This book relies on a specific view about explanation in the social sciences. Although not primarily a work of philosophy of social science, it draws upon and advocates certain methodological ideas about how to explain social phenomena. In the first three chapters, these ideas are set out explicitly. In the rest of the book they mostly form part of the implicit background, although from time to time, notably in the Conclusion, they return to the center of the stage.

I argue that all explanation is causal. To explain a phenomenon (an explanandum) is to cite an earlier phenomenon (the explanans) that caused it. When advocating causal explanation, I do not intend to exclude the possibility of intentional explanation of behavior. Intentions can serve as causes. A particular variety of intentional explanation is rational-choice explanation, which will be extensively discussed in later chapters. Many intentional explanations, however, rest on the assumption that agents are, in one way or another, irrational. In itself, irrationality is just a negative or residual idea, everything that is not rational. For the idea to have any explanatory purchase, we need to appeal to specific forms of irrationality with specific implications for behavior. In Chapter 14, for instance, I enumerate and illustrate eleven mechanisms that can generate irrational behavior.

Sometimes, scientists explain phenomena by their consequences rather than by their causes. They might say, for instance, that blood feuds are explained by the fact that they keep populations down at sustainable levels. This might seem a metaphysical impossibility: how can the existence or occurrence of something at one point in time be explained by something that has not yet come into existence? As we shall see in Chapter 11, the problem can be restated so as to make explanation by consequences a meaningful concept. In the biological sciences, evolutionary explanation offers an example. In the social sciences, however, successful instances of such explanations are few and far between. The blood-feud example is definitely not one of them.