Stephen Schiffer

Suppose we think in a language of thought. Then Paul Boghossian' is prepared to argue, first, that there may be ambiguous Mentalese expression types that have unambiguous tokens, and, second, that the way in which this is possible allows for otherwise valid theoretical or practical reasoning to be rendered invalid owing to equivocation of a sort that may be undetectable to the reasoner. Paul sees this as a possible basis from which to launch an argument for what some might call "narrow content", and this is a question I'll take up later

If we think in a lingua mentis, questions about relations between linguistic meaning and propositional-attitude content become questions about relations between meaning in a public language (p-meaning) and meaning in a language of thought (t-meaning). Whether or not the neo-Gricean is correct that p-meaning can be defined in terms of t-meaning and then t-meaning defined in terms of the causal-functional roles of mentalese expressions, it's apt to seem obvious that separate accounts are needed of p-meaning and t-meaning, since p-meaning, unlike t-meaning, must be understood at least partly in terms of communication. Paul Horwich, however, claims that his ‘use theory of meaning’ provides a uniform account of all meaning in terms of ‘acceptance properties’ that, surprisingly, implicate nothing about use in communication. But it turns out that the details of his theory belie his claim about it

Although there is a vast literature on whether propositional attitudes are relations to propositions, a crucial question that ought to lie at the heart of this debate is not often enough seriously addressed. This is the question of the contribution propositions make to the ways in which we benefit from having our propositional-attitude concepts, if those concepts are concepts of relations to propositions. Unless propositions can be shown to confer a benefit that no non-propositions could provide, we should probably doubt whether propositional attitudes really are relations to propositions. I believe that propositional attitudes are relations to propositions and that the role played by them in our conceptual economy cannot be played by things of any other kind, and in this paper I try to say why. This paper, in other words, offers my answer to the question posed by my title.

I. Vague Properties and the Problem of Vagueness The philosophical problem of vagueness is to say what vagueness is in a way that helps to resolve the sorites paradox. Saying what vagueness is requires saying what kinds of things can be vague and in what the vagueness of each kind consists. Philosophers dispute whether things of this, that, or the other kind can be vague, but no one disputes that there are vague linguistic expressions. Among vague expressions, predicates hold a special place in the problem of vagueness, for it’s their vagueness that is soritesgenerating. That puts the vagueness of predicates at the hub of the problem of vagueness, and there can be little doubt that we’ll be a short step from home if we can account for it. Any account of vagueness will of course require commitment to theses that are themselves foci of philosophical debate, but one can’t expect to get anywhere without taking on some as working hypotheses and then striving to say something that will be plausible if those hypotheses are plausible. One of the working hypotheses of this paper is that propositional attitudes and propositional speech acts are relations to propositions of some stripe or other, in the generic sense in which a proposition is an abstract, mind- and language-independent entity that has a truth condition, and has that truth condition both essentially and absolutely (i.e. without relativization to anything).1 The existence of propositions requires the existence of properties, in the generic sense in which a property is an abstract, mind- and language-independent entity that has an instantiation condition, and has that instantiation condition both essentially and absolutely. For present purposes it will be harmless to pretend that the propositions we believe and assert are Russellian propositions---structured entities whose basic constituents are the objects and properties our beliefs and speech acts are about. When a propositionalist speaks in loosey-goosey mode, she is apt to say that a sentence token is true just in case the proposition expressed in its utterance is true.