Historians and social scientists explain at least two sorts of things: (a) those individual human actions that have historical or social significance, such as Stalin’s decision to hold the show trials, Diocletian’s division of the Roman Empire, and the Lord Chief Justice’s attempt to reform the English judicial system; (b) historical and social events and structures (‘large-scale’ social phenomena), such as wars, economic depressions, social customs, the class system, the family, the state, and the crime rate. Philosophical questions arise about explanations of both kinds (a) and (b).
Concerning (b), perhaps the most pressing question is whether explanations of this sort can, ultimately, be understood as merely explanations of a large number of individual human actions, that is, as a complex set of explanations of the first kind, (a).
A causal explanation is an explanation of something in terms of its event-cause(s). Some explanations under (b) appear not to be causal explanations in this sense. There are two ways in which this appears to happen. First, we sometimes seem to explain a social structure or event by giving its function or purpose. This seems to be an explanation in terms of its effects rather than by its causes. For example, it might be claimed that the explanation for a certain social custom in a tribal society is the way in which it contributes to social stability or group solidarity. An explanation of a thing in terms of its effects cannot be a causal explanation of that thing. Second, we sometimes seem to cite social structure as the explanation of something. Whatever a social structure is, it is not itself an event, and since only (it is often said) events can be causes, such a ‘structural’ explanation does not seem to be a causal explanation.
A second question, then, about explanations of kind (b) is whether some of them, at any rate, are genuinely non-causal explanations, or whether functional and/or structural explanations of this sort can be seen as special sorts of causal explanation.
Explanations of kind (a) are a proper subset of explanations of human actions generally. Although some of the discussion of these issues began life as a distinct literature within the philosophy of history, it has now been absorbed into philosophical action theory more generally. Even so, a question that remains is just which proper subset of human actions are the ones of interest to the historical and social sciences: how can we discriminate within the class of human actions between those in which historians or social scientists have a legitimate interest and those outside their purview?
