The subject of causal explanation in the social sciences has been a recurring thread here (thread). Here are some summary thoughts about social causation.
First, there is such a thing as social causation. Causal realism is a defensible position when it comes to the social world: there are real social relations among social factors (structures, institutions, groups, norms, and salient social characteristics like race or gender). We can give a rigorous interpretation to claims like “racial discrimination causes health disparities in the United States” or “rail networks cause changes in patterns of habitation”.
Second, it is crucial to recognize that causal relations depend on the existence of real social-causal mechanisms linking cause to effect. Discovery of correlations among factors does not constitute the whole meaning of a causal statement. Rather, it is necessary to have a theory of the mechanisms and processes that give rise to the correlation. Moreover, it is defensible to attribute a causal relation to a pair of factors even in the absence of a correlation between them, if we can provide evidence supporting the claim that there are specific mechanisms connecting them. So mechanisms are more fundamental than regularities.
Third, there is a key intellectual obligation that goes along with postulating real social mechanisms: to provide an account of the ontology or substrate within which these mechanisms operate. This I have attempted to provide through the theory of methodological localism (post) — the idea that the causal nexus of the social world is constituted by the behaviors of socially situated and socially constructed individuals. To put the claim in its extreme form, every social mechanism derives from facts about institutional context, the features of the social construction and development of individuals, and the factors governing purposive agency in specific sorts of settings. And different research programs target different aspects of this nexus.
Fourth, the discovery of social mechanisms often requires the formulation of mid-level theories and models of these mechanisms and processes — for example, the theory of free-riders. By mid-level theory I mean essentially the same thing that Robert Merton meant to convey when he introduced the term: an account of the real social processes that take place above the level of isolated individual action but below the level of full theories of whole social systems. Marx’s theory of capitalism illustrates the latter; Jevons’s theory of the individual consumer ss a utility maximizer illustrates the former. Coase’s theory of transaction costs is a good example of a mid-level theory (The Firm, the Market, and the Law): general enough to apply across a wide range of institutional settings, but modest enough in its claim of comprehensiveness to admit of careful empirical investigation. Significantly, the theory of transaction costs has spawned major new developments in the new institutionalism in sociology (Mary Brinton and Victor Nee, eds., The New Institutionalism in Sociology).
And finally, it is important to look at a variety of typical forms of sociological reasoning in detail, in order to see how the postulation and discovery of social mechanisms play into mainstream sociological research. Properly understood, there is no contradiction between the effort to use quantitative tools to chart the empirical outlines of a complex social reality, and the use of theory, comparison, case studies, process-tracing, and other research approaches aimed at uncovering the salient social mechanisms that hold this empirical reality together.