of New Hampshire, Durham, NH 03824-3567. We thank M. ..... This keeps us within the ground rules ... handing over a wallet in response to a gun and "Your.
Behavioral Explanations and Intentional Explanations in Psychology William M. Baum and Jennifer L. Heath University of New Hampshire
A recent criticism of behaviorism asserts that intentional explanations in psychology are acceptable and preferable to behavioral explanations. The philosopher Dennett justifies intentional explanations on the grounds that they are provisional and can be cashed out in principle. Skinner objected to such explanations on the grounds that they are never cashed out in practice. Their different views arise from their divergent goals for psychology: understanding intelligence and rationality versus understanding behavior. In the context of a science of behavior, intentional explanations only give the semblance of explanation because they rely on immediate causes that are fictional. Nonintentional explanations acceptable for a science of behavior are historical, much as in evolutionary biology. When Dennett's argument is applied to evolutionary biology, it becomes a justification of creationism.
Intentional explanations, which attribute behavior to hidden nonphysical causes such as beliefs and desires, have long enjoyed popularity among both laypeople and psychologists. One of Skinner's contributions to scientific psychology was to point out the weaknesses of intentional explanation and to offer a scientifically acceptable alternative: historical explanation. Historical explanations of behavior resemble historical explanations of species in evolutionary biology. Their strength, both in biology and psychology, lies in their confining discussion and inquiry to the physical sphere, a prerequisite for scientific validity. As a basis for scientific psychology, historical explanation has been slow of acceptance. Most psychologists, indeed, seem unaware of Skinner's innovations, supposing instead that nothing new has happened to behaviorism since Watson and that behaviorism is outmoded or dead. One current influence in psychology that fosters intentional explanations is the cognitive view, characteristic not only of cognitive psychology but of many other areas as well. In two books, Brainstorms and The Intentional Stance, Daniel Dennett (1978a, 1987a) lent a philosopher's support to this cognitive view that was so often the target of Skinner's criticisms and so often critical in return. Dennett (1978b) focused directly on Skinner in an essay called "Skinner Skinned" in Brainstorms. Although The Intentional Stance contains little about Skinner, it expands on the earlier views and remains consistent with them. 1312
As was true with Chomsky's (1959) review of Verbal Behavior, behaviorists have made little response, despite ample time (see MacCorquodale, 1970). In Zuriff's (1985) book, Behaviorism: A Conceptual Reconstruction, counterarguments can be found, but one has to look for them, and they are not directed specifically at Dennett. One direct response was made by the philosopher Ullin Place (1987), but the essay was not written from Skinner's point of view, and largely agreed with Dennett. Dennett's (1987b) response to Place indicates he felt no challenge; he was simply able to dismiss the arguments. In this article, we attempt a reply to Dennett that is both adequate and direct. The substance of Dennett's argument in both "Skinner Skinned" and The Intentional Stance is this: (a) Everyday ways of talking about behavior with terms like rationality, intelligence, or belief can provide satisfactory explanations of behavior; (b) it is possible to demonstrate that behavioral explanations involve as much speculation about unknown factors as everyday explanations; and (c) therefore, everyday explanations are just as good as behavioral explanations and are even preferable because they are simple and familiar. To criticize this argument, we take up three topics: (a) Skinner's objections to mentalistic explanations and his probable response to Dennett's criticism, (b) how conflicts between philosophers like Dennett and scientists like Skinner stem from differences in goals, and (c) the strength of historical explanations—that is, explanations that rely on history rather than immediate causes.
Mentalism For most of his professional life, Skinner (1953, 1969, 1974) criticized the practice he referred to as mentalism. He argued that mentalistic explanations, those that appeal to mental objects and events as causes of behavior, cannot suffice for a science of behavior. Understanding his criticisms requires a close look at the way he used the word mental, because it differed from everyday usage. Skinner (e.g., 1974) distinguished mental from private. Private events like thoughts, feelings, imaginings, and recollections are physical, not mental. He occasionCorrespondence concerning this article and requests for reprints should be addressed to William M. Baum, Department of Psychology, University of New Hampshire, Durham, NH 03824-3567. We thank M. Chiesa for helpful comments on an early version of the manuscript.
November 1992 • American Psychologist Copyright 1992 by the American Psychological Association, Inc. 0003-066X/92/S2.00 Vol.47, No. 11. 1312-1317
ally lapsed into everyday usage, which would include private events within the mental category, but in the great majority of instances he used mental to exclude private physical events. For Skinner mental included the nonphysical, the "other stuff" of dualism, the fictional. Opposing mentalism for him meant opposing dualism and "explanatory fictions." Dennett (1978b), like some others before him, missed the distinction between private events and mental events (i.e., fictional events). For example, he wrote, "it turns out that 'mental' means 'internal' means 'inferred' means 'unobservable' means 'private'" (p. 58). Yes, mental means inferred and unobservable. No, it does not mean internal or private. Private events are observable, even if only by an audience of one. They are just as real as public events; thinking about Dennett is as real as writing about him. Mental (fictional) events, in contrast, are unobservable because they are nonphysical; no one can ever observe belief itself or intelligence itself, regardless of claims that they can be inferred from their physical manifestations, public and private. The absence of this distinction, however, does little harm to Dennett's discussion, because he correctly recognized that Skinner objected to belief, intention, and knowledge when they play the role of fictional causes. Mentalistic explanations, according to Skinner, have two objectionable characteristics: superfluity and autonomy. Every mentalism is superfluous in the sense that it only restates an observation. An explanatory fiction is inferred from observed behavior and then said to cause it. A person who is seen carrying an umbrella is said to believe it is going to rain and then is said to carry the umbrella because of the belief. An acceptable explanation for Skinner would point to a preceding event like hearing a weather report or seeing clouds in the sky, rather than an inner belief. As with beliefs, so with another popular form of superfluous mentalism, the internal representation. Behavior that might be explained by external events instead is attributed to internal representations of those events. If a category of stimuli is found to have a common effect on behavior, then the creature is said to have a concept somewhere inside. If we can recollect past external events, we are said to have memory somewhere inside. The concept or memory is then said to cause the behavior. Skinner enjoined us to seek the explanation not in the representation but in the past events recollected and in the histories of such stimulus categories. Laypeople and cognitive psychologists who insist on the existence of representations rarely see that representations in no way explain the behavior they are supposed to explain. They leave two unsolved problems: how a concept or memory can affect behavior and where the concept or memory came from in the first place. Once we have explained the observation by its ultimate origin in past external events, the representations are revealed to be superfluous. Some mentalisms, according to Skinner (1974), have the additional undesirable character of autonomy. An autonomous mentalism is imagined to behave in its own November 1992 • American Psychologist
right, but then its own behavior demands an explanation. Skinner compared it to a homunculus. An inner agent (e.g., personality or self) is said to cause behavior, but the behavior of the agent itself is left unexplained. The behavior of the inner agent is as complex as the behavior it is supposed to explain, so we are no further ahead and probably worse off because the inner agent's behavior cannot be observed. Dennett (1978b) partly agreed with Skinner when he regarded intentional idioms—that is, terms that refer to inner purpose, intelligence, and rationality as causes of behavior. Dennett (1978a) granted, "Intentional theory is vacuous as psychology because it presupposes and does not explain rationality or intelligence" (p. 15). Explaining rational and intelligent behavior by appealing to rationality and intelligence is vacuous because it is circular. Nevertheless, he argued, intentional idioms should be acceptable provisionally, as long as we remember that ultimately they must be cashed out for standard physical terms. Quine (1969) also discussed provisional explanations based on intuitive categories ("similarity notions") in the sciences, not just psychology. He likened them to "unredeemed notes." Examples he considered were solubility in water and intelligence. Such terms, Quine argued, when understood in light of a valid scientific theory, become superfluous: "The same scientific advances that have thus provided a solid underpinning for the definition of solubility . . . have also, ironically enough, made that line of definition pointless by providing a full understanding of the mechanism of solution" (p. 136). As long as the unanalyzed similarity notions have not been cashed out, they remain disreputable. Viewed in this light, the main job of science could be seen as the supplanting of everyday provisional explanations. As can be seen, Skinner was trying to do exactly this with the notion of history of reinforcement. Although Dennett's justification for provisional explanations might be correct logically, it overlooks a fact of life: People rarely see the need for intentional idioms to be cashed out. They rest as if the explanation were complete. Although intentional terms may serve as convenient shorthand, as when a biologist speaks of "selfish" genes (Dawkins, 1976), a scientist avoids them when trying to be precise because they can be deceptive and confusing, especially when applied to human behavior. The selfishness of a gene is much easier to cash out than the selfishness of a person. This is the basis of Skinner's objections to mentalism, which fall into two groups. The first type of objection is that mentalistic explanations impede inquiry. They do this for two reasons. First, they give the appearance of an explanation, with the result that curiosity tends to rest. One is distracted from looking for environmental factors that can be observed and manipulated. Second, they offer for study objects that cannot be observed. Neither memory nor mind can be observed. How shall we study them? Why not look for the factors that affect memory or affect the behavior supposed to be caused by mind? 1313
The second type of objection is that mentalistic explanations are not useful. Here Skinner took his lead from pragmatists like James (1974/1907) and Mach (1960/ 1933), who argued that the value of science lies in its usefulness in making sense of our experience of the world. (See Day, 1980, for explicit discussion of this connection.) "Making sense" of the world meant rendering it simple and familiar by describing it in terms that we find simple and familiar. For Skinner, the science of behavior aimed to make sense of our experience of behavior. Mentalistic explanations failed the simplicity criterion. Being superfluous and themselves requiring explanation, mentalistic explanations, even if familiar, fail to offer the economy of thought necessary to make them useful. For Skinner, describing behavior in terms that are both simple and familiar requires becoming familiar with a more useful vocabulary, one in which observations can be discussed economically. Although Dennett justifies intentional explanations partly by their utility, his notion of utility extends only to their predictive value. Skinner's criterion of utility includes not only prediction, but also economical understanding (making sense). We discuss this difference in greater depth later. Instead of grouping Skinner's objections to mentalism as we have earlier, Dennett maintains that they seem unfocused. This misperception is revealing because it suggests that the two differ at the most fundamental level, their goals. Dennett mistakenly supposes that he and Skinner set the same goals for psychology, when in reality their goals could hardly be more different. Dennett's goal comes clear when he takes up the problem that intentional idioms assume rationality and intelligence. Why is Tom riding the uptown bus? "Because he wants to go to the museum, and he believes this bus will take him there." Dennett (1978b) commented, "Since psychology's task is to account for the intelligence or rationality of men and animals [italics added], it cannot fulfill its task if anywhere along the line it presupposes intelligence or rationality" (p. 58). For Skinner, in contrast, one goal of a science of behavior could be to offer an account of behavior that, in everyday talk, "shows intelligence and rationality." It would not be the main goal, and the category, being one of Quine's (1969) "unanalyzed similarity notions" (discussed earlier), would probably enjoy no special status. The ultimate goal is to understand all behavior. The difference, however, runs deeper than just a difference of scope. In a sense the two lines of thought never engage one another, because Dennett concerns himself with abstractions (rationality and intelligence), whereas Skinner concerned himself with concrete behavior. Skinner's arguments were pragmatic. His goal was not merely to explain rationality and intelligence but to establish a science of behavior. Dennett strives after philosophical truth, and uses true and prove, words that are virtually absent from Skinner's writing. Skinner was after utility, not philosophical truth. Dennett (1978b) asked, 1314
"can men ever be truly said to have beliefs, desires, intentions?" (p. 63). Skinner would ask, "Is it ever useful (i.e., economical, in the sense described above) to say that men have beliefs, desires, intentions?" His answer was always "no." The difference of goals leads to deep misunderstanding, particularly about what constitutes an explanation, which is the subject of this article.
Types of Explanation As the two men's goals diverge, so do their views about explanation. Dennett (1978a) considered explanation to consist of reduction to mechanism. For justification, he relied heavily on the example of the chess-playing computer. Here is a known mechanism that nevertheless could be said to behave purposively—that is, to display rationality and intelligence. It afforded Dennett a model of what it would mean to cash out intentional terms and thereby justify intentional explanations such as "The computer wants to win and believes this move will do the job." To complete the analogy to human behavior, one would have to add, "When the workings of the brain are known the same way the workings of the computer are known, then intentional explanations of human behavior will be similarly cashed out." For Dennett, the philosopher, it is enough that this cashing out be possible in principle. In the first chapter of Brainstorms, using a banking metaphor, he likened "provisional" intentional terms to "loans of intelligence" (cf. Quine's, 1969, "unredeemed notes"). That they could someday be cashed out is his justification for use of intentional terms to explain behavior. Although Skinner never wrote in response to Dennett, his objections are easy to guess. First, the trouble with mentalistic terms, including intentional idioms, is that no one cashes them out in practice. Even if such cashing out of terms might be possible someday, the possibility remains remote. Skinner many times made the argument that a science of behavior need not and should not wait on an understanding of the nervous system. On the contrary, he pointed out that only from the science of behavior will neuroscientists learn what phenomena need to be explained. Second, the example of the chess-playing computer incorrectly holds up reduction to mechanism as the only model of scientific explanation. Skinner, the pragmatic scientist, taking his cue from James and Mach, sought explanations that have greater and more immediate utility. He argued that explanation of a phenomenon usually consists of describing it with a single set of terms. He repeatedly argued that a set of terms defines a science. The terms are all interdependent in the sense that their definitions rely on one another (Baum, 1974). Just as sun, planet, and satellite are interdependent in this way, so are response, stimulus, and reinforcement. Not that reduction to mechanism is wrong or impossible. Cell biologists nowadays talk a lot to biochemists, and someday perhaps behavior analysts will talk similarly to neurosciNovember 1992 • American Psychologist
entists. It is just that such reduction is neither the only nor the usual method of explanation in science. Moreover, whereas intentional explanations need to be cashed out by reduction to physical terms, behavioral explanations carry no such requirement. Neurophysiology can complement behavioral accounts, but cannot replace them, any more than an understanding of genetics and the workings of DNA replaces an evolutionary account of species. (See Lee, 1988, for further discussion of this point.) If reduction were the method of explanation, as Dennett (1978a) implied with the use of the chess-playing computer, then, logically, the science of mechanics would have had to wait for discoveries in atomic physics before it advanced. Moreover, if one applied Dennett's argument in favor of the provisional use of intentional terms, then in the absence of an explanation of gravity at the atomic level, Newton would have been justified in (provisionally!) explaining the falling of a stone by the stone's desire to reach the ground. Applied to the physical sciences, Dennett's logic becomes a justification of animism. Presumably, he would not go so far but only because of the customary (intuitive and unanalyzed) distinction between animate and inanimate things; logically, there would be no reason for restraint.
Historical Vocabulary and Explanation For present purposes, let a single set of interdependent terms be called a "vocabulary." Although he never named them, Dennett (1978a) identified two different vocabularies. The one he favored can be called the intentional (I) vocabulary, and the one Skinner favored can be called the physical (P) vocabulary. In its defense, Dennett (1978a) argued that the I vocabulary possesses the essential ingredient that lends a vocabulary scientific utility: It allows prediction and control. He predicted, for example, "if I were to ask a thousand American mathematicians how much seven times five is, more than nine hundred would respond by saying it was thirty-five" (p. 13). The basis of the prediction, he claimed, is the "fact that men in general are well enough designed both to get the answer right and to want to get it right" (p. 13). He went on to explain that a rat presses a bar in an operant chamber because "the rat desires food and believes it will get food by pressing the bar" (p. 15). These examples illustrate both the aim and the error of mentalistic explanations. The aim is to invent a cause (e.g., capability, desire, or belief) in the present. This aim arises from an unnecessary attachment to a "billiardball" notion of causality (i.e., a cause producing an immediate effect). The error is that the invented cause is a fiction having no intelligible causal connection with the behavior. (How does a belief cause a rat to press a lever?) The great strength of P vocabulary is that it allows physical behavioral events to be tied to physical causes in the environment. This keeps us within the ground rules of normal science and avoids the pitfalls of dualism (i.e., mentalism). November 1992 • American Psychologist
One must, however, take the step of allowing the physical causes to lie in the past—that is, in the history of the behavior. Solving arithmetic problems and lever pressing depend on earlier training. The rat presses the lever because such responses have been reinforced in the past. When asked "How much is five times seven?" a person responds "35," because of several converging histories having to do with numbers, the word times, the correct answering of questions, and the reinforcement of the particular response "35." In comparison with the intentional explanation, such a historical explanation would appear to be complex, but the simplicity of the intentional explanation is apparent; if we ask where the mathematician's knowledge of the correct answer and desire to get the answer right come from, we find ourselves inquiring into the very same history. Skinner (1953; 1974) pointed out that fictional present causes often stand as surrogates for past history. If Dennett insists that a belief causes a response, then one must ask where the belief came from. Of course, it results from past environmental events. If one knew the history, one would no longer need the belief, and as long as one insists on the belief, one deters the effort to identify the relevant history. Dennett insists that P vocabulary cannot deal with the "complexity" of human behavior, as in, for example, our ability to generate novel behavior. Like Chomsky (1959) before him, but with more understanding, Dennett disparages Skinner's (1953) explanation of a person handing over a wallet in response to a gun and "Your money or your life." The basic objection is that the person has never handed over a wallet to a robber before, and therefore the response could not result from a history of reinforcement. Dennett (1987b) remarked, "The Skinnerian must claim that this is not truly novel behavior at all, but an instance of a general sort of behavior which has been previously conditioned" (p. 67). Furthermore, [Skinner] must insist that the "threat stimuli" I now encounter (and these are not defined) are similar in some crucial but undescribed respect to some stimuli encountered in my past which were followed by responses of some sort similar to the one I now make, where the past responses were reinforced somehow by their consequences, (p. 67) This is fairly true. Skinner (1974) would say that a threat like "Your money or your life" is an example of a rule, a verbal discriminative stimulus that points to a contingency—here, a contingency of negative reinforcement. In the past compliance has been negatively reinforced by removal of a threat. Everyone has faced a bully in the playground, a parent who threatens removal of privileges, or a tyrannical boss. A robber may pose an unusual threat, but a threat is a threat, and past learning provides the right response. Historical explanations deal with novelty as variation on a theme. Such a sketch, however, cannot be seen as a full explanation. Rather, it provides a method for arriving at what would ultimately be a complicated account. As with the 1,000 mathematicians, the apparent simplicity of an 1315
intentional explanation appealing to knowledge, belief, and desire would be deceptive; where do these supposed inner causes come from? Dennett (1978a) claimed that mentalistic explanations are just as good as historical explanations in P vocabulary because they are equally speculative. Whereas one type invents a belief or intention, the other invents a history of reinforcement. The conclusion presumably would be that if both are equally speculative, then one should prefer the vocabulary that is more familiar. But Dennett misunderstands the argument in favor of P vocabulary. He complains that Skinner never proves that P vocabulary is superior. This is correct. Skinner argued in favor of P vocabulary on pragmatic (i.e., Jamesian) grounds. It is not a matter of P vocabulary being proved. It is superior on the grounds of simplicity and consistency. Both I vocabulary and P vocabulary can apply to all behavior. When the history is known, P vocabulary provides a simpler account. Consistency takes care of the rest, assuming that one vocabulary is better than two. This is the reasoning behind a quotation Dennett (1978a) cited but misunderstood: "When . . . histories are out of reach, very little prediction and control is possible, but a behavioristic account is still more useful than a mentalistic one in interpreting what a person is doing and why" (p. 329, Footnote 41). It is true that we are often just as much at sea about what history of reinforcement (P vocabulary) might have led to some present behavior as we would be about the purpose or drive (I vocabulary) that produced it, but, Skinner continued, "[If] we are going to guess, it is more helpful to guess about genetic endowment and environmental history." The key words here are useful and helpful. What is guessed at in history can become known or at least can be related to what is known. The great advantage of speculating about history, in contrast to fictional present causes, is that it holds out the possibility of replacing guesswork with observation. Further study can confirm or disconfirm the speculation. Even failing further study, however, speculation about history demystifies a puzzling event by assimilating it to understood phenomena. In scoffing at Skinner's speculative explanations, Dennett overlooks the similarity that Skinner's treatment of everyday behavior bears to the treatment of everyday happenings by the other sciences. One observes an isolated event: an earthquake, a building collapse, an explosion at a chemical plant, or food poisoning. It is compared to already-understood phenomena, especially laboratory phenomena. Speculation as to probable circumstances fits the event with the known phenomena: Most probably this gas leaked into the chemical plant; most probably the food poisoning is from bacterial toxins. With behavior, Skinner took a similar approach. When lever presses have been reinforced in the past only in the presence of a light, lever presses occur frequently when the light is on now. Why do I brush my teeth at night? I was taught to do so by my father, I presume there was reinforcement for doing so then, and there is known reinforcement (of another sort) today. When 1316
the history is unavailable, the behaviorist speculates in the light of what is already known, exactly as in other sciences. In his criticisms of historical explanations, Dennett points to two central problems: similarity and novelty. What makes this response a threat rather than a question? Where do new responses come from? In an account of apparent purpose in terms of variation and selection, these have to do with the nature of variation, of which behavior analysts at present know little. Because, in the absence of information, one guesses at the appropriate history, Dennett would be correct that the explanation offered might be no better than a mentalistic one, were speculative origins the only criterion. Scientists bring in additional criteria, however, such as usefulness. One can see where Dennett's argument leads when applied to the other wellknown example of historical explanation—evolutionary theory. Evolutionary biologists find in the fossil record evidence of evolutionary history. How did legs evolve? The answer is developed by pointing to variation in the appendages offish and the similarity of appendages of some late fishes to some early amphibians. The selection that favored creatures with legs probably had to do with the particulars of exploiting resources on land. In the absence of a fossil record, one speculates still further what the line of descent might have been. Logically, one might argue that such speculative historical explanations are no better than the alternative, the intentional explanations current before Darwin, which appealed to a rational, intelligent Creator. Indeed, creationists insist that in the absence of evidence, it is justified to say that creatures are the way they are because of the rationality and intelligence of God or some other force. A leading contemporary creationist, D. T. Gish (1984), defined creationism as follows: the creationists . . . maintain that outside the universe, and independent of it, there is a being or a creator or force, or whatever you want to call it, that created the universe, created life . . . by processes which are not based upon currently functioning natural laws and processes, (p. 26) This definition in no way requires a literal interpretation of the Book of Genesis. One "sub-model" that Gish (1984) described, called "progressive creationism," suggests "that things really are quite old and that creation took place in steps progressively" (p. 26). The defining attribute of a creationist, therefore, is appeal to intelligence and rationality to explain evolution. The parallel to Dennett's (1987a) argument is striking. On the one hand, there are the creationists attributing the creation of species of'life to an independent intentional force (God or Mother Nature), and on the other hand, there is Dennett attributing the creation of species of behavior to an independent intentional force (self or mind). Just as, before Darwin, many biologists considered the aim of their studies to be the understanding of the rationality and intelligence of the Creator (e.g., Boakes, 1984), so Dennett claims the aim of psychology November 1992 • American Psychologist
to be the understanding of the rationality and intelligence of the self. This is the basis on which Skinner (1990) was justified in saying, "Cognitive science is the creation science of psychology" (p. 1209). Dennett's (1987a) comments about evolutionary biology parallel his objections to Skinner (Dennett, 1978a). Just as behavior analysts speculate about the right history of reinforcement, biologists speculate about the right evolutionary history. Dennett appeals to the rationality and intelligence of the self for the one, and the rationality and intelligence of Mother Nature for the other. He called on us, for example, "to substitute for our interpretive intentions and purposes the intentions and purposes of the organism's designer, Mother Nature" (Dennett, 1987a, p. 301). It is unclear just how seriously one is to take this idea of Mother Nature, but he attempts to justify both appeals on the basis that they are "intelligence-loans" or provisional explanations until all the details of the mind and natural selection are worked out. When Dennett (1987a) applied the same "intentional stance," developed for psychology, to evolutionary biology, he became a creationist, according to Gish's (1984) definition given earlier. Mother Nature constitutes the sort of creative, intelligent, rational "force," independent of the universe, that Gish requires. In fairness, one should note that Dennett put forward his Mother Nature creationism provisionally, to be cashed out at some later time. In contrast, however, to uses of intentional idioms in other contexts, like discussions of selfish genes, no one knows how to cash out Dennett's provisional creationism. It raises the same sound philosophical objections as do other brands of creationism. Intentionality raises more problems than it solves. Without calling him a creationist, Amundson (1990) criticized Dennett's (1988) substitution of intentionality for "selectionist causality," saying that "Intentionality . . . is the most notorious unsolved problem of modern philosophy," that "the tradeoff is not a bargain for biologists," and that the switch to intentionality is a "poisoned pill" (p. 580). Biologists reject more obvious forms of creationism for the reason that Amundson puts forward: An independent creative force replaces a potentially explainable puzzle with the mystery of intentionality. Like Skinner, most evolutionary biologists find it more helpful to speculate about history than about Mother Nature. Is it helpful to accept creationism, even provisionally? Who would seriously suggest that evolutionary biologists should have held onto the intentional idioms that were common before the theory of natural selection? The objection hardly comes up because almost everyone sees that getting rid of intentional idioms represented an advance for biology. If it is absurd to hold onto intentional idioms in biology, it is equally absurd to hold onto them in psychology. Dispensing with intentional explanations constitutes an advance for any science, and that includes a science of behavior.
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A lesson that psychologists can learn from evolutionary biology is that there exists another mode of explanation besides mechanism and immediate causes. The apparent purposiveness of evolution, whether of life forms over millenia or of behavior within the lifetime of an individual, tempts one to coin intentional explanations. One of Skinner's contributions was to show that if one resists that temptation, one can stay on a sound scientific footing with historical explanations. REFERENCES Amundson, R. (1990). Doctor Dennett and Doctor Pangloss: Perfection and selection in biology and psychology. Behavioral and Brain Sciences, 13, 577-581. Baum, W. M. (1974). Definition in behavioral science: a review of B. B. Wolman's Dictionary of behavioral science. Journal of the Experimental Analysis of Behavior, 22, 445-451. Boakes, R. (1984). From Darwin to behaviourism: Psychology and the minds of animals. Cambridge, England: Cambridge University Press. Chomsky, N. (1959). [Review of Verbal behavior, by B. F. Skinner]. Language, 35, 26-58. Dawkins, R. (1976). The selfish gene. London: Oxford University Press. Day, W. F. (1980). The historical antecedents of contemporary behaviorism. In R. W. Rieber& K. Salzinger(Eds.), Psychology: Theoreticalhistorical perspectives (pp. 203-262). New York: Academic Press. Dennett, D. C. (1978a). Brainstorms: Philosophical essays on mind and psychology. Cambridge, MA: MIT Press. Dennett, D. C. (1978b). Skinner skinned. In Brainstorms: Philosophical essays on mind and psychology (pp. 53-70). Cambridge, MA: MIT Press. Dennett, D. C. (1987a). The intentional stance. Cambridge, MA: MIT Press. Dennett, D. C. (1987b). Skinner placed: A commentary on Place's "Skinner re-skinned." In S. Modgil & C. Modgil (Eds.), B. F. Skinner: Consensus and controversy (pp. 249-252). New York: Falmer Press. Dennett, D. C. (1988). Precis of the intentional stance. Behavioral and Brain Sciences, 11, 495-505. Gish, D. T. (1984). The scientific case for creation. In F. Awbrey & W. M. Thwaites (Eds.), Proceedings of the 63rd Annual Meeting of the Pacific Division, American Association for the Advancement of Science: Evolutionists confront creationists (Vol. I, pp. 25-37). San Francisco: Pacific Division of AAAS. James, W. (1974). Pragmatism and four essays from The meaning of truth. New \brk: New American Library. (Reprint of editions 1907 and 1909) Lee, V. L. (1988). Beyond behaviorism. Hillsdale, NJ: Erlbaum. MacCorquodale, K. (1970). On Chomsky's review of Skinner's Verbal behavior. Journal of the Experimental Analysis of Behavior, 13, 8 3 99. Mach, E. (1960). The science of mechanics: A critical and historical account of its development. Lasalle, IL: Open Court. (Translation of the 9th German ed., 1933) Place, U. (1987). Skinner re-skinned. In S. Modgil & C. Modgil (Eds.), B. F. Skinner: Consensus and controversy (pp. 239-248). New York: Falmer Press. Quine, W. V. (1969). Natural kinds. In Ontological relativity and other essays (pp. 114-138). New York: Columbia University Press. Skinner, B. F. (1953). Science and human behavior. New York: Macmillan. Skinner, B. F. (1969). Contingencies of reinforcement. New York: Appleton-Century-Crofts. Skinner, B. F. (1974). About behaviorism. New York: Knopf. Skinner, B. F. (1990). Can psychology be a science of mind? American Psychologist, 45, 1206-1210. Zuriff, G. E. (1985). Behaviorism: A conceptual reconstruction. New York: Columbia University Press.
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