Individual actions make sense in the context, so we have explained their behavior at the micro level. But we can also "calculate" aggregate structural consequences of these actions, and we can thereby reach conclusions about how change in one set of structural conditions led to another set of structural changes through the flow of situated actors choosing their strategies. The powers and resources available to different groups of actors are different and must be carefully assessed by the historian.
This explanatory logic is illustrated in Emmanuel Wallerstein's account of the development of the so-called absolute monarchy in France (The Modern World-System I: Capitalist Agriculture and the Origins of the European World-Economy in the Sixteenth Century, With a New Prologue). Actors choose strategies based on the circumstances, alliances, and opponents that confront them. Actors include: king, lord, peasant, merchant, civil servant, bandit, clergy. Most of these actors also have collective organizations that function as actors at a group level. Economic crisis in the fourteenth and fifteenth centuries led officials of medieval states to broaden and extend their bureaucracies (134). Kings profited from disorder to extend their wealth at the expense of the nobles (135). Kings set more ambitious objectives for their states (135). Kings needed support from nobles and created parliaments. Kings used a variety of strategies to centralize power.
How did kings, who were the managers of the state machinery in the sixteenth century, strengthen themselves? They used four mechanisms: bureaucratization, monopoly of force, creation of legitimacy, and homogenization of the subject population. (136)These actions aggregate into a new set of circumstances, a more effective set of centralized state powers, for the next period of play.
Institutions come into this kind of narrative in two ways. First, they are objective constraints and facts on the ground for the actors, leading actors to adjust their strategies. But second, institutions are built and modified through strategic actions and oppositions of the actors during a period of time. The king wants to strengthen the institutions of tax collection in the provinces; local lords oppose this effort. Each party deploys powers and opportunities to protect its interests. The resultant institutions are different from what either party would have designed.
Where do "causes" come into this kind of narrative? Climate change is a good example. Wallerstein considers the idea that climate change caused the emergence of a new set of institutions of land use (33 ff.). The mechanism is through the actions of the various stakeholders, competing and cooperating to adjust institutions to fit their current needs. Let us say the king is in a situation of greater power than the peasant or the lord. The king largely prevails in institutionalizing a new set of land use practices. One of the causes of the new institution is climate change, working through the strategic actions of the several groups of players. Or: Medieval landowners suffer income loss during a period of economic crisis; they recognize an income opportunity in enclosing public lands for private cultivation; peasants resist using traditional forms of protest; landowners generally have a power advantage and are supported by the state; landowners prevail. In this story, economic crisis causes change of land property relations, mediated by the strategic actions of key actors and groups. (Marx and Brenner tell different versions of this story; link, link.)
A different kind of example comes in at the level of the state. Wallerstein holds that the absolutist state caused the extension of the world trading system. What does he mean by this? He means that new state institutions created new powers and opportunities for several groups of actors, and the net result of these actor's strategies was to bring about a rapid increase in trade and associated military strategies. Again -- a macro cause of a macro outcome, flowing through an analysis of the strategies, interests, and powers of the historically situated actors.
This model of agent-based causal narratives seems to fit well into the methodology of agent-based simulations, with adjustments of the conditions of play from one iteration to the next. We would specify the goals and knowledge possessed by the actors. We would stipulate the institutional "geography" of the playing field. The institutions would define the powers possessed by each actor and the resources available for competition. We would represent alliances, competitions, and outcomes as they develop, noting that there is a stochastic and path-dependent nature to the unfolding of these scenarios.
Essentially the model for explaining social change and stability goes along these lines: actors act according to their interests and psychology. To explain a new outcome we need to identify either:
a structural circumstance or resource that significantly changed the situation of action for one or more groups;Or:
a change in the conditions of agency in the actors themselves -- ideology, religion, new factual theories and beliefs.Either of these changes can then account for a persistent pattern of behavior leading to a new social outcome. This framework of explanation fits well into the ontology of methodological localism and also leaves room for meso-level causal factors.