statements into phenomenal ones proved not to be forthcoming, however. Chisholm offered a reason why they would not be: what appearances a physical state of affairs (e.g., objects arrayed in a room) has depends both on physical conditions of observation (e.g., lighting) and physical conditions of the perceiver (e.g., of the nervous system). At best, a statement solely about phenomenal appearances is equivalent to one about a physical state of affairs, only when certain physical conditions of observation and certain physical conditions of the perceiver obtain. Materialism. Two problems face any monism: it must characterize the phenomena it takes as basic, and it must explain how the fundamental phenomena make up non-basic phenomena. The idealist and neutral monist theories proposed thus far have faltered on one or both counts. Largely because of scientific successes of the twentieth century, such as the rebirth of the atomic theory of matter, and the successes of quantum mechanics in explaining chemistry and of chemistry in turn in explaining much of biology, many philosophers today hold that materialism will ultimately succeed where idealism and neutral monism apparently failed. Materialism, however, comes in many different varieties and each faces formidable difficulties. Logical behaviorism. Ryle ridiculed Cartesianism as the view that there is a ghost in the machine (the body). He claimed that the view that the mind is a substance rests on a category mistake: ‘mind’ is a noun, but does not name an object. Cartesianism confuses the logic of discourse about minds with the logic of discourse about bodies. To have a mind is not to possess a special sort of entity; it is simply to have certain capacities and dispositions. (Compare the thesis that to be alive is to possess not a certain entity, an entelechy or élan vital, but rather certain capacities and dispositions.) Ryle maintained, moreover, that it was a mistake to regard mental states such as belief, desire, and intention as internal causes of behavior. These states, he claimed, are dispositions to behave in overt ways. In part in response to the dualist point that one can understand our ordinary psychological vocabulary (‘belief’, ‘desire’, ‘pain’, etc.) and know nothing about the physical states and events in the brain, logical behaviorism has been proposed as a materialist doctrine that explains this fact. On this view, talk of mental phenomena is shorthand for talk of actual and potential overt bodily behavior (i.e., dispositions to overt bodily behavior). Logical behaviorism was much discussed from roughly the 1930s until the early 1960s. (While Ryle is sometimes counted as a logical behaviorist, he was not committed to the thesis that all mental talk can be translated into behavioral talk.) The translations promised by logical behaviorism appear unachievable. As Putnam and others pointed out, one can fake being in pain and one can be in pain and yet not behave or be disposed to behave as if one were in pain (e.g., one might be paralyzed or might be a ‘super-spartan’). Logical behaviorism faces similar difficulties in translating sentences about (what Russell called) propositional attitudes (i.e., beliefs that p, desires that p, hopes that p, intentions that p, and the like). Consider the following sample proposal (similar to one offered by Carnap): one believes that the cat is on the mat if and only if one is disposed to assent to ‘The cat is on the mat’. First, the proposed translation meets the condition of being purely behavioral only if assenting is understandable in purely behavioral terms. That is doubtful. The proposal also fails to provide a sufficient or a necessary condition: someone may assent to ‘The cat is on the mat’ and yet not believe the cat is on the mat (for the person may be trying to deceive); and a belief that the cat is on the mat will dispose one to assent to ‘The cat is on the mat’ only if one understands what is being asked, wants to indicate that one believes the cat is on the mat, and so on. But none of these conditions is required for believing that the cat is on the mat. Moreover, to invoke any of these mentalistic conditions defeats the attempt to provide a purely behavioral translation of the belief sentence.
Although the project of translation has been abandoned, in recent years Dennett has defended a view in the spirit of logical behaviorism, intentional systems theory: belief-desire talk functions to characterize overall patterns of dispositions to overt behavior (in an environmental context) for the purposes of predicting overt behavior. The theory is sometimes characterized as supervenient behaviorism since it implies that whether an individual has beliefs, desires, intentions and the like supervenes on his dispositions to overt behavior: if two individuals are exactly alike in respect of their dispositions to overt behavior, the one has intentional states if and only if the other does. (This view allows, however, that the contents of an individual’s intentional states – what the individual believes, desires, etc. – may depend on environmental factors. So it is not committed to the supervenience of the contents of intentional states on