I used to think that it’s quite possible that all our mental representations of the world are propositional in nature. To do that, I had to have a broad notion of proposition, much broader than what we normally consider to be linguistically expressible. Thus, I was quite happy with saying that Picasso’s Guernica expresses a proposition about war, a proposition that cannot be stated in words. Similarly, I was quite fine—my Pittsburgh philosophical pedigree comes out here—with the idea that an itch or some other quale might represent the world propositionally.
That broad view of propositions still sounds right. But I am now thinking there is a different problem for propositionalism about our representational states: the problem of estimates. A lot of my representations of the world are estimates. When I estimate my height at six feet, there is a proposition in the vicinity, namely the proposition that my height is exactly six feet. But that proposition is one that I am quite confident is false. There are even going to be times when I wouldn’t even want to say that my best estimate of something is approximately right—but it’s still my best estimate.
The best propositionally-based of what happens when I estimate my height at six feet seems to me to be that I believe a proposition about myself, namely that my evidence about my height supports a probability density whose mean is at six feet. But there are two problems with this. First, the representational state now becomes a representation of something about me—facts about what evidence I have—than about the world. Second, and worse, I don’t know that I would stick my neck out far enough to even make that claim about evidence unequivocally—my insight into the evidence I have is limtied. Moreover, even concerning evidence, what I really have is only estimates of the force of my evidence, and the problem comes back for them.
So I think that estimating is a way of representing that is not propositional in nature. Notice, though, that estimates are often well expressible through language. So on my view, linguistic expressibility (in the ordinary sense of “linguistic”—maybe there is such a thing as the “language of painting” that Picasso used) is neither necessary for a representation of the world to be propositional in nature.
I now wonder whether vagueness isn’t something similar. Perhaps vague sentences represent the world but not propositionally. But just as we can often—but not always—reason as if sentences expressing estimates expressed propositions, we can often reason as if vague sentences expressed propositions. The “logic” of the non-propositional representations is close enough to the logic of propositional ones—except when it’s not, but we can usually tell when it’s not (e.g., we know what sorts of gruesome inferences not draw from the estimate that a typical plumber has 2.2 children).
