged in the right way. (I add the last clause because, presumably, the Mentalese sentence that expresses the proposition that John loves Mary and the Mentalese sentence that expresses the proposition that Mary loves John have the same syntactic structure and their syntactic constituents each express the constituents of both propositions.) Now it seems to me that the fact that I am unable to state the theory of evolution provides good evidence to think that I have no Mentalese sentence in my belief box expressing the theory of evolution that satisfies these conditions and thus provides good reason to think that I have no Mentalese sentence in my belief box that expresses the theory of evolution.

Notice that this is not to say that I have nothing in my belief box that expresses the theory of evolution. I think I do. In particular, I think that I have a Mentalese singular term that expresses the theory of evolution and that, in virtue of this, I am able to believe things of the theory of evolution. However, this is not sufficient to allow me to believe the theory of evolution, I say, because surely there will be syntactic rules specifying which Mentalese expressions are sentences (well-formed formulas, if you like) according to which a Mentalese singular term is not a Mentalese sentence. And, as I have claimed, one can only believe a proposition if one has a Mentalese sentence in one's belief box that expresses that proposition.

Anyway, what do the rest of you think? What does it take to believe a proposition? Do I believe the theory of evolution or simply believe that it is true?

7 Comments:

Blogger Brad said...

I think you want to say that the problem is not just that you cannot state the theory, but that even if you could state it you would not understand it. That is, on one sense of "cannot state the theory" it is false that you cannot state it, since all you need to do is look up some canonical biological reference work and read it out. Here again we have the distinction between believing that what you read out is true, and believing what you read out. Your general line of thought is tempting; it seems right to say that you can't believe what you read out if you do not understand it.

I have reservations though concerning the implications taking this line would have for the beliefs of scientists themselves. Consider for example theoretical physics and mathematics. I would be surprised if many theoretical physicists or mathematicians had anything like propositional knowledge of the kind you are requiring in the case of evolution, with respect to the theories they believe. On the face of it it seems reasonable to say that physicists and mathematicians believe vast tracts of the orthodoxies in their field without being able to state them, and in some cases without being capable of understanding them without an investment of further intellectual resources. Your view would entail not only that most of us non-scientists do not believe most scientific theories, but that many (if not most) scientists do not either.

One way to mitigate this consequence would be to point out that for many theories there is a minimal set of propositions that would suffice to express the heart of the theory, and that many of us do understand and believe these. For example in the case of evolution, I assume that you believe in common descent, inheritance, natural selection, and so on. Perhaps you could not state these in the form most biologists would, but this seems enough for you to believe in evolution, if not the precise form it takes in the biological literature. (I don't think this would get you very far in the case of mathematics and physics though).

2:01 PM  
Blogger Joshua said...

I Think I hold your view. We talked about this while ago (way back when we were taking the AAA class from Ed). The view that I expressed at the time was that you could know of the theory of evolution that it was true but that you did not know the theory of evolution. I claimed that you could introduce a name, 'EVO' say, for the theory of evolution and know that EVO is true (by testimony perhaps). But I claimed that you didn't thereby know the theory of evolution. This is because its stucture is much different from that of the proposition that EVO is true.

I have a bit of a worry about this view now. I am inclined to think that 'knows' expresses the same thing in the sentences 'Fred knows that Grass is green' and 'Fred knows Mary'. Moreover, I guess I am inclined to think that this kind of knowledge is pretty easy to come by as well. It is interesting to ask how easy it is to come by and whether this undermines the thesis that you and I seem to agree on concerning scientific theories.

4:15 PM  
Blogger rock* said...

Joshua,

I am inclined to agree with you that "knows" expresses the same relation in sentences such as "Fred knows that grass is green" and "Fred knows Mary". I also agree with you that this second sort of knowing is rather easy to come by. (By speaking of sorts of knowing, I don't mean to go back on my claim that "knows" expresses the same relation in both cases. However, I am inclined to think that the reason that "knows" expresses the same relation in both cases is that it expresses a disjunctive relation. So, in saying that the second sort of knowing is rather easy to come by, I mean that it is easy to bear the second disjunct of this relation to something. On the other hand, even if the knowing relation were not disjunctive, I think I would appeal to adverbial modification to distinguish between the different sorts of knowing I am invoking.) So, I guess that I agree that I know the theory of evolution, albeit only because I bear the second sort of knowing to it. However, I'm still inclined to think that I fail to bear the first sort of knowing to it. I'm also inclined to deny that I believe the theory of evolution, since I don't think that there is an analogue to the second sort of knowing for belief.

So, my position is that I know the theory of evolution, but I do not believe it. Thus, I deny the following claim:
Necessarily, for all x and y, if y is a proposition and x knows y, then x believes y.
Some may think that this denial is odd. However, I think that distinguishing between different sorts of knowing makes it less odd.

8:23 AM  
Blogger rock* said...

Brad,

Let me point out before getting to my main response to your comments that the main point I was trying to make in my post was a general one rather than a claim about my position with respect to the theory of evolution. In particular, I wanted to defend the claim that one may believe of some proposition that it is true without thereby being in a position to believe that proposition. Although I claimed that I am in that position with respect to the theory of evolution, I might have chosen other examples to illustrate.

I think that you are correct to point out that in some sense of "cannot state the theory of evolution", it is false to say that I cannot state the theory of evolution. Of course, I didn't mean it in that sense when I said that I cannot state the theory of evolution. Rather, I meant something like the following: I am not in a position to state the theory of evolution simply by reflecting on my beliefs concerning biology and considering how to formulate them precisely.

As far as your reservations concerning the implications of my view for the beliefs of scientists and mathematicians, I am inclined to simply accept those implications if they do in fact follow from my view. However, I don't know enough about scientists and mathematicians and their beliefs to judge whether my view has those implications. I guess I would expect, however, that for each scientist or mathematician there is at least one orthodox proposition in his or her field that he or she fails to believe. (Notice that, contrary to the way you phrase your comment, the issue is about belief, not knowledge.) I'm inclined to accept that each scientist and each mathematician fails to believe the corresponding proposition(s).

Finally, you point out that for many scientific theories there is a minimal set of propositions that is the heart of that theory. In the case of the theory of evolution, you mention "common descent", "inheritance", and "natural selection". Notice that for these to be relevant to the issue at hand, they need to be taken as names for propositions. If they are, however, then it is far from clear to me that believe them rather than simply believing them to be true.

4:18 PM  
Blogger Chris Tillman said...

Why believe that 'knows' expresses some sort of disjunctive property? Evidence that 'knows' has two different senses comes from cross-linguistic evidence that I'm sure you are both aware of. So why do you deny it? I assume you would not hold that 'bank' in English expresses a disjunctive property and 'x is at a bank' is true under an assignment for 'x' iff either x is at the side of a river or x is at a financial institution. So whaddup?

12:36 AM  
Blogger rock* said...

Chris,

I take it that the cross-linguistic evidence you mention concerns the fact that other languages contain two words corresponding to the English word "know". Spanish, for instance, contains "conocer" and "saber", the first of which is usually used to express a relation between a person and another person (and thus corresponds to "know" as it occurs in the sentence "Greg knows Chris") whereas the secon is usually used to express a relation between a person and a proposition (and thus corresponds to "know" as it occurs in the sentence "Greg knows that 2+2=4").

As far as I can tell, both the view that "knows" expresses a disjunctive relation and the view that "knows" is ambiguous can explain this data, and it seems to me that their explanations are about as good as one another. After all, if "knows" expresses a disjunctive relation, as the first view maintains, it is unsurprising that there are other languages which contain different words to express the disjuncts of this relation.

Given, than, that the cross-linguistic evidence does little to support one view over the other, the question is whether there is any other reason to prefer either view. I think that there is. In particular, I think that "knows" fails standard tests for ambiguity and that this provides evidence that, in fact, it is not ambiguous.

As for "bank", I think that it passes standard tests for ambiguity, and that this gives us evidence that it is ambiguous.

8:05 AM  
Blogger Chris Tillman said...

So which tests does 'knows' fail that 'bank' passes?

8:48 AM  

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