In the previous two chapters we looked at the nature of mental disorder. We concluded that mental disorder is no myth. Furthermore, even if value judgements are involved in determining whether a condition is a disorder, projects that seek to investigate the causes and natural history of particular conditions can be properly scientific. With the subject matter of psychiatry assured, in this chapter and the next we shall consider the forms of explanation used in psychiatry. I focus particularly on two types of explanation that are frequently found in psychiatry but are less common in many other sciences. This chapter examines what I call “natural-history style explanations”, and Chapter 5 examines how case histories function as explanations. At the outset it is worth noting that these are not the only forms of explanation found in psychiatry. However, I focus on these particular types of explanation because they are characteristic of psychiatry and have been comparatively neglected by philosophers of science.

“Natural-history style” explanations work by invoking “natural kinds”. “Natural kind” is a philosophical term of art, about which I shall have more to say later. For now we can say that paradigmatic examples of natural kinds are biological species and chemical elements. Such kinds are objective: it is a mind-independent fact about the world that lions and tigers are importantly different. They are also theoretically important: distinguishing between lions and tigers is important if one wants to conduct biological research.