Psychology has been considered to have an autonomy from the other sciences (especially physical science) in at least two ways: in its subject-matter and in its methods. To say that the subject-matter of psychology is autonomous is to say that psychology deals with entities—properties, relations, states—which 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’ The question of whether psychology as a science is autonomous in either sense is one of the philosophical questions surrounding the (somewhat vague) doctrine of ‘naturalism’: questions concerning 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 17th 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 19th century before starting to become widely accepted, the denial of explanatory autonomy remained a strong force in empiricist philosophy. Hume described his Treatise of Human Nature (1739-40) 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 19th century philosophy, and a question which hovered over the emergence of psychology as an independent discipline (see Reed 1994). In the 20th century, much of the philosophical discussion of the autonomy of psychology has been inspired by the Logical Positivists’ discussions of the UNITY OF.....