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This chapter takes a specific objective: to identify and analyze the philosophical and conceptual conditions that are involved in postulating causal relations among meso-historical entities, structures, and processes. What is the nature of the causal relations among structures and entities that make up the social world? What sorts of mechanisms are available to substantiate causal claims such as “population pressure causes technological innovation,” “sharecropping causes technological stagnation in agriculture,” or “limited transport and communication technology causes infeudation of political power”? What are the causal mechanisms through which social practices, ideologies and systems of social belief are transmitted? How are structures and practices instantiated or embodied, and how are they transmitted and maintained? Do causal claims need to be generalizable? How do historians identify and justify causal hypotheses?

The general answers I offer flow from a very simple perspective that was developed in the preceding two chapters. Social structures and institutions have causal properties and effects that play an important role within historical change (the social causation thesis). They exercise their causal powers through their influence on individual actions, beliefs, values, and choices (the microfoundations thesis). Structures are themselves influenced by individuals, so social causation and agency represent an ongoing iterative process (the agency-structure thesis). And hypotheses concerning social and historical causation can be rigorously formulated, criticized, and defended using a variety of tools: case-study methodology, comparative study, statistical study, and application of social theory.

Historians and historical sociologists are commonly interested in providing causal explanations of large historical outcomes: revolutions, social contention, state formation, the spread of religious ideas, and many other sorts of phenomena. Often these research efforts depend on the Millian idea, “same cause, same effect,” which unfolds into a theory of causal inquiry based on methodical comparison of cases (Goldstone, 2003; Goldthorpe, 1997; Kiser and Hechter, 1991; Lichbach and Zuckerman, 1997; Mahoney, 1999; Mahoney and Rueschemeyer, 2003; Ragin, 1987, 1998; Skocpol and Somers, 1979). This approach is contrasted to the quantitative methodologies of causal analysis that depend on discovery of correlations among variables in large datasets.

Here I will make the case that the discovery of historically specific causal mechanisms is feasible, rigorous, and explanatory. Second, it will be argued that it is possible to provide a rigorous interpretation of the “metaphysics” of social causal mechanisms, working through the structured circumstances of choice of socially constructed actors. This approach makes good use of the new institutionalism, in that the new institutionalism emphasizes the causal powers and differentiating influences of specific institutional arrangements. This approach provides an alternative to a narrowly empiricist search for governing social laws or generalizations as the basis for social explanations. But equally it represents an alternative to idiographic narrative. The chapter will attempt to establish the coherence and plausibility of the social-mechanism approach to research and explanation in historical sociology.

5.1 A Range of Causal Questions

Consider a range of causal questions and hypotheses that have arisen within historical and comparative sociology.

  • What causes ethnic violence (Horowitz, 1985)?

  • What caused ethnic violence in Rwanda?

  • What caused twentieth-century revolutions (Wolf, 1969)?

  • What caused the Nicaraguan revolution?

  • Why did revolution unfold as it did in the Canton Delta in 1911 (Hsieh, 1974)?

  • What factors explain the East Asian economic miracle (Vogel, 1991)?

  • Why was the political party of labor more successful in the UK than the US (Przeworski, 1985)?

  • Why is infant mortality significantly lower in Sri Lanka than Brazil or Egypt (Drèze and Sen, 1989, 1995)?

  • Why do millenarian cults occur in the post-colonial world (Adas, 1979)?

  • Why was agricultural technology stagnant in late imperial China (Elvin, 1973)?

  • Why do social tastes and styles change as they do (Lieberson, 2000)?

  • Why did the New England Patriots win the 2003 Super Bowl (Lieberson, 1997)?

  • Why did the political culture of corporations remain powerful among French workers in the nineteenth century (Sewell, 1980)?

  • Why did the heavy wheeled plough diffuse in the geographical pattern that it did in medieval France (Bloch, 1966)?

And here are some typical historical causal claims, both singular and general:

  • Population increase causes technological innovation (Boserup, 1981).

  • A free press within an electoral democracy causes a low incidence of famine (Drèze and Sen, 1989, 1991).

  • The fiscal system of the ancien régime caused the collapse of the French monarchy (Soboul, 1989).

  • Transport systems cause patterns of commerce and habitation (Skinner, 1964–1965).

  • New market conditions cause changes in systems of norms (Popkin, 1979).

  • A new irrigation system causes changes in family organization (Pasternak, 1978).

  • Concentrated urban demand causes development of an infrastructure to support a flow of timber and grain into the metropolis (Cronon, 1991).

  • The principal-agent problem represented by cattle herding in Kenya causes the emergence of the practice of bridewealth (Ensminger, 1992).

  • Citizens’ shared sense of justice causes stability of existing legal system (Rawls, 1993).

  • Availability of large financial resources and a favorable regulatory/governmental environment in the city of Chicago were necessary conditions for the development of a regional electricity system in Chicago in the 1910s and 1020s (Hughes, 1983).

We can learn a great deal about causal inquiry by reflecting briefly on a number of these examples. There is a common thread among these examples, in that each question directs inquiry towards the question, “What are the causal conditions that give rise to a given social or historical outcome?” But there are a number of important differences among these examples as well. Some are about a category of outcome (“twentieth-century revolution” or “ethnic violence”), whereas others are about a historically specific outcome (the Nicaraguan revolution, the Rwandan genocide, the 2003 Super Bowl). Some are about large and publicly salient events, structures, and mentalités (states, revolutions, political cultures); others are about small-scale and unnoticed social characteristics (the frequency of first names).

These examples illustrate a number of different patterns of causal relations among social entities, structures, and outcomes. We have—

  • change in structure causes change in behavior

  • change in structure causes change in norms

  • change in structure causes change in structure

  • persistence of norms causes persistence of structure

  • persistence of structure causes persistence of norms

  • change of material resources leads to change of norms and practices

  • change in population or density causes change in structure

  • change in population or density causes change in process (e.g. technological innovation)

This chapter focuses on the idea that social causation is constituted by concrete causal mechanisms linking one set of social circumstances to another, and that historical and social inquiry into social causation needs to be designed in recognition of this fact. Two central conclusions are key: that it is possible to provide “theories at the middle range” of some causal mechanisms that occur in multiple social and historical settings—which can be used to explain similarities and contrasts among broadly comparable historical outcomes; and that it is possible to identify concrete and historically specific causal mechanisms at work in large sociological processes (single-case causal analysis)—which then provides a basis for explaining the large historical outcome or condition.

Let us expand upon several of the causal stories offered above to get a better idea of the nature of these causal hypotheses.

A new irrigation system causes changes in family organization. Rural society in pre-1930 Taiwan featured a “joint-family” system, in which a parent and married sons would continue to live together and farm their holdings together rather than dividing into two or more nuclear families. After the 1930, however, a trend toward divided families began and has continued until the present. Why did this change in family structure occur? It is often believed that family structure is a deeply idiosyncratic feature of a given culture. But Burton Pasternak attempts to show that the joint-family system in the Taiwan rice economy is a prudent arrangement for the organization of farm labor, given the uncertainties of rainfall (Pasternak, 1978). Pasternak offers this model of the domestic economy. Rice must be transplanted within 20 days and can only be transplanted if there is enough water. The model family contains two married brothers (A and B) and A’s son. The family owns 2 ha (5 acres) and two water buffalo. As a joint family the unit can manage field preparation and transplanting in 19–22 days. As two divided units A and his son can manage 1 ha in 17–20 days, but B needs 22–25 days. This means that his rice crop will often fail. If there are fewer than 10 days of rain, both families will lose the crop. If there are fewer than 15 days of rain, A will survive and B will not. In times of water crisis, the joint family has enough labor to plant a crisis crop (sweet potatoes), but the divided families do not. Therefore, if cropping depends on rainfall, the joint family is substantially more secure. After the Japanese removed this uncertainty by creating a large irrigation system in the 1930s, the joint-family practice began to disappear. With irrigation the water supplies are much more secure, and crisis is therefore less likely. Under these circumstances there are incentives for dividing the family and fewer economic reasons not to do so. Once the imperative to protect against catastrophic crop failure due to inadequate labor supply was diminished, the normal frictions of social life (between sisters-in-law, for example) led to a division of families. Thus Pasternak explains the change in family structure as the effect of changing circumstances of the rural economy—the availability of reliable irrigation water. The mechanism postulated is the adaptive, purposive behavior of the actors involved.

A free press within an electoral democracy causes a low incidence of famine. Drèze and Sen offer a careful study of India’s experience of hunger and famine since Independence (Drèze and Sen, 1989). Sen had previously offered a careful study of the great Bengal famine of 1942 (Sen, 1981). In their study of post-independence India they find the interesting fact that India, little less poor than it was in the 1940s, had nonetheless not experienced another widespread famine since independence. Why was this? They offer a simple theory along these lines: India was an electoral democracy in which the Congress party needed to compete for electoral support on a regular basis. India also possessed a vigorous free press with numerous newspapers and a tradition of prompt and unencumbered news investigation. Occurrence of famine anywhere in India would be a very significant failure for the governing party. This combination of circumstances gave the government, and the party in power, a large political incentive to implement institutions that would prevent the occurrence of famine: early warning systems, stockpiles of grain, and a responsive government emergency system. These mechanisms are effective in preventing famine. Governments therefore pursued their political interests by adopting these mechanisms; and the absence of famine during the period is the effect of this adoption. Sen and Drèze note the important contrast to the experience of China during the Great Leap Forward: information indicating the existence of widespread hunger and impending famine was available to the central government in the fall of 1959, but the government took no effective emergency measures for a full year. There was little public notice of famine outside of affected areas, and the government had little to fear from the public because its hold on power did not depend on electoral processes. (That is: in a broadly similar material and population setting, a polity without electoral politics and a free press does suffer from a major famine.)

Citizens’ shared sense of justice causes stability of existing legal system. Barrington Moore points out that a system of law cannot easily depend exclusively on fear of punishment (Moore, 1978). The supervisory power of the state is limited. Citizens, on the whole, comply with the law in a voluntary fashion. What are the factors that serve to render a legal system stable? Moore points to a social fact: when there is a widespread belief that the legal system is fair and just, individuals will have a motivation to comply. Likewise, when citizens believe that the system of law is unjust and unfair, or is used for the benefit of some over others, they will have a motivation to resist. In other words, the social fact that “most citizens regard the existing legal system as fair” causes the stability of the existing legal system. Symmetrically, the social fact that “many citizens regard the legal system as unfair” has the potential to cause destabilization of the legal system—the central point of Moore’s argument.

5.2 Causal Realism

These examples show that causal explanations are ubiquitous in meso-history. What is involved in asserting a causal relation among historical factors—for example, that “a free press” causes “lower incidence of famine”? Many historical explanations depend on a position that we can describe as “causal realism”. The central tenet of causal realism is a thesis about the reality of causal mechanisms or causal powers. Causal realists maintain that we can only assert that there is a causal relationship between X and Y if we can offer a credible hypothesis about the sort of underlying mechanism that might connect X to the occurrence of Y. The sociologist Mats Ekström puts the view this way: “the essence of causal analysis is… the elucidation of the processes that generate the objects, events, and actions we seek to explain” (Ekstrom, 1992, p. 115). Authors who have urged the centrality of causal mechanisms for both explanatory and ontological purposes include Nancy Cartwright (1989), Jon Elster (2007), Rom Harré and Edward H. Madden (1975), and Wesley Salmon (1984). (Hedstrom and Swedberg’s collection on mechanisms in the social sciences is a key source on this topic; Hedström and Swedberg, 1998.)

Aage Sørensen summarizes a causal realist position for sociology in these terms: “Sociological ideas are best reintroduced into quantitative sociological research by focusing on specifying the mechanisms by which change is brought about in social processes” (Sørensen, 1998, p. 264). Central to an adequate explanatory theory is the specification of the mechanism that is hypothesized to underlie a given set of observations. “Developing theoretical ideas about social processes is to specify some concept of what brings about a certain outcome—a change in political regimes, a new job, an increase in corporate performance. … The development of the conceptualization of change amounts to proposing a mechanism for a social process” (pp. 239–240). Sørensen makes the critical point that one cannot select a statistical model for analysis of a set of data without first asking the question, what in the nature of the mechanisms we wish to postulate to link the influences of some variables with others? It is necessary to have a hypothesis of the mechanisms that link the variables before we can arrive at a justified estimate of the relative importance of the causal variables in bringing about the outcome.

A particularly important recent effort to make use of causal mechanisms as a foundation for social research is found within the literature on social contention—the occurrence of medium- and large-scale episodes of contention in a variety of social settings. Charles Tilly, Doug McAdam, and Sidney Tarrow have applied framework of causal mechanisms with a great deal of rigor in Dynamics of Contention (McAdam et al., 2001) and a volume of associated research. They provide a simple definition of mechanisms: “a delimited class of events that alter relations among specified sets of elements in identical or closely similar ways over a variety of situations” (McAdam et al., 2001, p. 24). And processes are concatenations of mechanisms: “regular sequences of such mechanisms that produce similar (generally more complex and contingent) transformations of these elements” (p. 24). “We employ mechanisms and processes as our workhorses of explanation, episodes as our workhorses of description. We therefore make a bet on how the social world works: that big structures and sequences never repeat themselves, but result from differing combinations and sequences of mechanisms with very general scope” (p. 30). They summarize their theoretical ambitions concisely: “Our aim is not to construct general models of revolution, democratization, or social movements, much less of all political contention whenever and wherever it occurs. On the contrary, we aim to identify crucial causal mechanisms that recur in a wide variety of contention, but produce different aggregate outcomes depending on the initial conditions, combinations, and sequences in which they occur” (p. 37).

What is a causal mechanism? Consider this formulation:

A causal mechanism is (i) a particular configuration of conditions and processes that (ii) always or normally leads from one set of conditions to an outcome (iii) through the properties and powers of the events and entities in the domain of concern.Footnote 1

Mechanisms bring about specific effects based on the properties of the substrate of processes and events in this domain. For example, “over-grazing of the commons” is a mechanism of resource depletion in the context of a non-regulated community of users (Hardin, 1968). We can reconstruct precisely why this would be true for rationally self-interested actors in the presence of a public good: rational agents use more of the “free” public resource to increase their own private consumption, and this behavior aggregates to over-use of the public resource. This is how we specify condition (iii) for the overgrazing mechanism. Further, it is the case that, whenever the conditions of the mechanism are satisfied, the result regularly ensues; in any case where the dominant motive for agents is rational self-interest, we can expect that a common resource will be over-used.

So we do not need to postulate “laws of society” in order to see how social causation might work. Instead, we can directly identify the features of purposive action within given structures that make the mechanism work. Human actions and refrainings are the “stuff” of social causation, and features of human agency underwrite the “necessity” of social mechanisms. So we can properly understand a claim for social causation along these lines: “C causes E” means “there is a set of causal mechanisms working through features of structured agency that convey circumstances including C to circumstances including E.” It follows from this analysis that mechanisms implicate regularities. But these regularities are low-level and may not be observable in macro-level social behavior (for example, because of the mixing of several causal processes and the possibility of countervailing mechanisms in play). So they do not serve to play the role of a set of governing laws of society, analogous to laws of nature.

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-riding. These theories and models are “theories of the middle range” in much the sense that Robert Merton meant to convey when he introduced the term (Merton, 1963): accounts 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 as a utility maximizer illustrates the former. Coase’s theory of transaction costs is a good example of a mid-level theory (Coase, 1988): general enough to apply across a wide range of institutional settings, but restricted 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.

So this provides an answer to the fundamental question: explaining a social outcome or pattern involves providing an account of the social-causal mechanisms that typically bring it about, or brought it about in specific circumstances. But what is the nature of the substrate of social causation? What do social mechanisms consist of? What makes them operate in the patterned and regular ways that we hypothesize for them?

The general nature of the mechanisms that underlie sociological causation has been very much the subject of debate. Two broad approaches may be identified: agent-based perspectives and social-influence theories. The former follow the strategy of aggregating the results of individual-level choices into macro-level outcomes; the latter attempt to identify the factors that work behind the backs of agents to influence their choices. Thomas Schelling’s apt title Micromotives and Macrobehavior captures the logic of the former approach, and his work profoundly illustrates the sometimes highly unpredictable results of the interactions of locally rational behavior (Schelling, 1978). Jon Elster has also shed light on the ways in which the tools of rational choice theory support the construction of large-scale sociological explanations (Elster, 1989b). The second approach, the social-influence approach, attempts to identify socially salient influences such as race, gender, educational status, and to provide detailed accounts of how these factors influence or constrain individual trajectories—thereby affecting sociological outcomes. These should not be understood as being contradictory approaches; rather, they each direct explanatory inquiry at different parts of the same nexus of socially situated agency. The first set of approaches pays primary attention to the motives and reasonings of agents within a given set of constraints; while the second set gives more attention to the broad social factors that influence individual agency.

How do social mechanisms work? The basics are fairly clear: individuals have goals, values, and beliefs, they exist within social and natural constraints, and their actions bring about a variety of social outcomes. But how do features of “agents within structures” bring about social outcomes? We can give a somewhat more detailed analysis of some of the ways that social facts might cause other social facts by surveying a wide sample of causal explanations from history and the social sciences. This approach leads to an open-ended list of kinds of social mechanisms.

  1. 1.

    Rational-intentional mechanisms. Why do empires establish a policy of rotating senior military officials? Because emperors want to avoid the creation of warlords.

  2. 2.

    Imitation mechanisms. Why did the no-huddle offense become so common in the National Football League in the 1980s? Because it was successful for a few teams, and others copied the offense in the hope that they too would win more games.

  3. 3.

    Conspiracy mechanisms (covert strategems of the powerful). Why did the United States move away from passenger railroads as the primary form of intercity transportation? Because powerful actors took political actions to assure that private automobiles would be encouraged as the primary form of transport.

  4. 4.

    Aggregative mechanisms (aggregate consequences of individual-level strategies). Why does technological innovation occur continuously within a market-based society? Because each firm is constantly looking for lower-cost and higher-value-added methods of manufacturing, and these individual efforts aggregate to an industry trend towards innovations in products and technologies.

  5. 5.

    Mentality mechanisms (behavior is changed by changing beliefs and attitudes). Why were so many Quaker men conscientious objectors at great personal cost during World War II? Because their religious beliefs categorically rejected the violence in war and they refused to participate in this immoral activity.

  6. 6.

    Social network mechanisms (information and norms proliferate through concrete sets of social relationships among individuals). Why was the Soviet military system less adaptive in combat than the Israeli military system? Because information flow among officers and troops was more rapid and more bidirectional in the latter than the former.

  7. 7.

    Evolutionary mechanisms. Why does the level of firm efficiency tend to rise over time? Because the net efficiency of a firm is the product of many small factors. These small factors sometimes change, with an effect on the efficiency of the firm. Low efficiency firms tend ultimately to lose market share and decline into bankruptcy. Surviving firms will have features that produce higher efficiency.

  8. 8.

    Filtering mechanisms. Why are passengers on commercial aircraft better educated than the general population? Because most airline passengers are business travelers, and high-level and mid-level business employees tend to have a higher level of education than the general population.

  9. 9.

    Critical mass mechanisms. A new social networking site experiences slow growth for the first 18 months of operation until it reaches N users; it then takes off with rapid growth for the next 18 months. We attempt to explain this change by arguing that N is a critical mass of users, stimulating much more rapid growth in the future.

  10. 10.

    Path-dependency mechanisms. Why do we still use the very inefficient QWERTY keyboard arrangement that was devised in 1874? Because this arrangement, designed to keep typists from typing faster than the mechanical keyboard would permit, was so deeply embodied in the typing skills of a large population and the existing typewriter inventory by 1940 that no other keyboard arrangement could be introduced without incurring massive marketing and training costs.

This is not intended to be an exhaustive list of types of social causation, and there is some overlap among these types. The first four examples fall roughly into the broad category of agent-centered explanations; the next three examples illustrate the social-influence model; and the final three examples illustrate “system-level” features of the environment of social change (selective filtering of events, the mathematics of critical mass, and the momentum of prior social choices). There are no doubt another dozen examples of explanatory schemata that could be adduced as well. What this list illustrates, however, is that there are a variety of ways, both direct and indirect, through which social causation can be conveyed from one set of social facts to another. They all involve the same basic ontology of social causation—agents acting within structures leading to social outcomes—but the nature of the pathway from cause to effect is different in the various types.

This approach places central focus on the idea of a causal mechanism: to identify a causal relation between two kinds of events or conditions, we need to identify the typical causal mechanisms through which the first kind brings about the second kind. What, though, is the nature of the relations that constitute causal mechanisms among social phenomena?

On the methodological-localist approach, the causal capacities of social entities are to be explained in terms of the structuring of preferences, worldviews, information, incentives, and opportunities for agents. The causal powers or capacities of a social entity inhere in its power to affect individuals’ behavior through incentives, preference-formation, belief-acquisition, or powers and opportunities. The micro-mechanism that conveys cause to effect is supplied by an account of the actions of agents with specific goals, beliefs, and powers. Social entities can exert their influence, then, in several possible ways.

  • They can alter the incentives presented to individuals.

  • They can alter the preferences of individuals.

  • They can alter the beliefs of individuals. (Constraints on knowledge; ideology )

  • They can alter the powers or opportunities available to individuals. (Social structures and institutions)

  • They can confer power on some agents relative to other agents.

Social causal ascriptions thus depend on common characteristics of agents (e.g., the central axioms of rational choice theory, or other theories of practical cognition and choice). I would assert, then, that the most basic foundations for social causal explanation are stories about the characteristics of typical human agents within specific institutional settings. The causal powers of a particular social institution—a conscription system, a revenue system, a system of democratic legislation—derive from the incentives, powers, and knowledge that these institutions provide for participants. Social entities thus possess causal powers in a derivative sense: they possess characteristics that affect individuals’ behavior in simple, widespread ways. Given features of the common constitution and circumstances of individuals, such alterations at the social level produce regularities of behavior at the individual level that eventuate in new social circumstances.

Emphasis on causal mechanisms for adequate social explanation has several beneficial effects on sociological method. It takes us away from easy reliance on uncritical statistical models. But it also may take us away from excessive emphasis on large-scale classification of events into revolutions, democracies, or religions, and toward more specific analysis of the processes and features that serve to discriminate among instances of large social categories. Charles Tilly emphasizes this point in his arguments for causal narratives in comparative sociology (Tilly, 1995). He writes, “I am arguing that regularities in political life are very broad, indeed transhistorical, but do not operate in the form of recurrent structures and processes at a large scale. They consist of recurrent causes which in different circumstances and sequences compound into highly variable but nonetheless explicable effects” (Tilly, 1995, p. 1601).

We do a poor job of understanding industrial strikes if we simply collect a thousand instances and perform statistical analysis on the features we’ve measured against the outcome variables. We do a much better job of understanding them if we put together a set of theories about the features of structure and agency through which a strike emerges and through which individuals make decisions about participation—the mechanisms that commonly arise in the social processes of industrial contention. Analysis of the common “agent/structure” factors that are relevant to mobilization will permit us to understand individual instances of mobilization, explain the soft regularities that we discover, and account for the negative instances as well.

5.3 Examples of Social Mechanisms

It is useful at this point to offer a deliberately heterogeneous list of social processes that have served as hypotheses about social mechanisms in the social sciences:

  • Freerider problems undermining effective collective action (Olson, 1965)

  • Logic of prisoners’ dilemma explaining defection of Catholic villages in colonial Vietnam (Popkin, 1979)

  • The market mechanism as an explanation of price equilibria among independent producers, traders, and consumers

  • Sørensen’s model of the mechanisms of career and income (Sørensen, 2001)

  • Practical cognition errors underlying common forms of social action (Kahneman et al., 1982)

  • Political entrepreneurship as a mechanism leading to ethnic conflict (Kohli, 1990)

  • The pre-famine mechanism (Sen, 1981)

  • “Stereotype threat” as a mechanism underlying black-white performance gap (Steele and Aronson, 1995)

  • The “ratchet effect” as a mechanism of change in social tastes (Lieberson, 2000)

  • Pattern of recruitment into a labor union as a mechanism of union radicalism (Kimeldorf, 1988)

Transport systems have the causal capacity to influence patterns of settlement; settlements arise and grow at hubs of the transport system. Why so? It is not a brute fact , representing a bare correlation of the two factors. Instead, it is the understandable result of a fuller description of the way that commerce and settlement interact. Agents have an interest in settling in places where they can market and gain income. The transport system is the structure through which economic activity flows. Proximity to the transport system is economically desirable for agents: they can expect rising density of demand for their services and supply of the things they need. So when a new transport possibility emerges—extension of a rail line, steamer traffic farther up a river, or a new shipping technique that permits cheap transportation to offshore islands—we can expect a new pattern of settlement to emerge as well.

Consider, for a second example, Robert Klitgaard’s treatment of efforts to reduce corruption within the Philippine Bureau of Internal Revenue (Klitgaard, 1988). The key to these reforms was implementation of better means of collecting information about corruption at higher levels of organization and administration. This innovation had a substantial effect on the probability of detection of corrupt officials, which in turn had the effect of deterring corrupt practices. This institutional arrangement has the causal power to reduce corruption because it creates a set of incentives and powers in individuals that lead to anti-corruption behavior.

A third example of social explanation that illustrates the importance of disaggregating social processes onto underlying conjunctions of agency and structure, and the contingency of the social causal processes that result, is found in a large literature on the study of social movements. The literature on “political opportunity structures” emphasizes the contingency of mobilization of social movements depending on the array of opportunities that exist at a given time. Sidney Tarrow summarizes the approach in these terms: “Rather than focus on some supposedly universal cause of collective action, writers in this tradition examine political structures as incentives to the formation of social movements” (Tarrow, 1996a: 41, p. 41). The openness to contingency characteristic of this approach parallels the approach to contentious politics offered in (McAdam et al., 2001).

5.3.1 Transportation as a Large-Scale Historical Factor

Let’s now look at a particularly interesting kind of large structure with important causal properties: transportation. Transportation systems are mundane but pervasive, and they seem to represent a good example of a distributed structure with significant system-wide effects. For example, the settlement patterns of suburban Boston in the early twentieth century depended crucially on the pace and geographical location of the extension of the street car system from downtown Boston into the less developed environs (Warner, 1969). Prior to the extension of the trolley line into Roxbury, Newton, and other Boston suburbs, these areas were home to the affluent and powerful of Boston who could afford to maintain a horse and buggy for transportation. Once the trolley reached these areas, however, it was possible for working families to choose to live in these suburbs and travel to work in Boston by trolley. This created demand for a new kind of housing—smaller, cheaper, and more densely packed. This increase in population density in turn triggered the emergence of a new set of businesses in these areas—green grocers and other suppliers of daily necessities. Warner puts the point this way:

At any given time the arrangements of streets and buildings in a large city represents a temporary compromise among such diverse and often conflicting elements as aspirations for business and home life, the conditions of trade, the supply of labor, and the ability to remake what came before. (Warner, 1969, p. 15)

The theory of historical causation under consideration here emphasizes the structuring role of intermediate factors (of which transport is a good example) and the importance of contingency—e.g. policy choices made at a specific point in time that structure future developments. Transportation systems appear to offer important examples of both points: that transportation represents a causal factor that influences social developments in very similar ways across many social and historical settings; and that there are crucial contingencies that influence the unfolding of a given transport system (Chicago rather than St. Louis, steam traction rather than electric motors, a rail network designed for military needs for mobilization rather than efficient economic activity throughout the country). Finally, transportation represents a factor, unlike climate, in which there is an internal process of development that can be studied using the methods of the history of technology, the history of business organization, and the tools of the new institutionalism. Transportation has its own internal history that can be analyzed and theorized with profit. And careful study will demonstrate that there are important structural and institutional differences in the way in which transportation technologies are implemented that themselves have important historical consequences across contexts, as demonstrated in Frank Dobbin’s treatment of the differences in the state and regulatory contexts in France, England, and the US in the early implementation of railways (Dobbin, 1994).

The idea to be considered is something like this: the system of transportation available at a given time creates a framework of opportunities and constraints that have deep causal consequences for historical development. It creates opportunities for individuals within the context of a specific but evolving set of economic arrangements and institutions. It creates the pathways through which people, goods, and ideas flow within and across societies—and these movements themselves have consequences. The system of transportation facilitates a certain kind and intensity of military power. It creates the feasibility of a certain kind and intensity of state-society relations (e.g. fiscal and police powers). It is possible to provide an abstract framework in terms of which to analyze transportation systems. And the implications that come along with this abstract framework may facilitate our understanding of phenomena that seem distant from transportation.

Transportation is a contingent historical product because its emergence and the particular features of its underlying assemblages of technologies and institutions themselves emerge though contingent processes. So the development of a particular system of transport is a contingent process of innovation and refinement, and the consequences of the establishment of the transport system are sometimes unexpected and radical.

Transportation has deep effects on social development, including the pattern and pace of the extension of settlement, the course of economic development (by enlarging regional and national markets and lowering costs of delivery), and facilitating the flow of ideas, bodies of knowledge, and innovations. Let us turn, then, to some of the factors and mechanisms through which transport influences history. We can attempt to categorize the effects of transport by exploring likely effects flowing from the transport of goods, people, and ideas.

The flow of goods that is effected by a transport system leads to market expansion (increasing availability of goods over a larger region), market integration (price correlations across space), greater commercialization (more production for the market as a result of broader and more predictable markets for goods), broader patterns of consumption, and diffusion of technology (as new potential users are exposed to new products, tools, and processes).

Easier movement of people creates equally important and equally visible effects. Long distance migration depends on transportation; symmetrically, an increase in transport efficiency and convenience will predictably increase the volume of migration. At the more local scale (inter-village, inter-city) improved transport increases the ability of people to seek employment, goods, and services at greater distance—thereby creating the possibility of ring settlements around higher-level places. Improved efficiency of the movement of people has important effects on the state and other dispersed organizations. If it takes the representative of the Emperor 14 days to travel from Beijing to Hankow, the ability of the Emperor to control events is clearly limited. When rail travel shortens this trip to 2 days, the administrative grasp of the state is enhanced. And if it takes a week to move reliable troops into position in defense against rebels, clearly the state’s ability to control rebellion is weak.

The movement of ideas that is facilitated by more effective transport is equally important. The movement of ideas depends on the movement of people and goods, but the effects are important and independent. The circuits of White Lotus teachers and martial arts instructors brought heterodox ideas to many parts of rural Shandong in the late Qing—with dramatic effects in the production of millenarian rebellion. The distribution of newspapers in the American West by rail allowed for a form of national unity that would otherwise have been impossible. The diffusion of new farm machinery and the cultivation techniques that accompanied depended profoundly on the network of railroads that crossed the west.

What are the obvious implications of new transport capabilities? First, patterns of settlement are plainly organized by available transportation facilities. Population grows around nodes and termini of transport systems. Second, transportation opportunities determine the extension and integration of markets for a variety of goods and services. If it costs 10 cash to produce a picul of rice but 100 cash to transport it 20 miles; then the grain market will not be very extensive. Third, there are obvious military consequences created by transportation networks. If armies are forced to march to their stations and carry their food, weapons, and water with them; the effective range of an army is limited. Slightly less obvious are the consequences for the diffusion of people and ideas that are created by a transport network. If New York newspapers are carried by the east–west train, then all the settlements along the way are potentially influenced by ideas, political trends, and styles represented in the pages of the newspaper. And if union organizers or anti-tax activists are extended in their reach by the existence of a new rail link between St. Louis and New Orleans—then we can expect a surge of political activity along these lines.

What are the non-obvious consequences? Can more efficient transport impede economic development? It can, in that it can readily extinguish local production when extra-local products begin to show up. It can spread crime, when criminals can make more efficient use of transport; the crime spree of Bonnie and Clyde would not have been possible without the automobile. (There is a letter in the Henry Ford Museum from Clyde Barrow to Mr. Henry Ford thanking him for the high-speed automobile the couple used.) More prosaically, the Interstate highway system facilitates the smuggling of drugs and untaxed tobacco from south to north, and it is possible to track the spread of sexually-transmitted diseases from truck stop to truck stop along major trucking routes.

Transport is also a limiting and/or facilitating condition of economic integration. The cost of transport per unit of a good plays a critical role in the regional scope of markets for the good. Some of the obvious factors: high mass, low price commodities—for example, grain—will have limited markets in circumstances of inefficient transport. Innovation of a low price mass transport option will abruptly increase the regional scope of markets for that good. Transport cost is less significant as a limiting factor for high-value, low bulk goods—tea, spice, and electronic components. Perishable commodities have a similar logic. Slow transport severely limits the scope of perishable commodity markets such as fruits and vegetables.

Are there unanticipated and perverse consequences that can emerge as a result of enhancement of service? Cities that are bypassed by new routes lose economic vitality—for example, Worcester, Massachusetts suffered economically when the Massachusetts Turnpike was routed so as to avoid passing near the city. Some traffic specialists maintained that the third harbor tunnel in Boston would increase congestion, by giving the public the impression that it will be more convenient to drive to the airport. Speeding up the velocity of travel on the tributary roads may lead to staggering traffic jams on the trunk road—with greater lost time overall. And it turns out that transportation systems display surprising system effects—for example, non-linear patterns of rail congestion.

Let us consider the question of causal influence. Transportation is particularly important in the view that I offer of social explanation under the framework of methodological localism. Individuals make choices, large and small, within the context of the space of opportunities and powers that are available to them. And transportation constitutes one particularly fundamental such source of opportunities and powers. Transportation is a factor that creates an institutional logic for the individuals, organizations, and structures within a society at a specific moment in time, imposing constraints and creating opportunities for them to achieve their goals. Traders exploit the opportunity to push further up a river when motorized boats become available, and people choose to settle in more remote places. Fishermen push further out into deep ocean when more seaworthy ships become available (Fagan, 2000). Smugglers take advantage of the wheel wells of aircraft. And so forth. Using the framework of methodological localism, we can understand the historical dynamics of a social setting that are created by the transport network along these lines:

Individuals have a set of purposes; movement of people and goods influences their ability to achieve these purposes; individuals will adapt opportunistically to the opportunities and constraints created by the transport system; and large social patterns (e.g. patterns of settlement, market integration) emerge as the consequence of the large number of independent actions and choices made by individuals in the population.

How does the transport system influence historical events? It does so as a causal mechanism embedded within the opportunities and constraints available to actors. It presents actors with a specific set of opportunities and constraints as they pursue their plans and purposes. To the extent that the new option permits the actor to better achieve his goal, his behavior and choices will change accordingly. This is especially true with regard to residence, employment, and business activity. But it also extends in the direction of technology change. We can expect some actors to look for ways of taking advantage of the new technology—of refining, perfecting, or extending it. So we can expect entrepreneurial activity to take place around the implementation of the system. Likewise, we can expect agents of the state to seize opportunities of interest in and around the transport system—e.g. as a powerful tool for military mobilization. The transport system is thus a locus for individual agency.

These effects all derive from the purposeful choices of individuals. Equally interesting are the unintended consequences of a particular direction of transport technology—the creation of isolated suburban communities, the transport of criminal activity, the social inertia behind the automobile, the values and lifestyle choices that emerge as a result of suburbia.

5.4 Many Small Causes

When large historical events occur, we often want to know the causes that brought them about. And we often look at the world as if these causes too ought to be large, identifiable historical factors or forces. Big outcomes ought to have big, simple causes.

But what if sometimes the historical reality is significantly different from this picture? What if the causes of some “world-historical events” are themselves small, granular, gradual, and cumulative? What if there is no satisfyingly simple and macro answer to the question, why did Rome fall? Or why did the American Civil War take the course it did? Or why did North Africa not develop a major Mediterranean economy and trading system? What if, instead, the best we can do in some of these cases is to identify a swarm of independent, small-scale processes and contingencies that eventually produced the outcome?

Take the fall of Rome. Rather than there being a single large cause for this catastrophe, it is possible that the collapse of the empire resulted from a myriad of very different contingencies and organizational features in different parts of the empire: say, logistical difficulties in supplying armies in the German winter, particularly stubborn local resistance in Palestine, administrative decay in Roman Britain, population pressure in Egypt, and a particularly inept series of commanders in Gaul. Too many moving pieces, too much entropy, and some bad luck in personnel decisions, and administrative and military collapse ensues. Alaric sits in Rome.

What an account like this decidedly lacks, is a story about a few key systemic or environmental factors that made collapse “inevitable”. Instead, the account is a dense survey of dozens or hundreds of small factors, separated in time and place, whose cumulative but contingent effect was the observed collapse of Rome. There is no simple necessity here—“Rome collapsed because of fatal flaw X or environmental pressure Y”—but instead a careful, granulated assessment of many small and solvable factors.

But here is a different possible historical account of the fall of Rome. An empire depends upon a few key organizational systems: a system of taxation, a system of effective far-flung military power, and a system of local administration in the various parts of the empire. We can take it as a given that the locals will resent imperial taxation, military presence, and governance. So there is a constant pressure against imperial institutions at each locus—fiscal, military, and administrative. In order to maintain its grip on imperial power, Rome needed to continually support and revitalize its core functions. If taxation capacity slips, the other functions erode as well; but slippage in military capacity in turn undermines the other two functions. (Tilly, 1990 and Mann, 1986 offer theories of large premodern states and empires along these lines.)

And now we have a possible basis for a satisfyingly simple and systemic explanation of the fall of Rome: there was a gradual erosion of administrative competence that led to increasingly devastating failures in the central functions of taxation, military control, and local administration. Eventually this permitted catastrophic military failure in response to a fairly routine challenge. Administrative decline caused the fall of Rome.

Neither of these stories—the “many small causes” story or the “systemic administrative failure” story—may in fact be historically credible. But either could be historically accurate. And this is enough to establish the central point: we should not presuppose what the eventual historical explanation will look like. There is no reason to expect a priori that large events will conform to either model. It may be that some great events do in fact result from a small number of large causes, while others do not. So the point here is one about the need to expand our historical imaginations, and not to permit our quest for simplicity and generality to obscure the possibility of complexity, granularity, and specificity when it comes to historical causation.

5.4.1 Causes of the Chinese Revolution

Let us consider a question fundamental to twentieth-century world history: why did the Chinese Communist Revolution succeed? Was it the result of a few large social forces and structures? Or was this a case of many small causes operating at a local level, aggregating to a world-historical outcome?

It should first be noted that the CCP’s path to power was rural rather than urban. The Guomindong (GMD) had effectively expelled the CCP from the cities in 1927 and had detached the Communist Party from urban workers. (Note that this runs directly contrary to the expectations of classical Marxism, according to which the urban proletariat is expected to be the vanguard of the revolution. A massive contingency intervened—Chiang Kai-shek’s ability to wipe out the urban Communist movement in the Shanghai Massacre in 1927.) Further, the turning point in the fortunes of the CCP clearly occurred in the “base areas” during the Sino-Japanese War (1937–1945): the areas of rural China where the CCP was able to establish itself as the dominant political and military force opposed to the Guomindong and the Japanese Army. The success of the revolution, therefore, depended on successful mobilization of the peasantry in the 1930s and 1940s. How are we to account for its success?

This question has naturally loomed large in Western discussions of the Chinese Revolution since 1949. Two influential theories offer political culture and class conflict as causes of revolution, and neither of these high-level theories appears to be altogether satisfactory. A more plausible analysis refers to the local politics of class. Rather than postulating a single large causal factor, it is more plausible to understand CCP success as a concatenation of a number of small causes and advantages, deployed with skill and luck to a successful national victory.

Consider first a theory based on political culture. Chalmers Johnson argued in Peasant Nationalism and Communist Power (Johnson, 1962) that the CCP succeeded in mobilizing peasant support during the Sino-Japanese War because (a) peasants were nationalistic and patriotic, and determined to expel the Japanese, and (b) the CCP was the organization that showed the greatest military and organizational ability to oppose the Japanese military presence in China. Johnson maintained that the CCP downplayed its social program (class conflict, land reform, etc.) during the Anti-Japanese War, in the interest of a united front against the Japanese, and that its social goals played little or no role in its mobilizational successes. Peasants therefore supported the CCP out of nationalism, and were, perhaps, unpleasantly surprised at the social program that emerged after the defeat of the Japanese. This theory made a feature of political culture—nationalist identity—the central determinant of largescale collective action.

Mark Selden, an American sociologist, advanced a very different view of the CCP’s success in The Yenan Way in Revolutionary China (Selden, 1971). He offered a class-conflict model, according to which Chinese rural society possessed an objectively exploitative class structure in opposition to which the CCP successfully mobilized support. Landlords, moneylenders, and the state exploited the peasantry by extracting rent, interest, and taxes. The CCP provided a program of social revolution aimed at overthrowing this exploitative order, and peasants followed this program, and supported the CCP, in order to pursue their class interests.

Johnson’s theory has not stood the test of time very well, in part because there is a dearth of evidence to support the idea that ordinary Chinese people did in fact possess the nationalistic identity and political commitments that the theory postulates. Serious weaknesses in Selden’s argument are substantial as well, however. Selden assumed that the realities of exploitation and class are relatively transparent, so that peasants more or less immediately perceive their class interests. And he assumed that collective action follows more or less directly from a perception of class interests: if there is a plausible strategy for furthering class interests through rebellion (i.e., the CCP), then peasants will be disposed to do so. However, the social reality of China was much more complex than this story would allow, with region, lineage, and village society existing as a more immediate social reality for most rural people than class and exploitation. So neither Johnson nor Selden provide a framework within which a fully satisfactory theory of the revolution can be constructed. (Lucien Bianco discusses many of these rural complexities in Peasants without the Party; Bianco, 2001.)

A more convincing view has been offered by a third generation of historians of the Chinese Revolution. One of those historians is Yung-fa Chen in Making Revolution: The Communist Movement in Eastern and Central China, 1937–1945 (Chen, 1986). Chen offers an explanation of the CCP’s mobilization successes that depends upon a micro-level analysis of the local politics created in Eastern China as a result of local social arrangements and the Japanese occupation. Methodologically his approach is microfoundational and localistic rather than sweeping and mono-causal. And Chen’s main findings disagree in some important ways with both Johnson and Selden.

The main elements of Chen’s analysis are these. First, he confirmed the Marxist view that the CCP had a coherent social program (land reform and fundamental alteration of rural property arrangements), and that the CCP made this program a central part of its mobilization efforts. This program implicitly defined a form of class analysis of rural Chinese society into poor peasants, middle peasants, rich peasants, and landlords, and endeavored to sharpen conflicts among these. Second, though, Chen rejected the view that these rural class relations and oppositions were fully transparent to participants, needing only the appearance in the village of a few ideologically correct cadres to mobilize peasant support. Rather, Chen held that the wide variety of rural social relations—lineage, family, religious organization, patron-client, friendship—worked as powerful brakes on the emergence of class consciousness. So a determined program of class-consciousness raising was needed, which the CCP attempted to provide through its “speaking-bitterness” sessions.

And, Chen maintained, peasants were highly skeptical of the ability of outside organizations to protect them against the wrath of local powers (landlords, officials) once the military threat had disappeared. A central problem of mobilization, then, was to create a local organization and militia that was capable of fending off Japanese and GMD military attack; that was sufficiently stable as to lend confidence that peasants could rely on it in the future; and to put forward a social program that would leave it well-positioned to begin the process of socialist reform through land reform, reform of credit institutions, and ultimately collectivization of agriculture and industry.

The heart of Chen’s analysis depends on the assumption that peasants are rational political actors, and will support a political organization only if they judge that (a) it will support their local interests and (b) it will be powerful enough to support its local followers. (This has a lot in common with Samuel Popkin’s arguments in The Rational Peasant; Popkin, 1979.) Chen then considers available data on a large number of local communities in Eastern China during the war years in the base areas of the revolution, and finds that the CCP did a skillful job of satisfying both requirements. It was effective in creating military and political organizations capable of protecting local interests; and it was effective in communicating its class analysis to peasants in sufficient degree to lead to support for its revolutionary social program. But, contrary to the nationalist thesis offered by Chalmers Johnson, he argues that the CCP was very skillful in avoiding direct military confrontation with the Japanese Army.

Another impressive effort to provide a new reading of aspects of the Chinese Revolution is provided by Odoric Wou in Mobilizing the Masses: Building Revolution in Henan (Wou, 1994). Focused on Henan Province, Wou attempts to uncover the complex set of factors that permitted the Communist Party to mobilize mass support for its program. He emphasizes organizational and political factors in his account: the strategies and organizational resources through which the CCP was able to move ordinary workers and peasants from concern with local interests to adherence to a national program. Wou provides fascinating detail concerning Communist efforts to mobilize miners and workers, Red Spears and bandits, and peasants in Henan Province.

Wou makes plain the daunting challenges confronting Communist cadres in their efforts to mobilize support at the village level: mistrust of outsiders, the entrenched political power of elites, and the localism of peasant interests in the region. Wou describes a social-political environment in the countryside that is reminiscent of Philip Kuhn’s account of the situation of local militarization during the Taiping Rebellion in eastern China—one in which elite-dominated militias had evolved as an institution of self-defense against bandits and sectarian organizations (Kuhn, 1970a).

One of the most interesting and surprising findings that Wou puts forward is his contention that mobilization in Henan was not centered in remote and backward border areas, but rather included both remote and commercialized peasant villages (Wou, 1994, p. 129). This is somewhat inconsistent with Chen’s analysis, who focuses precisely on the tactical advantages of remoteness offered by the base areas.

Wou also makes an effort to crack the riddle of peasant mentality in China. Are peasants inherently conservative? Are they latently revolutionary, awaiting only the clarion call of revolution? Both, and neither, appears to be Wou’s assessment (Wou, 1994, p. 161). Wou finds a popular equalitarianism within Chinese peasant culture that provides a basis for Communist mobilization around an ideology of redistribution (p. 151); but equally he finds an entrenched hierarchicalism within Chinese popular culture that made subversion of elite power more difficult for Communist cadres (Wou, 1994, p. 135).

Wou also considers the political environment created for the CCP by the Sino-Japanese War. (This is the period treated by Chen.) Guomindang power virtually collapsed in Henan Province, and the Japanese occupied eastern Henan in 1938. The three-way struggle between the Japanese, the Guomindang, and the Communist Party gave the Party new opportunities for mobilization against both its enemies. Here Wou makes the important point that structural circumstance—military fragmentation of society, in this case—only provides the opening to successful mobilization, not its sufficient condition. The organizational and strategic competence of the CCP was needed in order to make effective use of these new opportunities for mobilization. Successful play of the game of coalition politics gave the CCP important advantages during this period, and created a position of strength that contributed substantially to post-war success of the movement.

A central tenet of Wou’s analysis is the importance of Communist efforts to improve material conditions of life for the populations it aimed to mobilize. Famine relief, formation of production cooperatives, and revival of the silk industry represented efforts by the Party to demonstrate its ability to provide tangible benefits for local communities (Wou, 1994, pp. 314–326). These efforts had at least two beneficial effects: they provided material incentives to prospective followers, and, less tangibly, they enhanced confidence among villagers in the competence and endurance of the Party.

Both Chen and Wou make important contributions within a third generation of historical scholarship and interpretation of the Chinese Revolution. Their accounts are to some extent complementary and to some extent inconsistent—as one would expect in detailed efforts to answer profound questions about causation. And both accounts share an important historical insight: it is crucial to push down into the local village circumstances of social life and mobilization that the CCP faced as it attempted to generate commitment and support for its movement if we are to understand why it succeeded in mobilizing support from millions of rural people.

5.5 General and Specific Causal Hypotheses

It is worthwhile noticing that we can ask causal questions at two extremes of specificity and generality. We can ask why the Nicaraguan Revolution occurred—that is, what was the chain of circumstances that led to the successful seizure of power by the Sandinistas? This is to invite a specific historical narrative, supported by claims about causal powers of various circumstances. And we can ask why twentieth-century revolutionary movements succeeded in some circumstances and failed in others—that is, we can ask for an account of the common causal factors that influenced the course of revolution in the twentieth century. In the first instance we are looking to put forward a causal hypothesis about a particular event; in the latter we are seeking a causal explanation concerning the behavior of a class of events.

Take the idea that the outbreak of hostilities in World War I was caused by the assassination of Franz Ferdinand of Austria in 1914. This claim might be supported by identifying a chain of events that proceeded from the assassination, to decisions in various capitals, to the mobilization of troops, to the outbreak of fighting. The assassination was the spark that led to the conflagration. But this is a purely singular chain of events, and there is no regular connection between occurrences of this set of events and the outbreak of war. The sequence of causal links in this story involves pure contingency at many stages. Assassinations don’t generally cause wars; sometimes they do and sometimes they don’t. Events in the category of “political assassination” do in fact have a set of causal powers—through the influence that a political assassination can have on powerful decision-makers and public opinion. But there is no single mechanism that links assassinations to the outbreak of war.

Much inquiry in the social sciences has to do with singular causal processes (historical outcomes): individual revolutions, specific experiences of modernization and development, specific histories of collective action. Charles Tilly’s career-long treatment of the collective political behavior of the French is a case in point; Tilly attempts to identify a characteristic tradition of French political action, and attempts to identify the historical occurrences which gave this tradition its specificity (Tilly, 1986). But Tilly is also interested in identifying common social mechanisms of contention; and this allows him to identify general causes as well as singular causes.

Historical investigation and “process tracing” permit us to analyze particular singular causal sequences—for example, “a floating iceberg caused the sinking of the Titanic.” This kind of singular historical analysis permits discovery of the causal mechanisms and contingent happenings that were involved in the production of the event to be explained.

A general hypothesis about causation is based on a discovery of a pattern across a number of similar cases. For example, Theda Skocpol’s States and Social Revolutions (1979) attempts to discover causal regularities leading to the occurrence of revolution that emerge from study of a small number of particular revolutions, and Jeffrey Paige’s Agrarian Revolution (Paige, 1975) offers a large-N study of cases of revolution and rebellion to attempt to discover common causal conditions. And through either type of study we might arrive at evidence supporting general causal claims like these: “the occurrence of subsistence crises is a causal factor in the occurrence of rebellion,” “a strong state inhibits the occurrence of rebellion,” and “international crises make rebellions more likely.”

To assert that A’s are causes of B’s is to assert that there is a typical causal mechanism through which events of type A lead to events of type B. Here, however, we must note that there are rarely single sufficient conditions for social outcomes; instead, causes work in the context of causal fields. So to say that revolutions are causally influenced by food crisis, weak states, and local organization, is to say that there are real causal linkages from these conditions to the occurrence of revolution in specific instances. If we have enough cases, then these causal mechanisms will also produce some regularities of association between the hypothesized causal factors and the outcome; but without a large number of cases these regularities will be difficult or impossible to discern.

To what extent is such a causal analysis of a unique event explanatory, rather than merely true? The account is explanatory if it identifies influences that commonly exert causal power in a variety of contexts, not merely the case of the French in 1848 or Russia in 1917. And a case study that invokes or suggests no implications for other cases, falls short of being explanatory.

I will put it forward as a methodological maxim that a causal assertion is explanatory only if it identifies a causal process that recurs across a family of cases. A historical narrative is an answer to the first sort of question (“why did this particular event come about?”); such a narrative may or may not have implications for more general causal questions. A true causal story is not always explanatory.

There is another issue raised by this topic of general and particular causal hypotheses, which has to do with the idea of “over-determination.” Return to the case of World War I. It might be argued that there were broad structural forces at work that were steadily increasing the likelihood of war throughout 1912–1914—deepening economic and geographical conflicts of interest among the great powers, large-scale military planning by various governments, and a worsening arms race, for example; so war was “inevitable” with or without the spark created by the assassination of the Archduke. If this event had not occurred, some other instigating event would have cropped up; so the conflagration was inevitable. On this interpretation, the assassination of the Archduke was a critical part of the actual pathway leading to the outbreak of war; but there were many other hypothetical pathways that would have led to the same result. So it is the background structural conditions that were the real and substantive causes of World War I—not the contingent and accidental fact of the assassination in 1914.

5.6 Causal Reasoning in Meso-History

Here, then, we can come to a set of conclusions. Social entities exercise causal powers through their capacity to affect the choices and behavior of the individuals who make up these entities, and through no other mechanism. Once the ground is cleared along the lines delineated by the notion of meso-history—emphasizing both the importance for the historian of the particular contingencies of a specific historical context and the causal efficacy of the broad structures and processes that are in play—the challenge for the historian of large processes is more apparent. It is to seek out the specific institutions, structures, and processes that are embodied in a given historical setting; to identify the possibilities and constraints that these structures create for agents within those settings; and to construct explanations of outcomes that link the causal properties of those structures to the processes of development that are found in the historical record. Finally, it is useful for the historian of large processes to explore the space of “what might have been”—the space of contingent alternative developments that were equally consistent with the configuration of large structures and particular circumstances at a given time.

We can come to several concluding observations about causal explanations in history.

  • Social entities exercise causal powers through their capacity to affect the choices and behavior of the individuals who make up these entities, and through no other avenue.

  • Social processes should be expected to demonstrate a significant level of contingency, path-dependency, and variability, given the multiple types of causal mechanisms, institutional variations, and features of individual agency that come together to bring about a given outcome.

  • We should not expect to discover strong “social laws” or governing social generalizations across social phenomena and settings. Instead, the most we should expect are the exception-laden regularities that derive from “common structures of agency” in multiple social settings.

  • It is possible to offer valid and justified causal explanations of singular events, by discovering through historical and empirical research the traces of the causal mechanisms that brought about these events.

  • A central intellectual role for empirical theories in the social sciences and social psychology—“theories of the middle range”—is the formulation of descriptions of typical causal mechanisms in social circumstances of “socially situated agents”.

It is difficult to discern a valuable intellectual role for sweeping social theories intended to apply to all social settings—general theories of social organization and change. Instead, we should recognize the contingency and variability of the social world, and look rather to contextually defined social relations and the causal mechanisms that derive from them.