A recent post at Understanding Society gives a very nice introduction to methodological individualism (MI) in the social sciences (see also this introduction at the Stanford Encyclopedia of Philosophy, also linked in the post). The heart of the argument is about what sorts of causal arguments and explanations MI does and does not preclude:

…to concede that x’s are composed of y’s does not entail the need for any kind of reductionism from x to y. And this extends to the idea of explanatory reduction as well. So methodological individualism does not create valid limits on the structure of social explanations, and meso-level explanations are not excluded.

This point has broader implications for political science. To say that social entities are composed of individuals, and that political outcomes are the results of individual actions, does not entail that we must to look for individual-level evidence or explanations for these outcomes. This is related to some comments I’ve made here on  Microfoundations for Political Science, which brings a skeptical perspective to the quest for microfoundations for every political science research topic, as if the research topics can never be properly understood unless we gin up some microfoundations (or microdata, or whatever) to test them.

One somewhat related observation. When I introduce MI to graduate students as a framework for doing comparative politics, I go back to Jeremy Bentham’s An Introduction to the Principles of Morals and Legislation:

The interest of the community is one of the most general expressions that can occur in the phraseology of morals: no wonder that the meaning of it is often lost. When it has a meaning, it is this. The community is a fictitious body, composed of the individual persons who are considered as constituting as it were its members. The interest of the community then is, what?—the sum of the interests of the several members who compose it.

This is not methodological individualism as Weber meant it. But the links should be apparent. It introduces the ontological position on collectives which is so critical for MI; it also reveals the link between MI and the various traditions that are lumped together as “rational choice theory.”