I believe that hypotheses, theories, and explanations in the social sciences need to be subject to the requirement of microfoundationalism. This requirement can be understood in a weak and a strong version, and sometimes people understand the idea as a requirement of reductionism. In brief, I defend the position in a weak form that does not imply a reductionist theory of social explanation. Recent discussions with Julie Zahle have led me to sharpen my understanding of the requirement of microfoundations in social theorizing and explanation. Here I would like to clarify my own thinking about the role and scope of the principle of microfoundationalism.
A microfoundation is something like this: an account of the mechanisms at the individual actor level (and perhaps at levels intermediate between actors and the current level -- e.g. institutions) that work to create the structural and causal properties that we observe at the meso or macro level. A fully specified microfoundational account of a meso-level feature consists of an account that traces out (1) the features of the actors and (2) the characteristics of the action environment (including norms and institutions) which jointly lead to (3) the social pattern or causal power we are interested in. A microfoundation specifies the individual-level mechanisms that lead to the macro- or meso-level social fact. This is the kind of account that Thomas Schelling illustrates so well in Micromotives and Macrobehavior.
My thinking about the need for microfoundations has changed over the years from a more narrow requirement ("we need to have a pretty good idea of what the individual-level mechanisms are for a macro-property") to a less restrictive requirement ("we need to have reason to believe that there are individual-level mechanisms for a macro-property"). In The Scientific Marx I liked the idea of “aggregative explanations”, which are really explanations that move from features of individual actors and their interactions, to derivations about social and collective behavior. In Varieties of Social ExplanationI relaxed the idea along these lines:
This doctrine [of microfoundationalism] may be put in both a weak and a strong version. Weakly social explanations must be compatible with the existence of microfoundations of the postulated social regularities, which may, however, be entirely unknown. More strongly social explanations must be explicitly grounded on an account of the microfoundations that produce them. I will argue for an intermediate form—that we must have at least an approximate idea of the underlying mechanisms at the individual level if we are to have a credible hypothesis about explanatory social regularities at all, A putative explanation couched in terms of high-level social factors whose underlying individual-level mechanisms are entirely unknown is no explanation at all. (kl 4746)
My adherence to microfoundationalism today is a little bit weaker still. I now advocate a version of microfoundationalism that specifies only that we must be confident (an epistemic concept) that such micro-to-macro relations exist. We must be confident there are such mechanisms but not obliged to specify them. (I also hold that the best ground for having that confidence is being able to gesture plausibly towards roughly how they might work.) Another way to put it is this requirement: "No magical thinking!" That is, we exclude explanations that would only be possible if we assumed action at a distance, blocks of wood that have complicated mental lives, or intelligent beings with infinite computational faculties. A convincing way of discrediting a meso-level assertion is to give an argument that it is unlikely that real human agents would in fact act in ways that lead to this meso-level situation. (Example: Chinese planners who created the collective farming system in the Great Leap Forward assumed that collective farms would be highly productive because a "new socialist man" would emerge. This was unlikely, and therefore the individual behavior to be expected on collective farms would lead to "easy riding" and low productivity.)
Here is an effort to simplify these issues into a series of assertions:
- All social forces, powers, structures, processes, and laws (social features) are ultimately constituted by mechanisms at the level of individual actors. (ontological principle)
- When we assert the reality or causal powers of a social entity, we need to be confident that there are microfoundations that cause this social entity to have the properties we attribute to it. (microfoundations principle)
- A description of the microfoundations of a social entity S is an account of the circumstances and individual mechanisms that bring about patterns of individual activity resulting in the properties of S.
- Strong version: we must provide a credible statement of the microfoundations.
- Intermediate version: we must have a back-of-envelope sketch of possible microfoundations.
- Weak version: we must have confidence that there are microfoundations, but we don’t have to have any specific ideas about what they are.
- A "vertical" social explanation of the features of a social entity S is a derivation of S from facts about the individual level. This is equivalent to providing a specification of the microfoundations of S; a derivation of the properties of S from a model of the action situation of the individuals involved; an agent-based model. This is what JZ calls an individualist explanation.
- A "horizontal" social explanation is one in which we explain a social entity or structure S by referring to the causal properties of other meso-level entities and conditions. This is what we call a meso-level explanation. (The diagram above illustrates these ideas.)
- Horizontal explanations are likewise subject to the microfoundations requirement 2: the entities and powers postulated need to be such that we have good reason to believe that there are microfoundations available for these entities and properties. (Epistemic requirement)
- Or slightly stronger: we need to be able to offer at least a plausible sketch of the microfoundations / individual-level mechanisms that would support the postulated entities. (Epistemic+ requirement)
- Providing or hypothesizing about microfoundations always involves modeling the behaviors and interactions of individuals; so it requires assuming a theory of the actor. So when we try to specify or hypothesize about microfoundations for something we are obliged to make use of some theory of the actor.
- Traditional theories of the actor are generally too abstract and too committed to a rational-choice model.
- Social scientists will be better able to hypothesize microfoundations when they have richer theories of the actor. (heuristic principle)
So the ontological principle is simply that social entities are wholly fixed by the properties and dynamics of the actions of the actors that constitute them. The requirement of microfoundations simply reproduces the ontological principle, ruling out ontologically impossible relations among social entities. The requirement of microfoundations is not a requirement on what an explanation needs to look like; rather, it is a requirement about certain beliefs we need to be justified in accepting when we advance a claim about social entities. It is what JZ calls a “confirmation” requirement (or perhaps better, a justificatory requirement). A better theory of the actor supports the discovery of microfoundations for social assertions. Further, it provides a richer "sociological imagination" for macro- and meso-level sociologists. So the requirement of microfoundations and the recommendation that social scientists seek out better theories of the actor are also valuable as heuristics for social research: they provide intellectual resources that help social researchers decide where to look for explanatory links, and what kinds of mechanisms might turn out to be relevant.