Topics Language

Question What is the difference between a sentence-type and a proposition? In the literature, sometimes they are used synonymously, sometimes they are differentiated. I can not, for the life of me, figure out what the fundamental difference is, if any. That is, are both bearers of truth? Are both considered abstract objects (nominalists excluded, of course). If they are different, then how are they related to each other, and how are they related to sentence-tokens? Please shed some light on this issue. Thanks. JJ

Accepted:
August 30, 2007

Comments

You might think of a sentence type as an abstraction from lots of individual occurrences of a given sentence. There's fairly clear sense in which in the following:

Fred eats spinach

I've written two sentences, and a fairly clear sense in which I've written just one sentence. In the former sense of 'sentence', we have what are called *sentence tokens*. In the latter sense, we have what are called *sentence types*. That would still be true if the latter of the two above sentences had been written in a different font, or a different font size. More generally, the notion of 'type' here abstracts away from the peculiarities of all the tokens there may happen to be.

Now in addition to all the sentence tokens that there are, one might reasonably suppose that those that are meaningful express something that transcends them: A meaning, a content, or what you will. Thus two synonymous sentences of different languages seem to express the same content, and many philosophers will hold that the content in question is a proposition. If Gottlob Frege is to be believed, then that proposition is an abstract entity that exists independent of any language or languages there may happen to be, and independent of any mind or minds that may happen to grasp it.

Many philosophers before and after Frege, however, are suspicious of "abstract entities", posits that don't seem to have any position in space and time, and that don't seem able causally to interact with anything that is in space or time. Such philosophers might therefore be tempted to find a substitute for such "abstracta" as propositions, and find something that will do the work that Frege wanted propositions to do without the ontological profligacy. Enter sentence types: Maybe these are "abstract" enough to serve as a kind of meaning or content, without having to be thought of as outside space and/or time. Such philosophers will, then, have a reason for using 'proposition' and 'sentence type' interchangeably: Not because these two expressions mean exactly the same thing, but because according to their ontological theory, propositions just are sentence types (just as genes are bunches of DNA, and heat is mean molecular kinetic energy).

A skeptic might challenge this attempt at a reduction in favor of parsimony. After all, she might point out, there are surely propositions that have never been expressed by any sentence token either in English or other languages. (Just think of a *very* complex and obscure proposition.) In what sense might that proposition be seen as an abstraction? And yet there surely is a proposition there to be thought by someone sufficiently bored or determined, and surely that proposition will be true or false depending on how the world is? The proponent of the above-mooted reduction will need to be resourceful to respond to such a criticism. For a more detailed discussion of the issues than I can provide here, please see Linda Wetzel's article 'types and tokens' in the Stanford Encyclopedia of Philosophy.