The term intentional is used by philosophers, not as applying primarily to actions, but to mean "directed upon an object." More colloquially, for a thing to be intentional is for it to be about something. Paradigmatically, mental states and events are intentional in this technical sense (which originated with the scholastics and was reintroduced in modern times by FRANZ BRENTANO). For instance, beliefs and desires and regrets are about things, or have "intentional objects": I have beliefs about Boris Yeltsin, I want a beer and world peace, and I regret agreeing to write so many encyclopedia articles.
A mental state can have as intentional object an individual (John loves Marsha), a state of affairs (Marsha thinks that it's going to be a long day) or both at once (John wishes Marsha were happier). Perception is intentional: I see John, and that John is writing Marsha's name in his copy of Verbal Behavior. The computational states and representations posited by cognitive psychology and other cognitive sciences are intentional also, inasmuch as in the course of computation something gets computed and something gets represented. (An exception here may be states of NEURAL NETWORKS, which have computational values but arguably not representata.)
What is at once most distinctive and most philosophically troublesome about intentionality is its indifference to reality. An intentional object need not actually exist or obtain: the Greeks worshiped Zeus; a friend of mine believes that corks grow on trees; and even if I get the beer, my desire for world peace is probably going to go unfulfilled.
Brentano argued both (A) that this reality-neutral feature of intentionality makes it the distinguishing mark of the mental, in that all and only mental things are intentional in that sense, and (B) that purely physical or material objects cannot have intentional properties -- for how could any purely physical entity or state have the property of being "directed upon" or about a nonexistent state of affairs? (A) and (B) together imply the Cartesian dualist thesis that no mental thing is also physical. And each is controversial in its own right.
Thesis (A) is controversial because it is hardly obvious that every mental state has a possibly nonexistent intentional object; bodily sensations such as itches and tickles do not seem to, and free-floating anxiety is notorious in this regard. Also, there seem to be things other than mental states and events that "aim at" possibly nonexistent objects. Linguistic items such as the name "Santa Claus" are an obvious example; paintings and statues portray fictional characters; and one might ignorantly build a unicorn trap. More significantly, behavior as usually described is intentional also: I reach for the beer; John sends a letter to Marsha; Marsha throws the letter at the cat; Macbeth tries to clutch the dagger he sees. (Though some philosophers, such as Chisholm 1958 and Searle 1983, argue that the aboutness of such nonmental things as linguistic entities and behavior is second-rate because it invariably derives from the more fundamental intentionality of someone's mental state.)
Dualism and immaterialism about the mind are unpopular both in philosophy and in psychology -- certainly cognitive psychologists do not suppose that the computational and representational states they posit are states of anything but the brain -- so we have strong motives for rejecting thesis (B) and finding a way of explaining how a purely physical organism can have intentional states. (Though some behaviorists in psychology and eliminative materialists in philosophy have taken the bolder step of simply denying that people do in fact ever have intentional states; see BEHAVIORISM and ELIMINATIVE MATERIALISM.) The taxonomy of such explanations is now fairly rich. It divides first between theories that ascribe intentionality to presumed particular states of the brain and those that attribute intentional states only to the whole subject .
Many theorists, especially those influenced by cognitive science, do believe that not only the intentionality of cognitive computational states but also that of everyday intentional attitudes such as beliefs and desires (also called PROPOSITIONAL ATTITUDES) inhere in states of the brain. On this view, all intentionality is at bottom MENTAL REPRESENTATION, and propositional attitudes have Brentano's feature because the internal physical states and events that realize them represent actual or possible states of affairs. Some evidence for this is that intentional features are semantical features: Like undisputed cases of representation, beliefs are true or false; they entail or imply other beliefs; they are (it seems) composed of concepts and depend for their truth on a match between their internal structures and the way the world is; and so it is natural to regard their aboutness as a matter of mental referring or designation. Sellars (1963) and Fodor (1975, 1981) have argued that intentional states are just physical states that have semantical properties, and the existent-or-nonexistent states of affairs that are their objects are just representational contents.
The main difficulty for this representationalist account is that of saying exactly how a physical item's representational content is determined; in virtue of what does a neurophysiological state represent precisely that the Republican candidate will win? An answer to that general question is what Fodor has called a "psychosemantics"; the question itself has also been called the "symbol grounding problem." Several attempts have been made on it (Devitt 1981; Millikan 1984; Block 1986; Dretske 1988; Fodor 1987, 1990).
One serious complication is that, surprisingly, ordinary propositional attitude contents do not seem to be determined by the states of their subjects' nervous systems, not even by the total state of their subjects' entire bodies. Putnam's (1975) TWIN EARTH and indexical examples are widely taken to show that, surprising as it may seem, two human beings could be molecule-for-molecule alike and still differ in their beliefs and desires, depending on various factors in their spatial and historical environments. (For dissent, however, see Searle 1983.) Thus we can distinguish between "narrow" properties, those that are determined by a subject's intrinsic physical composition, and "wide" properties, those that are not so determined, and representational contents are wide. So it seems an adequate psychosemantics cannot limit its resources to narrow properties such as internal functional or computational roles; it must specify some scientifically accessible relations between brain and environment. (Though some theorists continue to maintain that a narrow notion of content -- see NARROW CONTENT -- and accordingly a narrow psychosemantics are needed and will suffice for cognitive science; see Winograd 1972; Johnson-Laird 1977; and Fodor 1987. A few maintain the same for the everyday propositional attitudes; see Loar 1988; Devitt 1990.)
A second and perhaps more serious obstacle to the representational view of thinking is that the objects of thought need not be in the environment at all. They may be abstract; one can think about a number, or about an abstruse theological property, and as always they may be entirely unreal. (The same things are true of representations posited by cognitive psychology.) An adequate psychosemantics must deal just as thoroughly with Arthur's illiterate belief that the number of the Fates was six, and with a visual system's hallucinatory detection of an edge that isn't really there, as much as with a real person's seeing and wanting to eat a muffin that is right in front of her.
In view of the foregoing troubles and for other reasons as well, other philosophers have declined to ascribe intentionality to particular states of subjects, and they insist that ascriptions of commonsense intentional attitudes, at least, are not about inner states at all, much less about internal causes of behavior. Some such theories maintain just that the attitudes are states, presumably physical states, of a whole person (Strawson 1959; McDowell 1994; Baker 1995; Lewis 1995). Others are overtly instrumentalist: Philosophers influenced by W.V. Quine (1960) or by continental hermeneuticists maintain that what a subject believes or desires is entirely a matter of how that person is interpreted or translated into someone else's preferred idiom for one purpose or another, there being no antecedent or inner fact of the matter. A distinctive version of this view is that of Donald Davidson (1970) and D. C. Dennett (1978, 1987), who hold that intentional ascriptions express nonfactual, normative calculations that help to predict behavior but not in the same way as the positing of inner mechanisms does -- in particular, not causally (see INTENTIONAL STANCE). Such views are usually defended epistemologically, by reference to the sorts of evidence we use in ascribing propositional attitudes .
Perhaps suspiciously, the instrumentalist views are not usually extrapolated to the aboutness of perceptual states or of representations posited by cognitive scientists; they are restricted to commonsense beliefs and desires. They do shed the burden of psychosemantics, that is, of explaining how a particular brain state can have a particular content, but they do no better than did the representationalist views in explaining how thoughts can be about abstracta or about nonexistents.
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