"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."
A contrast to the ideas of emergence, the belief that the sum is greater than the parts '