Philosophers of science sometimes define the idea of a natural kind as "a group of things that share a fundamental set of causal properties." Examples might be "gold," "metal," and "protein molecule." And some philosophers assume that scientific realism means being realist about natural kinds. Do the typical concepts used in the social sciences succeed in identifying a social analog to natural kinds, which might be referred to as "social kinds"? And if not, is it possible to be realist about the social world but anti-realist with respect to "social kinds"?
First, what is involved in being “realist” in connection with the historical and human sciences? It is to assert several independent things: first, that there is the possibility of (fallibly) objective knowledge of social facts; second, that there are “social facts” to be known – that is, there are some mind- or interpretation-independent things that happen and can be the subject of knowledge; and third (questionably), that there are categories of higher-level social entities that “really” exist in the way that some philosophers say that natural kinds exist. It is entirely defensible to be a scientific realist in the social sciences, and I want to support the first two ideas but to argue against the third.
Concepts are of course essential to social knowledge. The heart of social inquiry has to do with coming up with concepts that allow us to better understand social reality: for example, racism, patterns of behavior, free market, class consciousness, ethnic identities. Theory formation in the social sciences largely consists of the task of constructing concepts and categories that capture groups of social phenomena for the purpose of analysis. But even the most successful social concepts do not identify groups of phenomena that could be called a "social kind." High-level social concepts that serve to pick out groups of social phenomena—states, riots, property systems—generally do not refer to causally homogeneous bodies of social phenomena; instead, each of these is composed of individual social formations with their own history and circumstances. There is no uniform causal constitution that underlies all states or riots. The philosophical notions of “family resemblance” and “cluster concepts” serve better to characterize these high-level social concepts than does “natural kind”.
Examples of what might have been thought to be social kinds might include concepts such as these: proletariat, underclass resentment, revolutionary situation, racism; liberal representative states; fascism; feudalism; bureaucratic state. But I hold that these are not kinds in the strong sense that philosophers of the natural sciences have in mind. Rather, they are plastic, variable, opportunistic, individually specific instantiations across a variety of human contexts. We need to be able to identify some topics of interest, so we need language and concepts; but we must avoid reifying the concepts and thinking they refer to some underlying discoverable essence. (Think of how Chuck Tilly conceptualizes riot, rebellion, and resistance in terms of “contentious politics.” Rightly, he avoids the idea that there is one common thing going on in these instances across time, history, and place; his goal is to identify a medium-sized body of causal mechanisms that bundle together in various contexts to give rise to one signature of contention or another.)
The discovery of causal processes is essential to social explanation -- not the discovery of high-level uniform categories of social events or structures. We explain social outcomes best when we can uncover the causal mechanisms that gave rise to them. However, most social ensembles are the result of multiple causal mechanisms, and their natures are not common, simple, or invariant. “States” embody mechanisms of social control. But as Tolstoy said about unhappy families, every state manages its contention in somewhat different ways. So we can’t and shouldn’t expect common causal properties across the class of “states”. And this is directly relevant to the central point here: the "state" is not a social kind, and there is no simple theory that encapsulates its causal properties.
This approach has specific implications for the conduct of the social sciences. For example, political science and the study of different types of states: we can identify common mechanisms, sub-institutions, building blocks, etc., that recur in different political systems. And we can offer causal explanations of specific states in particular historical circumstances -- for example, the Brazilian state in the 1990s. But we cannot produce strong generalizations about “states” or even particular kinds of states -- for example, “developing states”. Or at least, the generalizations we find are weak and exception-laden. Rather, we must build up our explanations from the component mechanisms and institutions found in the particular cases.
So here is a moderate form of scientific realism that is well suited to the nature of the social world: be realist about social mechanisms but not about social kinds. Be realist and empiricist in epistemology: we can arrive at rationally justified beliefs about social mechanisms. And be a skeptic or nominalist about social kinds. There are no macro or molar-level social kinds.