Monday, December 20, 2010

Propositional Attitudes

When Bertrand Russell coined the phrase “propositional attitude” in his 1921 book The Analysis of Mind, he wasn’t thinking of “proposition” in the sense of a piece of language. He was thinking that what was represented was a situation or what would today most likely be called a “state of affairs,” a way the world could be. However several considerations led subsequent philosophers of mind to take a much more literal view of propositions as linguistic entities and as the objects of the attitudes.

Think of a tiger. Alright: now, how many stripes does your imaginary tiger have? Probably your “mental image” of a tiger turned out not to have a specific number of stripes. But a pictorial representation of a tiger would have to. Linguistic (formal) systems can include relevant information and need not contain irrelevant information, an obvious adaptive advantage over isomorphic (pictorial) representation. Formal representation was more congenial to the operationalists (such as computationalists) who wanted to develop functional models of cognition. Then in the late 1950s the linguist Noam Chomsky, critiquing behaviorism, made the enormously influential proposal that formal syntactical structure was “generative”: grammatical forms like “The_is_the_” allowed for multiple inputs and thus indefinitely many (linguistic) representations. Taken to its extreme this argument appears to show that it is necessary for a being to have a formal system for generating propositions to be capable of being in an intentional state at all. Finally the argument that it is propositions that have the property of meaning and that it is propositions that bear logical relations to each other made it seem that a linguistic theory of representation made progress on the mind-body problem.

On my view this is mistaken: the representational model of mind, by definition, locates “mental content” “in the head.” The basic metaphysical problem with the representational model has by now been made clear: “meaning,” what I have been calling the “intentional property” or the “semantic property,” is an irredeemably non-physical “property” that must be washed out of any naturalistic theory of mind. Once one recognizes that intentional predicates are predicated of whole persons – once one sees that positing mental representations necessarily commits the mereological fallacy – the matter is settled. However there is a tight network of arguments and assumptions about intentional states as “propositional attitudes” that will have to be disentangled to the satisfaction of readers who are disposed to defend representations.

The defender of propositional attitudes will start by pointing out that intentional states can only be individuated by virtue of their respective contents. What makes Belief X different from Belief Y is that X is about Paris and Y is about fish. This looks like a block to reduction: to correlate electrochemical activity in the brain, say, with Belief X, we must already be able to specify which belief Belief X is. We don’t have any way of getting from no-content to content (from the non-mental to the mental). This motivates the problem of mental causation: it appears that the content (meaning) of the proposition is what plays the causal role in the production of behavior: when told to proceed to the capital of France he went to Paris because he believed that “Paris is the capital of France.” All the explanation in physical (neurophysiological) terms one could possibly make wouldn’t be explanatory if it didn’t at some point reveal the meaning that is expressed in the proposition, and it doesn’t: “He believes that Paris is the capital of France” is not shorthand for a causal chain of neurophysiological processes.

Donald Davidson famously pointed out a further problem for the development of “psychophysical laws” (as he called them), laws that systematically identified brain processes with particular instances of intentional thought: no one propositional attitude could ever suffice as the discrete cause of a behavior because the causal implication that the propositional attitude has for the acting subject necessarily emerges from the logical relations that that “attitude” has with all of the other intentional states of the subject. Davidson’s phrase for this was “meaning holism,” the view that meaning (in the sense of explanatory psychological predication) is a property of networks of propositional attitudes, not of individual ones. There is not an assortment of individual intentional states in a person’s mind such that one or another might be the proximate cause of behavior; each person has one “intentional state,” the sum of the logically interrelated network of propositional attitudes.

Propositions are the bearers of logical relations with each other. Physical objects and processes, the argument goes, have no logical relations with each other. To believe that the drinking fountain is down the hall is to have the attitude towards the proposition “The drinking fountain is down the hall” that it is true, and to have a desire for water is to have the attitude towards “I have water” that one wants to make that proposition true. The explanatory utility of the intentional predicates – in this case the ability to make an inference from their coincidence that, all other things being equal, the subject will form an intention to walk to the fountain (that is, to make the proposition “I have walked to the fountain” true) – depends on the meaning of the propositions.

Of course making such an inference from the logical relationship between the two propositions also requires that we make a rationality assumption: we must assume about the subject that he, too, will appreciate these logical relations. That is part of the metaphysical “problem of rationality.” I cannot pretend that the distinction between the problem of rationality and the problem of representation is entirely clear-cut, but at this point I need only present a semantic for intentional predicates that locates logical relations out in the world rather than in the head; that will suffice to defeat the argument that mental content is necessary to explain the causal role of intentional states. The further metaphysical problem about the supposed lack of any correlation between the (contingent) physical relationships between states and processes in the body and the (necessary) logical relationships between propositions is dealt with in the discussion of the problem of rationality that is the second half of this chapter.

The terminal station for the line of argument that meaning is an indispensable property (and thus that representations are an ineliminable feature) of intentional explanation is Platonic realism about propositions. On this view, their role as individuators of intentional attitudes and as bearers of logical relations demonstrates that propositions are matter-independent, mind-independent “abstract objects,” ineliminable from ontology. Taking concrete sentences as the “tokens” and propositions as the “types,” the Platonic realist argues that propositions resist a standard nominalist treatment: a “proposition” cannot be simply the name of the set of all of the concrete sentences that express it. The Platonic realist appeals to our intuition that an unexpressed proposition is still a proposition. The fact that propositions can be translated into multiple languages is taken as a demonstration that propositions are not identical to their concrete sentence exemplars.

Wittgenstein proposes an alternative, behaviorist account of language. Wittgenstein’s famous dictum is that meaning is use. The “meaning” of a word, on this view, is whatever the user (speaker or writer) of the word accomplishes by the action of using the word. This alternative to traditional theories of meaning is often called “functional-role semantics.” Wittgenstein rejects the Platonic picture of concepts as essences: the property-in-itself, as distinct from any and all of the concrete exemplars of the property. Language use, he argues, is a type of behavior that reflects a “mode of life,” in the present case the mode of life of human beings. There are no essential meanings (there is no such thing as “meaning” in the traditional sense at all), just patterns of human behavior that can be roughly sorted out on the basis of resemblances and shared histories (these are language “games”). We may gather together statements about “justice” and note that they have similar contexts of use and similar implications for action, just as all of the members of a family can be linked through chains of family resemblance, but that is all. There can be no representation of justice because there is nothing to represent, just as a family of human beings has no “family avatar.” This argument generalizes to all words and their uses, not only those that we think of as naming “concepts.”

If this is right then we are entitled to nominalism about “propositions” after all. A proposition is nothing more than all of the sentence-tokenings of that particular string of symbols. In fact language loses its supposed “interior,” the meaning traditionally supposed to be within or behind the symbol, just as “mind” can now be seen as intelligible patterns of behavior of persons rather than as something “in the head.” Wittgenstein’s vision was to see everything as surface only, both in the case of mind and in the case of language. Psychological description and explanation, understood as an intersubjective discipline limited by the limits of language itself, was necessarily operational.

Now I can sketch out the first natural semantic, the one that replaces intentional predicates that attribute mental representations to persons.

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