A catalogue of social mechanisms

In an earlier post I made an effort at providing the beginnings of an inventory of social mechanisms from several areas of social research. Here I’d like to go a little further with that idea in order to see how it plays into good thinking about social-science methodology.

Some Types of Social Mechanisms CONTENTION Escalation Brokerage Diffusion Coordinated action Social appropriation Boundary activation Certification Framing Competition for power COLLECTIVE ACTION Prisoners' dilemma Free rider behavior Convention Norms Selective benefits Selective coercion Conditional altruism Reciprocity ORGANIZATIONAL ENFORCEMENT Audit and accounting Supervision Employee training Morale building Leadership NORMS AND VALUES Altruistic enforcement Person-to-person transmission Imitation Subliminal transmission Erosion Charisma Stereotype threat

ECONOMIC ACTIVITY Market Auction Ministry direction Contract Market for lemons Democratic decision making Producers' control Soft budget constraint GOVERNMENT Agenda setting Cyclical voting Log rolling Regulatory organizations Influence peddling STATE REPRESSION Secret police files Informers Spectacular use of force Propaganda Deception Control of communications systems SOCIAL COMMUNICATIONS Interpersonal network Broadcast Rumor Transport networks SYSTEM EFFECTS Flash trading Interlocking mobilization Overlapping systems of authority (Brenner) Non-linear networks

These mechanisms have been collected from a wide range of social scientists and researchers -- Charles Tilly, Robert Axelrod, Elinor Ostrom, George Akerlof, Robert Bates, Mancur Olson, Mayer Zald, John Ferejohn, Janos Kornai, Claude Steele, and Charles Perrow, to name a few.

There are at least two kinds of questions we need to ask about a collection like this.

First, where do the entries come from? What kinds of scientific inquiry are required in order to establish that things like these are indeed mechanisms found in the social world?

The most general answer to this question concerning discovery is that much research in the various disciplines of the social sciences is specifically directed at working out the contours of mechanisms like these. Political scientists who focus on legislatures and the US Congress have become expert on identifying and validating the institutional and voting mechanisms through which legislative outcomes come to effect. Organizational sociologists study the inner workings of a range of organizations and are able to identify and validate a wide range of mechanisms at work within these organizations. Economic anthropologists and theorists study the ways in which economic transactions are conducted in a range of human settings. Social psychologists identify many of the ways that individuals acquire normative beliefs and transmit them to other individuals. The greatest difficulty in constructing a table like this is not at the level of identifying mechanisms that might be included; it is the problem of limiting the number of mechanisms identified to a more or less manageable number. There is some reason to fear that social scientists have identified thousands of mechanisms in their research, not dozens.

And second, what role does a table like this play in the conduct of research in the social sciences?

In In Search of Mechanisms: Discoveries across the Life Sciences Craver and Darden argue that biologists often approach novel phenomena with something like this table in the backs of their heads -- an inventory of known causal mechanisms in the domain of biology. From there they attempt to solve the puzzle: what combination of known mechanisms might be concatenated in order to reproduce the observed phenomenon?

Strikingly enough, this description of a heuristic for arriving at an explanatory analysis of a situation has a lot in common with the way that McAdam, Tarrow, and Tilly proceed in Dynamics of Contention. (Here is a more developed analysis of their mechanisms-based approach; link.) MT&T argue that there is a relatively manageable list of social mechanisms that can be observed in many cases of social contention. And they approach new instances with the idea that we may be able to understand the dynamics of the case by teasing out the workings of some of those mechanisms. It seems that MT&T are involved in both parts of the inquiry -- discovery and isolation of recurring mechanisms of contention, and application of these discoveries to the explanation of specific episodes of contention.

For example, they introduce their case studies in Part III of the book in these terms:

Part III of the study takes up three distinct literatures regarding contention -- revolution, nationalism, and democratization -- in view of the paths our quest has followed. The goal of that concluding section is to emphasize the commonalities as well as the differences in those forms of contention through an examination of the explanatory mechanisms and political processes we have uncovered in Parts I and II. (kl 511)

And a few paragraphs later:

Let us insist: 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. (kl 519)

Here is how they summarize their attempt to explain particular episodes of social contention. They focus on a "number of loosely connected mechanisms and processes":

• A mobilization process triggered by environmental changes and that consists of a combination of attribution of opportunities and threats, social appropriation, construction of frames, situations, identities, and innovative collective action.
• A family of mechanisms still to be elucidated around the processes of actor and identity constitution and the actions that constitute them.
• A set of mechanisms often found in trajectories of contention that recurs in protracted episodes of contention, competition, diffusion, repression, and radicalization. (kl 941)

And this body of social mechanisms is taken to provide a basis for historically grounded explanations of the forms of contention observed in specific cases.

This seems to parallel fairly closely the intellectual process that Craver and Darden describe in the case of biology: create an inventory of common causal mechanisms and analyze new cases by trying to see to what extent some of those known mechanisms can be discerned in the new material.

This account of an important type of social science research resonates well with a broad range of social science disciplines. It aligns with Robert Merton's notion of "theories of the middle range" in the social sciences, and the idea of developing a toolbox of patterns of social behavior on the basis of which to explain specific episodes. Rather than looking for general theories on the basis of which to unify wide swaths of the social world under a deductive explanatory system, this mechanisms-based approach suggests coming at social explanation piecemeal: finding the components and sub-processes of observed social ensembles, on the basis of which we can explain some aspects of the behavior of those ensembles.

We might usefully consider two additional questions. First, is there a theoretically useful way of classifying social mechanisms (formation of the individual actor, collective action, communication, repression, collective decision making, ...)? Can our catalogue provide content-relevant "chapters"? We might argue that a good taxonomy of social mechanisms actually provides a way of theorizing the main dimensions of social activity and organization. And second, are there more fundamental things we can say about how some or many of these mechanisms work? Does a good theory of the actor and a good theory of social organizations suffice to account for the workings of a great many of these mechanisms? If we respond affirmatively to this question, then once again we may have made a small degree of progress towards offering a somewhat more general theory of the social world.

Craver on mechanisms methodology

Carl Craver and Lindley Darden provide in In Search of Mechanisms: Discoveries across the Life Sciences an extensive treatment of what a mechanisms-based methodology looks like. Their work originates in study of the biological sciences, but I find that much of what they have to say is very helpful in the philosophy of social science as well.

Craver and Darden argue that the biological sciences have largely adopted a mechanisms-centered view of the nature of their science. So what is a mechanism, on their view?

Mechanisms are how things work, and in learning how things work we learn ways to do work with them. Biologists try to discover mechanisms because mechanisms are important for prediction, explanation, and control.... Mechanisms are entities and activities organized such that they are productive of regular changes from start or set-up to finish or termination conditions. (kl 581)

Fundamentally Craver and Darden  argue that a search for mechanisms is frequently a guided and constrained process, involving an attempt to match the observed activities of the system with a concatenation of known mechanism components. They want to provide a more granular account of the process of research and discovery in science, and they take issue with the idea of a flash of inspiration as the source of scientific insight. Instead, they see the process of a great deal of scientific research as one in which a methodical effort at puzzle-solving takes place, trying out different combinations of known mechanisms to see whether they may serve to explain the phenomenon in question.

In short, one often begins the search for mechanisms with a ready-made layout of the space of possible mechanisms, and the goal is to use empirical findings to eliminate regions of that space. The nature of the phenomenon and the store of accepted mechanism types thus work together to frame the discovery problem: to reveal the layout of the space of possible mechanisms and perhaps to tell one how to decide among them. (kl 1595)

They don't mean to say that there is no place for novelty or originality in scientific research; but they argue for a kind of cumulative process for much of the scientific work of discovery that builds upon the prior discovery of mechanisms and components of mechanisms.

Although occasionally biology calls upon a Darwin or a Harvey to introduce an altogether novel kind of mechanism, most episodes of mechanism discovery play out within the space of known mechanism types within a scientific field. (kl 1604)

There are many interesting and useful contributions offered in the book. One is represented in the following figure (5.1), in which Craver and Darden point out that there are multiple ways in which mechanisms are invoked in scientific research, not just one. The most common way in which we think of mechanisms is as "producers" of outcomes -- the first panel of the figure. But there are several other valid uses as well. There is the "X underlies Y" relation (panel 2), in which we provide a set of mechanisms X as an explanation of how the properties of Y are constituted; and there is the "X maintains Y" relation, in which we provide a set of mechanisms X as an explanation of the homeostasis of Y (the feedback loops and corrective mechanisms that return Y's properties to equilibrium after a period of drift or change).

 

 

Another interesting observation that C-D develop is the idea of "modular subassembly". 

This process, modular subassembly, involves reasoning about how mechanism components might be combined in surprising ways. One hypothesizes that a mechanism consists of (either known or unknown) modules or types of modules. One cobbles together different modules to construct a hypothesized how-possibly mechanism, guided by the goal of finding modules to fill all the gaps in a productively continuous mechanism. In doing so, scientists draw upon their knowledge of the store of types of entities and activities and modules (i.e., interconnected entities and activities that have a particular function). (kl 1726)

This description invokes the idea of realistic inquiry into the subprocesses that give continuous action to the mechanism. Essentially this invokes the idea of opening the black box of the mechanism and asking how the mechanism itself works. And the ontological assumption is that the mechanism consists of discrete sup-processes.

 

A third valuable idea that is advanced in this work is the idea of multi-level mechanisms. 

Biological mechanisms typically span multiple levels. Scientists working at higher levels work on ecosystems, populations, and the behaviors of organisms within their environments. Others study mechanisms within organisms, such as the nervous or circulatory systems, and mechanisms within organs and cells, and, ultimately, mechanisms with smaller entities, such as macromolecules, small molecules, and ions. Different fields of biology are often (to a first approximation) associated with different levels. (kl 688)

This is an important point for social scientists as well, given the common tendency to bifurcate into "macro" and "micro" features of the social world. Instead, C-D give further grounds for insisting that there is a wide and continuous range of levels of aggregation in the social world, and that it is perfectly legitimate to formulate representations of mechanisms that span these levels. 

 

A key feature of C-D's view of biological research is the notion that researchers make use of a wide but known stock of existing mechanisms in their efforts to understand novel phenomena. What are some of those mechanisms? Here is a very interesting table of miscellaneous biological mechanisms that Craven and Darden provide:

 

 

This table is useful exactly because it is not intended to be comprehensive or exhaustive. Rather, it is intended to provide a list of concrete mechanisms that have been observed and investigated in the biological sciences. And, as Craver and Darden argue, a large available base of known mechanisms provides a starting point for researchers who are confronting a novel phenomenon.

A collection of social mechanisms along these lines would also be valuable for researchers in the social sciences. Here is my own beginning of a table of social mechanisms:

Some Types of Social Mechanisms CONTENTION Escalation Brokerage Paramilitary organizations COLLECTIVE ACTION Prisoners' dilemma Free rider behavior Convention Norms Selective benefits Selective coercion ORGANIZATIONAL ENFORCEMENT Audit and accounting Supervision Employee training Morale building Leadership SOCIAL COMMUNICATIONS Interpersonal network Broadcast Rumor Transport networks

ECONOMIC ACTIVITY Market Auction Ministry direction Contract Democratic decision making Producers' control GOVERNMENT agenda setting Log rolling Regulatory organizations STATE REPRESSION Secret police Informers Spectacular use of force Propaganda Deception SYSTEM Flash trading Interlocking mobilization Overlapping systems of authority (Brenner)

How applicable is the Craver-Darden view of mechanism thinking when we turn to various areas of social research? There are obvious differences between the domains of biology and the social sciences, and this seems to be true when it comes to mechanisms.

One visible difference is the relative precision with which we can describe the workings of mechanisms in the two domains. The mechanism of "mismatch repair" mentioned in the C-D table under DNA Repair Mechanisms can be described in a great deal of precision, and this mechanism generally works in the same way in all settings. Compare that with the mechanism of "Audit and accounting" under Organizational Enforcement in my table above. This is also a "repair" function. But the audit function in an organization can be implemented in many different ways with varying degrees of coercion and voluntary compliance. So there is a much wider range of activities encompassed by "audit and accounting" than by "mismatch repair".

There is another kind of precision mismatch that seems to exist between biology and social science as well -- the idea that a mechanism produces the same results in a wide range of settings. Because of the molecular biology that underlies most of the mechanisms that C-D consider, these mechanisms perform like clock-work. Each tick leads to the same advancement of the wheel. But in the social world, the precision of relationship between input to a mechanism and output from the mechanism is much more slack. When a group of workers are called upon to support a wildcat strike, we may hypothesize that the free-rider mechanism will be invoked in this social setting. But free-riding may be so extensive as to cripple the strike, and it may be so limited as to barely influence the outcome at all. We can learn more about the social factors that differentiate these two outcomes. But the key point is that the mechanism is in play in both scenarios, but with very different effects.

One special strength of In Search of Mechanisms is the fact that it is a work of philosophy of science that is highly detailed in its treatment of some of the scientific content of a specific field. We cannot resolve the question of whether mechanisms are a good way of organizing scientific inquiry on the basis of apriori reasoning alone. Rather, we need to see how mechanisms-based reasoning is expressed in a range of scientific areas of inquiry. And this is exactly what Craver and Darden do in this book for a range of biological disciplines.

Are there meso-level social mechanisms?

It is fairly well accepted that there are social mechanisms underlying various patterns of the social world — free-rider problems, communications networks, etc. But the examples that come readily to mind are generally specified at the level of individuals. The new institutionalists, for example, describe numerous social mechanisms that explain social outcomes; but these mechanisms typically have to do with the actions that purposive individuals take within a given set of rules and incentives.

The question here is whether we can also make sense of the notion of a mechanism that takes place at the social level. Are there meso-level social mechanisms? (As always, it is acknowledged that social stuff depends on the actions of the actors.)

This question is analogous to two other similar issues in other special sciences:

• Are there information-system level causal mechanisms in human cognition?
• Are there cellular-level causal mechanisms in biological systems?

Or, to the contrary, are all mechanisms in sociology, cognition science, and biology properly understood to be carried out at the level of individuals, neurons, and biochemistry?

Here is my version of a definition of a causal mechanism (link):

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

And here is the definition offered by Doug McAdam, Sidney Tarrow, and Chuck Tilly in Dynamics of Contention:

Mechanisms are a delimited class of events that alter relations among specified sets of elements in identical or closely similar ways over a variety of situations. (kl 354)

We should begin by asking what it is that we are looking for. What would a meso-level mechanism look like?

Here is a start: it would be a linkage between two conditions or entities, each of which is itself a meso-level structure or entity. So a meso-level causal mechanism is one in which both C and O are meso-level entities or conditions and where C leads to O "always or normally".

Earlier I argued that meso-level entities possess causal powers: regular dispositions to produce specified effects, grounded in the substrate of social activity (link). If some of those effects O_i are themselves meso-level outcomes or structures, then our question here is answered. Any pair {C,O_i} is itself a meso-level causal mechanism. If, on the other hand, the causal powers of meso-level entities are restricted to changes in the behavior of individuals, then meso-level mechanisms do not exist.

McAdam, Tarrow, and Tilly address a very similar question in Dynamics of Contention, and they argue for what they call "relational mechanisms":

Relational mechanisms alter connections among people, groups, and interpersonal networks. Brokerage, a mechanism that recurs throughout Parts II and III of the book, we define as the linking of two or more previously unconnected social sites by a unit that mediates their relations with one another and/or with yet other sites. Most analysts see brokerage as a mechanism relating groups and individuals to one another in stable sites, but it can also become a relational mechanism for mobilization during periods of contentious politics, as new groups are thrown together by increased interaction and uncertainty, thus discovering their common interests. (kl 376)

Having formulated the question in these terms, it seems that we can provide a credible affirmative answer: it is possible to identify a raft of social explanations in sociology that represent causal assertions of social mechanisms linking one meso-level condition to another. Here are a few examples:

• Al Young: decreasing social isolation causes rising inter-group hostility (link)
• Michael Mann: the presence of paramilitary organizations makes fascist mobilization more likely (link)
• Robert Sampson: features of neighborhoods influence crime rates (link)
• Chuck Tilly: the availability of trust networks makes political mobilization more likely (link)
• Robert Brenner: the divided sovereignty system of French feudalism impeded agricultural modernization (link)
• Charles Perrow: legislative control of regulatory agencies causes poor enforcement performance (link)

We might also consider the possibility of compound meso-level mechanisms, in which M₁ produces M₂ which in turn produces M₃. Does the sequence also qualify as a mechanism? That depends on the strength of the relationships that exist at each link; if the conditional probabilities of the links fall low enough, then the compound probability of the chain is no longer sufficient to satisfy condition (ii) above ("initial condition normally leads to the outcome").

Essentially this question comes down to the tightness of the linkages that exist among the sub-components of social systems. If there are sub-components within bureaucracies that maintain their properties and are tightly linked to specified outcomes, then these can play a role within meso-level causal mechanism narratives. If, on the other hand, the effects of a given subcomponent of a social system vary widely over time and space, then that type of component does not play a useful role in a causal mechanisms analysis. So the question of how extensive meso-level causal mechanisms are is itself an empirical one; it depends on the specific features of the social world.

So it seems as though we can offer two related conclusions about the causal reality of meso-level entities: meso-level structures possess causal powers, and there are causal mechanisms that invoke meso-level entities as both input and output.

Causal narratives, mechanisms, and powers

A million termites move around industriously without supervisors or external coordination.  Some months later, a great structure has arisen — a termite cathedral mound. It is a structure that has apparent functionality (figure 2), it is oriented to the sun in a way that optimizes its ability to handle heat and cold, and the design plainly exceeds the cognitive or practical capacity of any single termite. How do they do it? (The BBC video below describes these mounds and their construction.)

This is a hard question because we know quite a bit about what the termites do not do. They do not have architects and project managers; they do not have blueprints guiding their work; they do not have a master plan. Instead, millions of independent organisms somehow coordinate their actions in ways that collectively result in the large structure.

 figure 1. The mound

figure 2. The structure of the mound

We would like to have an explanation for how this works; how the individual insects within this population behave in the ways that are necessary to create this vast complex structure.

One way of putting our explanatory needs here is to say that we are asking for a mechanism: what is the mechanism or ensemble of mechanisms that produce the collective behavior leading to the construction of the mound? What is it about the behavioral code of the insect that permits this collective behavior? This way of putting the problem is to highlight the mechanisms approach.

But we might better say, we are asking for an explanatory narrative, including elements like these:

• The insects have such-and-so behavioral routines (algorithms) embedded in their nervous systems.
• Behaviors are triggered by environmental circumstances and the activities of other insects around them.
• The triggered behavior in each insect contributes to a pattern of activity that leads to progressive “building” of the mound.

The force of the explanation hinges on the details we can learn about these powers and capacities of the termites as a species -- these behavioral algorithms. We want to know something crucial about the powers and capacities of the individual insects; we want to know how their routines are responsive to environment and other insects; and we want to know how the emerging structure of the mound leads to the modified activities of the insects over the process of construction.

This narrative highlights a topic we have considered several times before -- the idea of the causal powers of an entity. Most basically, we might look at the individual worker termite as robot controlled by a complex algorithm -- "when external circumstances X,Y,Z arise, carry out the Z routine." The causal powers of the individual worker termite are determined by its algorithm and its physical capacities -- salivation, moving around, carrying bits of mud, and so forth. And the task of explanation is to discover the nature of the algorithms and the ways in which the resulting behaviors aggregate to the observed physical structure of the mound.

We might observe, for example, that a certain kind of insect navigates a maze by following a simple rule: always keep the wall on your left. This rule will sometimes work well; sometimes it will not. But this observation suggests that the insect's central nervous system encodes the decision-making rule in this way. And we might also infer that "maze navigation" is important for the survival of the insect in its normal environment, and so its navigational algorithms will have been refined through natural selection.

We would also like to know something else about the insects and their powers: how did they come to have these particular capacities and algorithms? Here we have a well established explanation, in the form of the theory of the gene, natural selection, and the evolution of species characteristics through differential reproductive success. Here the explanatory challenge is to piece together the nature of the algorithms that would suffice to account for the observed collective outcomes.

It is also of interest in this example that there is a large field of research and discovery within complexity research that hinges on discovering the complex collective patterns that can emerge from simple routines at the level of the individual agent. For example, the "Game of Life" illustrates the power of cellular automata in generating complexity out of simple agent-level routines.

This example is a useful one, not primarily for entymologists, but for us as philosophers of social science. What would an explanation of this phenomenon look like? And a little bit of reflection seems to take us in the direction of some familiar ideas: the idea of things having causal powers that govern what they can do, the idea of the aggregation of complex outcomes from independent activities of large numbers of agents (agent-based models), and the idea that a good explanation gives us an empirically supportable understanding of how something works.

"How does it work" questions

Source: Karl Ove Moene in Alternatives to Capitalism, p. 85

One of the strengths of the causal-mechanisms approach to social explanation is how it responds to a very fundamental aspect of what we want explanations to do: we want to understand how something works. And a mechanisms account answers that question.

Let’s consider an example in detail. Suppose we observe that worker-owned cooperatives (WOC) tend to respond differently to price changes for their products than capitalist-owned firms (COF) when it comes to production decisions. The WOC firm will conform to this rule: “The higher the output price, the lower will be the supply” (85), whereas the COF firm will increase employment and supply. This is referred to as the Ward problem.

We would like to know how that comes about; what are the organization's processes and interactions that lead to the outcome. This means that we need to dig deeply into the specific processes that lead to production and employment decisions in both kinds of enterprises and see how these processes lead to different results.

The key part of the explanation will need to involve an analysis of the locus of decision-making that exists within the enterprise, and a demonstration of how the decision-making process in a WOC leads to a different outcome from that involved in a COF.

Here is how Karl Ove Moene analyzes this problem in “Strong Unions or Worker Control?” (Alternatives to Capitalism).

A production cooperative with worker control is defined somewhat restrictively as follows:

1. Productive activities are jointly carried out by the members (who in this case are the workers).
2. Important managerial decisions reflect the desires of the members, who participate in some manner in decision making.
3. The net income (income after expenses) is divide among the members according to some formula.
4. The members have equal rights, and important decisions are made democratically by one person, one vote. (84)

A capitalist firm acts differently:

1. Productive activities are carried out by wage laborers and directed by management controlled by the owners.
2. Important managerial decisions reflect the desires of the owners of the enterprise. 
3. Producers are paid a wage set by the labor market. The net income is assigned as profits to the owners.
4. Producers have no right of decision-making in production decisions.

The assumption is that decision-makers in both settings will make decisions that maximize their income — in other words, narrow egoistic economic rationality. In the assumptions used here for the cooperative, this implies that decision-making will aim at adjusting employment and production to the point where "marginal productivity (VMP) equals the net income per member (NIM)” (85). These quantities are represented in the graph above. Here is the reasoning:

What happens if the output price increases? In real terms, net income per member increases, because the fixed costs deflated by the output price decreases. Hence the NIM curve in Figure 5.1 shifts upwards, while the marginal productivity curve remains in place. As a consequence, the optimal number of members in the coop decreases and the firm's supply decreases the higher the output price. [Hence the coop lays off excess workers.] (85-86)

(Actually, this is what should happen in the long term. Moene goes on to show that the coop would not behave this way in the short run; but he acknowledges that the economic reasoning is correct. So for the sake of my example, let's assume that the coop behaves as Ward argues.)

The mechanism that distinguishes the behavior of the two kinds of firm is easy to specify in this case. The mechanism of individual decision-making based on rational self-interest is in common in the two types of firms. So the explanation doesn't turn on the mechanism of economic rationality per se. What differs across the cases is the collective decision-making process and the interests of the actors who make the decisions in the two cases. The decision-making mechanisms in the two cases are reflected in principles 2-4. The coop embodies a democratic social-choice rule, whereas the capitalist firm embodies a dictatorship choice rule (in Kenneth Arrow's sense -- one actor's preferences decide the outcome). A democratic decision about production levels leads to the reduction-of-output result, whereas a dictatorship decision about production levels leads to the increase-of-output result in these circumstances. And in turn, we are able to say that the phenomenon is explained by reference to the mechanism of decision-making that is embodied in the two types of firms -- democratic decision making in the coop and autocratic decision making in the capitalist firm.

This is a satisfying explanation because it demonstrates how the surprising outcomes are the foreseeable results of the differing decision processes. It identifies the mechanisms that lead to the different outcomes in the different circumstances.

This example also illustrates another interesting point -- that a given mechanism can be further analyzed into one or more underlying mechanisms and processes. In this case the underlying mechanism is the postulated model of action at the individual level -- maximizing of self-interest. If we postulated a different action model -- a conditional altruism model, for example -- then the behavior of the system might be different.

(I think this is a valid example of a mechanisms-based social explanation. Others might disagree, however, and argue that it is actually a deductivist explanation, reasoning from general characteristics of the "atoms" of the system (individual actors) to aggregate properties (labor-expelling collective decisions).)

Mechanisms and methodology

In its origin the causal mechanisms approach (link) is chiefly an answer to the question, “what is a good social explanation?”. So it turns out that much of the mechanisms discussion has taken place within the philosophy of science, especially the philosophy of social science and the philosophy of biology. The question I’d like to formulate here is whether mechanisms theory has any relevance to methodology as well? Can sociologists make better progress on concrete research problems by organizing some of their thinking around the construct of a social mechanism?

This kind of question comes up with respect to a number of the topics and innovations that have occurred in the philosophy of social science in recent years — critical realism, causal powers, and strategic fields, for example. It is certainly worthwhile developing theories and refinements of each of these concepts within the philosophy of social science. But it is an additional question to ask whether these concepts have a valuable role to play in discussions of research methodology and design as well.

So what is the problem of methodology, from the point of view of the working sociologist? The researcher has a number of preliminary tasks: What is the domain of social phenomena that are of interest? How can those phenomena be studied using available empirical tools? How can we theorize what is going on in this domain? How can we think about the nature of the entities, processes, causes, and meanings that make up this domain? And how can we probe the properties and dynamics of those sociological entities and processes?

Take a phenomenon like corruption. China is said to face a social and political problem deriving from widespread corrupt practices. How would we investigate the phenomenon of corruption in China (or India, the United States, or Finland)? Corruption is an umbrella concept that describes patterns of behavior across a wide range of domains: interactions between police and the public, practices through which business contracts are secured, enforcement of environmental and safety regulations, enforcement of trade regulations, practices through which individuals secure services from hospitals and licensing authorities, and there are indefinitely many other examples. Moreover, we can identify similar patterns of behavior in many countries, so there is an element of international comparison in play as well.

And yet not all instances of rule breaking are instances of corruption. So there is a preliminary task for the researcher, to engage in conceptual work and to define, for the purpose of the research enterprise, what kinds of behavior by agents and citizens will be counted as “corrupt”. Here we would like the researcher to work like a philosopher of language in some ways: “What do we mean by ‘X’ in ordinary or technical parlance?” In the current example, we would like the researcher to arrive at a working specification of corruption that is both reasonably practicable in application but also reasonably conformant to our prior assumptions about the category. (A definition of “corruption” that identifies corruption as “income-enhancing strategies by an economic actor” may be easy to apply but entirely inadequate as a specification of what we mean by corruption.) Robert Klitgaard does this kind of conceptual work in his 1988 and 1989 books, Controlling Corruption and Corrupt Cities: A Practical Guide to Cure and Prevention.

So let’s say we’ve offered a specification of corruption along these lines:

“[One species of] corruption involves situations in which individuals with decision-making power with respect to rules, fines, approvals, or contracts expects and receives covert payments from the consumer in exchange for the desired decision.”

This definition would capture many of the examples provided above: police officers giving speeding tickets, customs inspectors closing their eyes to valuable undeclared items, hospital staff making decisions about admissions and treatment of patients, safety inspectors approving a given location or activity — in exchange for a gift from the affected individual. Essentially the corrupt agent is “selling” a service or benefit which he or she controls to an individual who needs that service, contrary to the rules of the organization.

Now the researcher needs to specify a research question. It might be descriptive:

• "How frequent are instances of corrupt behavior by this description in setting X?"

It might be comparative:

• “How does institution X compare with institution Y with respect to the frequency of corrupt behavior by its agents?”

It might be explanatory:

• "Why do some institutions have higher rates of corrupt behavior than others?”

Or it might be policy-oriented:

• “What features of institutions can be introduced to reduce rates of corrupt behavior by the agents of the institution?”

The mechanisms theory is particularly relevant to methodology for at least the final three tasks. The background assumptions the researcher brings to his or her work about what a good explanation, a good policy design, or a good comparison ought to look like will strongly affect the ways in which he or she proceeds from this point further.

If the researcher adopts the simple empiricist model of explanation — find characteristics that appropriately co-vary with the dependent variable — then the research path is fairly clear:

• Identify a set of cases (don’t select on the dependent variable) and see whether there are correlations among institutional features and rates of corruption. (Ultimately this seems to be the prescription of King, Keohane, and Verba in Designing Social Inquiry: Scientific Inference in Qualitative Research.)

Or he or she might pursue the necessary-and-sufficient-condition version of the approach:

• Identify a set of cases (again with provisos about selection of cases) and see whether we can identify necessary and/or sufficient conditions using Mill’s methods or other analytical tools. (Gary Goertz describes strategies like these in Necessary Conditions: Theory, Methodology, and Applications.)

On the other hand, if the researcher adopts the causal-mechanisms approach — identify causal mechanisms and processes that affect the occurrence or frequency of the outcome of interest — then he or she will proceed differently. The researcher will examine the individual cases carefully, looking to identify the factors and mechanisms that appear to be involved in the outcomes of interest; he or she will then look to see whether there are common processes involved in multiple cases; and he or she will consider whether available theories of social processes are relevant to the explanation of the outcomes observed. (This is essentially the method pursued by McAdam, Tarrow, and Tilly in Dynamics of Contention.)

For example, the extensive theorizing and discussions of principal-agent problems in political science may shed light on concrete mechanisms through which corrupt behaviors are controlled in a variety of existing circumstances. The Principal wants the Agent to act according to the rules of the organization; the Agent is to some extent outside his observation and control. So what mechanisms of self-enforcement are available to lead the Agent to comply with the expectations of the Principal?

One mechanism of compliance that the Principal may consider is a Corrupt Practices Tipline, whereby consumers can anonymously report corruption by specific officers. This extends the Principal’s ability to gather information about the Agent’s behavior. The Agent, knowing that the Tipline exists, constrains his otherwise corrupt inclinations, and the incidence of corrupt practices declines.

Another possible approach for the Principal is to link the Agent's longterm rewards to his/her longterm success in assigned tasks. Jean Ensminger describes the practice of gifts of "bridewealth" in these terms, as a way in which cattle owners maintain the loyalty of their herders during the long periods of time that they are out of sight in the foraging areas (Making a Market: The Institutional Transformation of an African Society) Deferred compensation and stock options may play a similar role in the modern business organization.

Another mechanism that might be considered is selective investigation and enforcement. The Principal may know that many customs agents are accepting small gifts of money when evaluating customs declarations, and that a small number of these transactions involve high-value items and correspondingly high-value gifts. It might be sensible to focus investigation and enforcement on this smaller incidence of high-value transactions. Choosing this strategy may have the effect of significantly reducing “big corrupt transactions” while leaving “small corrupt transactions” essential unchanged.

A final mechanism that might be considered here (out of many possible avenues of investigation) is a cultural factor -- training, education, and inculturation. We might consider whether one cultural setting does a better job of preparing individuals to play honest roles in organizations than another based on the educational and formative experiences that are offered to them. This can provide the basis for a hypothesis about a causal mechanism leading to a high (or low) rate of corrupt behavior; and it might provide a basis for a possible policy intervention (workplace training to shift basic values).

This is one example of the way a concrete research strategy might evolve. The important point of the example is that the philosophical orientations described here — “simple empiricism”, “mechanisms theory” — lead researchers to structure their investigations in very different ways. The researcher who is attuned to causal mechanisms will focus his or her efforts on uncovering the concrete social pathways or processes through which a given pattern of behavior is either encouraged or discouraged; and the researcher will be led to consider comparative cases to see whether similar arrangements lead to similar patterns of behavior in the other cases. This suggests that the discussion of the ins and outs of causal mechanisms theory in philosophy of social science may in fact be an important contribution to social science methodology as well.

Mechanisms and powers

source: William Bechtel, Discovering Cell Mechanisms: The Creation of Modern Cell Biology

The causal-powers approach to the understanding of causation is sometimes presented as an exclusive alternative to both traditional regularity theories and to more recent causal mechanism theories. In an earlier post I discussed Ruth Groff’s contributions to this topic. Here I would like to present a provocative view: that the causal mechanisms and causal powers are complementary rather than contradictory. The causal mechanisms theory benefits by being supplemented by a causal powers theory and the causal powers theory benefits by being supplemented by a causal mechanisms theory. In other words, the two theories are not exclusive alternatives to each other, but rather serve to identify different parts of the whole of causation.

The causal powers theory rests on the claim that causation is conveyed from cause to effect through the active powers and capacities that inhere in the entities making up the cause. The causal mechanisms theory comes down to the idea that cause and effect are mediated by a series of events or interactions that lead (typically) from the occurrence of the cause to the occurrence of the effect. In other words, cause and effect are linked by real underlying causal sequences (often repeatable sequences).

My thesis of the mutual compatibility of powers and mechanisms goes along these lines. If we press down on a putative mechanisms explanation, we are led eventually to postulating a set of causal powers that provide the motive force of the postulated mechanisms. But equally, if we press down on the claim that a certain kind of entity has a specified causal power or disposition, we are led to hypotheses about what mechanisms are set in play be its constituents so as to bring about this disposition.

Begin with a causal mechanism story:

• C => {x happens bringing about y, bringing about z, bringing about u, which is E} => E

How is it that the sub-links of this chain of mechanism pieces happen to work to bring about their consequent? We seem to have two choices: We can look to discover a further underlying mechanism; or we can postulate that the sub-link entity or structure has the power to bring about its consequent. So if we push downward within the terms of a mechanism explanation, one way to close the story is by postulating a causal power at some level.

Now start with a causal power claim. Suppose we assert that:

• Salt has the causal power of making H2O electrically conductive when dissolved.

Is this simply an unanalyzable fact about salt (or saline solution)? It is not; instead, we can look downward to identify the physical mechanisms that are brought into play when salt enters solution in H2O. That mechanism is well understood: the Na+ and Cl- ions created by the dissolution of salt permit free electrons to pass through the solution.

So we can explain the causal power by discovering the causal mechanism that gives rise to it; we explain links in the putative mechanism by alluding to the powers of the entities involved at that stage; and we can explain other things by referring to the causal powers that we have discovered to be associated with various kinds of things and structures.

If we take this set of possibilities seriously, then powers and mechanisms are answering different questions within the causal nexus. The reference to powers answers the question, “What does x do?”, while the reference to mechanisms answers the question, “How does x work?"

From a scientific point of view, it is always legitimate to ask how the powers of an entity or structure come to be in the natural world. What is it about the micro-structure of the thing in virtue of which the thing’s properties are established? In fact, this is one of the key intellectual challenges of the sciences. And this is a request for specification of some of the mechanisms that are at work. But likewise, it is always legitimate to ask what gives force to a given mechanism; and here we are eventually driven back to the answer, “some of the components of the mechanism have X, Y, Z powers to affect other entities” without further analysis within that particular explanation.

One might imagine that there are primitive causal powers — powers attached to primitive particles that have no underlying components or mechanisms.  We might begin to give a list of primitive causal powers: mechanical interactions among physical objects (transfer of momentum from one particle to another); electromagnetic properties inhering in one object and creating forces affecting other objects; gravitational forces among objects possessing mass; the causal interactions that occur within the central nervous system. And we might seek to demonstrate that all causal powers depend on combinations of these sorts of "primitive" causal powers -- a kind of Hobbesian materialism.  But this is needlessly strenuous from a metaphysical point of view. Better is to consider the middle-level range of powers and mechanisms where we are able to move upwards and downwards in our search for underlying causal mechanisms and supervening causal powers.

This line of thought suggests that questions about the metaphysics of causation are perhaps less pressing than they are sometimes made out to be. A thing's powers are not irreducible attributes of the thing; rather, they are the orderly consequence of the composition of the thing and the causal properties of those components and their interactions. It is hard to see that much turns on whether we think of the world as consisting of entities with powers, or as composites with system properties created by their components. The key question seems to be something like this: what is implied when we make a causal assertion? Both CP and CM agree that the core implication is the idea that one event, structure, or condition brought about the occurrence of another event, structure, or condition.  And the languages of both powers and mechanisms do a pretty good job of expressing what we mean in asserting this implication.

(John Dupré takes a similarly ecumenical view about several approaches to the theory of causation in a recent article, "Living Causes", where he advocates for what he calls "causal pluralism"; link. He writes: "I believe that causality is a complex and diverse set of phenomena, and most or all of these accounts provide valuable and complementary perspectives on the topic. Such a pluralistic view is quite a common one among contemporary philosophers; however there are significant differences in the form that such pluralisms can take" (20). On the mechanisms side within the philosophy of biology is William Bechtel's Discovering Cell Mechanisms: The Creation of Modern Cell Biology, who writes: "Beginning in the 1940s an initially small cadre of investigators who were pioneers in the modern discipline of cell biology began to figure out the biochemical mechanisms that enable cells to perform these functions. although miniaturized, the mechanisms they found to be operative in each cell are staggeringly complex" (1 ).)

Causal powers from a metaphysical point of view

A number of scholars who are interested in causation have recently expressed new interest in the concept of causal powers. This makes sense in a very straightforward and commonsensical way. But it also raises some difficult questions about metaphysics: how are we to think about the underlying nature of reality such that things, events, or conditions have "causal powers"? These questions raise issues that a number of talented philosophers are now taking on in a systematic way. Particularly interesting are recent writings by Ruth Groff, who represents a wave of contemporary thinking in metaphysics that aims to revitalize portions of Aristotle's views of causation in opposition to Hume's.

Groff's work on causal powers is sustained over a number of recent works, including especially her 2012 book Ontology Revisited: Metaphysics in Social and Political Philosophy (Ontological Explorations), her introduction and chapter in Greco and Groff, eds., Powers and Capacities in Philosophy: The New Aristotelianism, and her contribution to Illari, Russo, and Williamson, Causality in the Sciences. Groff emphasizes a broad clash of perspectives between a Humean theory of causation ("constant conjunction, no necessary relations among things or events") and a neo-Aristotelian theory ("things have powers, powers underlie causal relations among things and events"). Here is how she and Greco put the perspective of the "New Aristotelianism" in Powers and Capacities:

Humeanism is now under serious pressure within analytic metaphysics. In particular, after having been dismissed for generations as so much antiquated animism, the loosely-Aristotelian theorizing of real causal powers has now come to be a major focus of research within the specialty. (kl 204)

Moreover, Groff believes that American social sciences are still largely in the grip of the Humean metaphysics.  In "Getting Past Hume" in Causality in the Sciences, she writes:

One can't help but wonder what the outcome would actually be, were there to be a floor-fight on the question, i.e., a substantive debate within analytic philosophy and methodology of social science on the merits of Humean anti-realism about causality versus the merits of a powers-based, realist account of causality.

...

What is significant about all of this for my own argument is not so much that Humeanism continues to be the default ontology of especially American, often positivist, social science; but rather that it can be combined with the idea that it is not -- i.e., with the idea that competing versions of regularity theory somehow differ in a deep way, or that it is possible to remain neutral on what causality is, whilst engaging in causal explanation.

This poses a stark contrast; either you are positivist, anti-realist, and Humean or you are anti-positivist, realist, and neo-Aristotelian.  However, it is worth observing that there seem to be two currents of realist thought that reject Humean causation, not just one: the powers ontology that Groff (and Mumford and Anjum in Getting Causes from Powers) advocate; and the causal-mechanisms approach that has been advocated by philosophers and sociologists such as Hedstrom, Elster, and Ylikoski under the broad banner of analytical sociology. One might take the view that the causal-mechanisms approach ultimately requires something like the powers ontology -- "How else are we to account for the fact that sparks cause gasoline to explode?"; but on its face, these are two fairly independent realist responses to Hume. And certainly it is difficult to find a neo-Aristotelian predilection among the causal-mechanism advocates.

Groff takes up causal mechanisms theory in "Getting Past Hume" in  Causality in the Sciences. She concedes that this approach -- in the hands of Jon Elster and in my own writings, for example -- claims to be realist and anti-positivist, in that it rejects the notion that explanation depends on the discovery of general laws. But she doesn't think that the causal-mechanisms approach actually succeeds in presenting a substantive alternative to the Humean framework on causation: "Upon closer examination, the mainstream mechanisms model is more of the same, metaphysically."

Fleshing out her argument, she seems to be arguing that causal-mechanisms theory can either retreat to constant conjunction (at the level of the linkages of individual causal mechanisms) or it can press forward to a causal powers interpretation; there is no third possibility. "As with the other models, nothing on the mainstream mechanisms model is in a position of actually doing anything, in the sense of actively producing an effect. Thus here too, with an extra bit of ironic panache, the explanation-form functions as a delivery mechanism (no pun intended) for a Humean metaphysics." And it is true that most definitions of causal mechanisms make some kind of reference to regularities and repeatability.

My own formulation of the mechanisms theory is one of the targets of Groff's critique. And in fact I can reconstruct my reasons for thinking that mechanisms need to involve some kind of regularities; and I don't think it implies a collapse onto Humean causation. (At one point I wanted to call them "pocket regularities", to distinguish them from the grand social or psychological laws that Hempel and Mill seemed to want to discover.)  I wanted to assert that:

"M [information diffusion] is the mechanism connecting E [police beating] with O [rapid mobilization of an angry crowd]" is a description of a real underlying (perhaps unknown) causal process through which the features of E bring about the occurrence of O.

This is an ontological claim and it is a realist claim. But there is also an epistemic issue: How would we know that M is indeed such an underlying reality? It seems unavoidable that we would need to either produce empirical evidence supporting the conclusion that M frequently conveys these kinds of effects in these kinds of circumstances (the approach Tilly takes) or we need to have a theory of the mechanism which accounts for how it works to bring about the effect. The first boils down to a discovery of a limited set of regularities in a range of circumstances; the latter is a theoretical demonstration of how it works.  So this way of conceptualizing mechanisms does indeed invoke regularities of some sort.  However, it doesn't agree with the Humean idea that causation is nothing but regularities or constant conjunction. The regularities that are invoked are symptoms of the underlying causal mechanism, not criterial replacements for the mechanism.

Moreover, the powers theory seems to be subject to the same possible objection: how do we know that lightning has the causal power of starting barns on fire, unless we have repeatedly observed the chain of events leading from lightning strike to blaze?

Another thing that demands more attention is an assumption about the implications of the "realism" of powers. What follows from the idea that things have real causal powers? Groff puts the view in these terms: to assert that powers are real is to assert that they are irreducible (kl 204). But that seems questionable. We may think that feudalism was real, while at the same time thinking that its properties and dynamics derived from more fundamental social relations that compounded to create the distinctive dynamics of feudalism. So it doesn't seem that realists have to also accept the idea of irreducibility of the things about which they are realist. Or to put the point the other way around: the idea that realism implies irreducibility appears to also imply a fairly strong thesis about emergence. Groff returns to this set of ideas in Ontology Revisited, chapter three: "An emergent phenomenon (property or entity) is one that is not equivalent, ontologically, to the plurality of its parts." And here too she emphasizes irreducibility. But, as Poe Yu-ze Wan shows in "Emergence a la Systems Theory: Epistemological Totalausschluss or Ontological Novelty?" in Philosophy of the Social Sciences, philosophers have differed on the question of whether "emergence" implies "irreducibility" (link). The theory of emergence offered by Mario Bunge does not require irreducibility.

One thing I particularly like about Groff's work on causal powers is her persistence in working through the logical and conceptual implications of this field. She is painstaking in her effort to discover the implications of various parts of the several theories of causation (and freedom of the will in other essays); and this is exactly how we make progress on difficult philosophical issues like these.

Causal concepts

source: D. Little, “Causal Explanation in the Social Sciences,” Southern Journal of Philosophy (1995) (link)

It may be useful to provide a brief account of some of the key ideas that are often invoked in causal explanations in the social sciences. (Here is an earlier post that summarized some current issues in causation research; link. And here are several earlier articles on causal explanation; link, link, link.)

The general idea of a social cause (X causes Y) goes along these lines: X is a structure or feature of social life that varies across social settings and whose presence increases the likelihood of occurrence of Y. The presence of X (perhaps in the presence of Y and Z as well) contributes to processes leading to Y.

This simple formulation contains several hidden assumptions -- most importantly, that outcomes have causes, that causes retain their characteristics over time and across instances, and that there are processes or dynamics within the domain of things and processes that convey with some form of necessity one set of circumstances and events onto another.

An example

For example, consider this hypothetical narrative describing a riot in a European city with a large community of impoverished immigrant people:

• (C1) simmering resentment by immigrant youth of joblessness and low social esteem
• (C2) heat wave creating discomfort and misery in crowded neighborhoods
• (C3) chronic disrespectful and rough police treatment of immigrant youth
• (I) forceful arrest of mis-identified young person in a city park, leading to serious injury of the youth
• (O) several days of rioting occur

The associated causal hypothesis goes along these lines: In the context of simmering resentment by immigrant youth and a pattern of mistreatment by police, feelings in the community were unusually elevated by the heat wave. When the arrest occurred a small protest began in the park, which spread to other blocks in the city and eventuated in the burning of cars, smashing of shop windows, and multiple further arrests.

Conditions Ci are standing conditions that played a causal role in the occurrence of the riot. The arrest incident was the instigating event, the match that ignited the social "gasoline". If any of C1, C2, C3 had been changed six months earlier, it is unlikely that O would have occurred. Each was necessary for I leading to O in the circumstances of the day.  If C1, C2, C3 are present, it is likely that some instigating event will occur in the normal hustle-bustle of urban life. I was the instigating condition. For researchers seeking general explanations of urban unrest, C1 and C3 appear to be strong candidates for common causes across many examples of urban riots. Two mechanisms are invoked here: a mechanism having to do with the individual's propensity to engage in protest ("resentment and mistreatment elevates propensity to protest") and a mechanism having to do with the spread of protest ("a small disturbance between a few teenagers and the police escalates through direct contact with other disaffected individuals through the neighborhood").

Here are brief discussions of many of the concepts that are commonly invoked in discussions of social causation.

Causal narrative

An organized and temporally directed account of the occurrence of an event or change, identifying the conditions, circumstances, and events that were causally relevant to its occurrence. A narrative needs to provide empirical evidence for its empirical claims and theoretical justification for the causal mechanisms and processes it postulates.

Standing condition

A condition or circumstance that persists through an extended period of time and that serves as part of the necessary causal background of a given causal process or mechanism. Persistent racial isolation is a standing condition in many explanations of the effects of inner city poverty.

Instigating event

An instigating event is an occurrence, including change of state of some background property, that triggers a change in some other property or process. The early-morning arrest by patrons of a blind pig (unlicensed tavern) in Detroit was the instigating event of the 1967 Detroit riot/uprising.

Necessary condition

A condition that must be present in order for a given causal interaction to occur. "If X had not been present, the outcome O would not have occurred."

Sufficient condition (conjunction of conditions)

A condition (or conjunction of conditions) whose presence suffices to bring about the outcome. "If X&Y&Z were present, then O would have occurred."

Counterfactual statements

It is worth underlining the point that necessary and sufficient conditions invoke counterfactual statements: If X had not occurred, Y would not have occurred. The logic of counterfactuals (modal logic) has a controversial and unresolved history. But given that causal language always implies some kind of necessity, we cannot dispense with counterfactuals and still have an adequate causal vocabulary.

INUS condition (J. L. Mackie)

J.L. Mackie's work on causation in The Cement of the Universe: A Study of Causation brought to closure a long line of thought about the logic of causal relations, culminating in his concept of INUS conditions. Consider this complex causal statement about the circumstances causing P:

'All (ABC or DGH or JKL) are followed by P' and 'All P are preceded by (ABC or DGH or JKL)' (Mackie, 62)

Mackie then defines an INUS condition:

Then in the case described above the complex formula '(ABC or DGH or JKL)' represents a condition which is both necessary and sufficient for P: each conjunction, such as 'ABC', represents a condition which is sufficient but not necessary for P. Besides, ABC is a minimal sufficient condition:  none of its conjuncts is redundant: no part of it, such as AB, is itself sufficient for P. But each single factor, such as A, is neither a necessary nor a sufficient condition for P. Yet it is clearly related to P in an important way: it is an insufficient but non-redundant part of an unnecessary but sufficient condition: it will be convenient to call this … an inus condition. (62)

To simplify:

A is an INUS condition for P if for some X and Y, (AX v Y) is a necessary and sufficient condition for P, but A is not sufficient for P and X is not sufficient for P.

Causal mechanism

An interlocked series of events and processes that, once initiated by some set of conditions, [usually] brings about a given outcome O. The idea that there are real mechanisms embodied in the "stuff" of a given domain of phenomena provides a way of presenting causal relations that serves as a powerful alternative to the "regularity" view associated with Hume. "Poor performance on standardized tests by specific groups is caused by the mechanism of stereotype threat" (Claude Steele, Whistling Vivaldi: How Stereotypes Affect Us and What We Can Do (Issues of Our Time)). This mechanism is a hypothesized process within the cognitive-emotional system of the subjects of the test. (James Mahoney's survey article on the mechanisms literature is a good introduction to the debate; link.)

Causal powers

The idea that certain kinds of things (metals, gases, military bureaucracies) have internal characteristics that lead them to interact causally with the world in specific and knowable ways. This means that we can sometimes identify dispositional properties that attach to kinds of things. Metals conduct electricity; gases expand when heated; military bureaucracies centralize command functions. (Harre and Madden, Causal Powers: Theory of Natural Necessity)

Probabilistic causal relation

A relationship between A and O such that the occurrence of A increases/decreases the likelihood of the occurrence of O. This can be stated in terms of conditional probabilities: P(O|A) ≠ P(O) [the probability of O given A is not equal to the probability of O]. For a causal realist, the definition is extended by a hypothesis about an underlying causal mechanism. [Smoking is a probabilistic cause of lung cancer [working through physiological mechanisms X,Y,Z]. This is equivalent to Wesley Salmon's criterion of causal relevance (Scientific Explanation and the Causal Structure of the World).

Causal explanation of a singular event

When we are interested in the explanation of a single event, a causal narrative leading up to that event is generally what we are looking for. What led to the outbreak of World War I? Why did Khomeini come to power in Iran in 1979? There are generally two difficult problems facing a proposed causal-narrative explanation of a singular event. First, we need to somehow empirically validate the claims about causal mechanisms and processes that are invoked in the narrative. But since this is a singular event, we do not have the option of using experimental methods to empirically test the claim "X leads by mechanism M to Y" that the narrative proposes. This is one important reason why mechanism theorists have generally required that specified mechanisms have roughly similar causal properties in a range of circumstances. Circumstances embodying the core features of a public goods problem usually lead to elevated levels of free riding -- whether in public radio fundraising, strikes, classroom discussions, or rebellions. Second, there is the problem of alternative realizability and multiple causal pathways leading to the same outcome. If the conditions leading to World War I were sufficiently ominous, then whether the assassination of the Archduke or some other event brought it about is of less explanatory importance. Given that potential instigating events occur with a certain probability, some event would have occurred within those few months that led to war. So it is better to identify the standing conditions that made war likely as the causes, rather than the assassination of the Archduke.

Generalizations about the causes of a kind of social entity or event

We are often interested in answering causal questions about classes of events: Why do peasant rebellions occur? Why does corruption rise to such high levels in many cities? Why do democracies not wage war against each other? Here we are looking for common conjunctions of causal factors that can be shown to be causally relevant in many such events. It is possible that we will discover that peasant rebellions do not have a single set of causal antecedents; rather there are multiple profiles of peasant rebellions, each with a set of causal conditions significantly different from the other profiles.

Methods of causal inquiry

How can social researchers identify causal relations among social events and structures? There are several groups of methods that social scientists and historians have employed: statistical-causal models, small-N models based on Mill's methods of similarity and difference (link, link), and case studies and process-tracing methods through which researchers seek to identify and confirm causal relations in individual cases. In each case the method derives from fundamental ideas about the nature of causation: the idea that causal relations between several factors give rise to statistical regularities when we have a large number of cases; the idea that we can use the features of necessary and sufficient conditions to select cases in order to include or exclude certain factors as causally related to the outcome; and the idea that causal mechanisms and processes can often be observed fairly directly in the historical record (Alexander George and Andrew Bennett, Case Studies and Theory Development in the Social Sciences).