Copyright © 1999 Massachusetts Institute of Technology
Psychology has been considered an autonomous science in at least two respects: its subject matter and its methods. To say that its subject matter is autonomous is to say that psychology deals with entities -- properties, relations, states -- that are not dealt with or not wholly explicable in terms of physical (or any other) science. Contrasted with this is the idea that psychology employs a characteristic method of explanation, which is not shared by the other sciences. I shall label the two senses of autonomy "metaphysical autonomy" and "explanatory autonomy."
Whether psychology as a science is autonomous in either sense is one of the philosophical questions surrounding the (somewhat vague) doctrine of "naturalism," which concerns itself with the extent to which the human mind can be brought under the aegis of natural science. In their contemporary form, these questions had their origin in the "new science" of the seventeenth century. Early materialists like Hobbes (1651) and La Mettrie (1748) rejected both explanatory and metaphysical autonomy: Mind is matter in motion, and the mind can be studied by the mathematical methods of the new science just as any matter can. But while materialism (and therefore the denial of metaphysical autonomy) had to wait until the nineteenth century before becoming widely accepted, the denial of explanatory autonomy remained a strong force in empiricist philosophy. HUME described his Treatise of Human Nature (1739-1740) as an "attempt to introduce the experimental method of reasoning into moral subjects" -- where "moral" signifies "human." And subsequent criticism of Hume's views, notably by KANT and Reid, ensured that the question of naturalism -- whether there can be a "science of man" -- was one of the central questions of nineteenth - century philosophy, and a question that hovered over the emergence of psychology as an independent discipline (see Reed 1994).
In the twentieth century, much of the philosophical debate over the autonomy of psychology has been inspired by the logical positivists' discussions of the UNITY OF SCIENCE (see Carnap 1932-1933; Feigl 1981; Oppenheim and Putnam 1958). For the positivists, physical science had a special epistemological and ontological authority: The other sciences (including psychology) must have their claims about the world vindicated by being translated into the language of physics. This extreme REDUCTIONISM did not survive long after the decline of the positivist doctrines which generated it -- and it cannot have helped prevent this decline that no positivist actually succeeded in translating any psychological claims into the language of physics. Thus even though positivism was a major influence on the rise of postwar PHYSICALISM, later physicalists tended to distinguish their metaphysical doctrines from the more extreme positivist claims. J. J. C. Smart (1959), for example, asserted that mental and physical properties are identical, but denied that the psychological language we use to describe these properties can be translated into physical language. This is not yet to concede psychology's explanatory autonomy. That psychology employs a different language does not mean it must employ a different explanatory method. And Smart's identity claim obviously implies the denial of psychology's metaphysical autonomy.
On the other hand, many philosophers think that the possibility of multiple realization forces us to accept the metaphysical autonomy of psychology. A property is multiply realized by underlying physical properties when not all of the instances of that property are instances of the same physical property. This is contrasted with property identity, where a brain property being identical with a mental property, for example, entails that all and only instances of the one property are instances of the other. Hilary Putnam (1975) argued influentially that there are good reasons for thinking that psychological properties are multiply realized by physical properties, on the grounds that psychological properties are functional properties of organisms -- properties identified by the causal role they play in the organism's psychological organization (see FUNCTIONALISM).
This kind of functionalist approach implies a certain degree of metaphysical autonomy: Because psychological properties are multiply realized, it seems that they cannot be identical with physical properties of the brain (but contrast Lewis 1994). It does not, however, imply a Cartesian dualist account of the mind, because all these properties are properties of physical objects, and the physical still has a certain ontological priority, sometimes expressed by saying that everything supervenes on the physical (see SUPERVENIENCE and MIND-BODY PROBLEM). The picture that emerges is a "layered world": The properties of macroscopic objects are multiply realized by more microscopic properties, eventually arriving at the properties which are the subject matter of fundamental physics (see Fodor 1974; Owens 1989).
With the exception of some who hold to ELIMINATIVE MATERIALISM, who see the metaphysical autonomy of commonsense (or "folk") psychological categories as a reason for rejecting the entities psychology talks about, the "layered world" picture is a popular account of the relationship between the subject matters of the various sciences. But what impact does this picture have on the question of the explanatory autonomy of psychology? Here matters become a little complex. The "layered world" picture does suggest that the theories of the different levels of nature can be relatively independent. There is also room for different styles of explanation. Robert Cummins (1983) argues that psychological explanation does not conform to the "covering law" pattern of explanation employed in the physical sciences (where to explain a phenomenon is to show it to be an instance of a law of nature). And some influential views of the nature of computational psychology treat it as involving three different levels of EXPLANATION (see Marr 1982). But in general, nothing in the "layered world" picture prevents psychology from having a properly scientific status; it is still the subject matter (psychological properties and relations) of psychology that ultimately sets it apart from physics and the other sciences. In short, the "layered world" conception holds that psychological explanation has its autonomy in the sense that it does not need to be reduced to physical explanation, but nonetheless it is properly scientific.
This view can be contrasted with Davidson's (1970) view that there are features of our everyday psychological explanations that prevent these explanations from ever becoming scientific. Davidson argues that psychological explanations attributing PROPOSITIONAL ATTITUDES are governed by normative principles: In ascribing a propositional attitude to a person, we aim to make that person's thought and action as reasonable as possible (for related views, see McDowell 1985; Child 1994). In natural science, no comparable normative principles are employed. It is this dependence on the "constitutive ideal of rationality" that prevents a psychology purporting to deal with the propositional attitudes from ever becoming scientific -- in the sense that physics is scientific. According to Davidson, decision theory is an attempt to systematize ordinary explanations of actions in terms of belief and desire, by employing quantitative measures of degrees of belief and desire. But because of the irreducibly normative element involved in propositional attitude explanation, decision theory can never be a natural science (for more on this subject, see Davidson 1995). Where the "layered world" picture typically combines a defense of metaphysical autonomy with an acceptance of the properly scientific (or potentially scientific) nature of all psychological explanation, Davidson's ANOMALOUS MONISM combines strong explanatory autonomy with an identity theory of mental and physical events.
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