A causal narrative?

source: Edward Tufte, edwardtufte.com

In a recent post I referred to the idea of a causal narrative (link). Here I would like to sketch out what I had in mind there.

Essentially the idea is that a causal narrative of a complicated outcome or occurrence is an orderly analysis of the sequence of events and the causal processes that connected them, leading from a set of initial conditions to the outcome in question. The narrative pulls together our best understanding of the causal relations, mechanisms, and conditions that were involved in the process and arranges them in an appropriate temporal order. It is a series of answers to "why and how did X occur?" designed to give us an understanding of the full unfolding of the process.

A narrative is more than an explanation; it is an attempt to “tell the story” of a complicated outcome. So a causal narrative will include a number of causal claims, intersecting in such a way as to explain the complex event or process that is of interest. And in my view, it will be a pluralistic account, in that it will freely invoke a number of causal ideas: powers, mechanisms, necessary and sufficient conditions, instigating conditions, and so forth.

Here is how I characterized a historical narrative in New Contributions to the Philosophy of History:

What is a narrative? Most generally, it is an account of the unfolding of events, along with an effort to explain how and why these processes and events came to be. A narrative is intended to provide an account of how a complex historical event unfolded and why. We want to understand the event in time. What were the contextual features that were relevant to the outcome — the settings at one or more points in time that played a role? What were the actions and choices that agents performed, and why did they take these actions rather than other possible choices? What causal processes—either social or natural—may have played a role in bringing the world to the outcome of interest? (29)

We might illustrate this idea by looking at the approach taken to contentious episodes and periods by McAdam, Tarrow, and Tilly in Dynamics of Contention. In their treatment of various contentious periods, they break the given complex period of contention into a number of mechanisms and processes, conjoined with contingent and conjunctural occurrences that played a significant causal role in the outcome. The explanatory work that their account provides occurs at two levels: the discovery of a relatively small number of social mechanisms of contention that recur across multiple cases, and the construction of complex narratives for particular episodes that bring together their understanding of the mechanisms and processes that were in play in this particular case.

We think what happens within a revolutionary trajectory can better be understood as the result of the intersection of a number of causal mechanisms. We do not offer a systematic account of all such mechanisms and their interaction in a sample of revolutionary situations. Instead, we use a paired comparison of the Nicaraguan revolution of 1979 and the Chinese student rebellion of 1989 to zero in on one processes in particular: the defection of significant elements from a dominant ruling coalition. (kl 2465)

The narrative for a particular case (the Mau Mau uprising, for example) takes the form of a chronologically structured account of the mechanisms that their analysis identifies as having been relevant in the unfolding of the insurgent movement and the government's responses. MTT give attention to "episodes" within larger processes, with the clear implication that the episodes are to some degree independent from each other and are amenable to a mechanisms analysis themselves. So a narrative is both a concatenated series of episodes and a nested set of mechanisms and processes.

Robert Bates introduces a similar idea in Analytic Narratives under the rubric of “analytic narrative”. The chief difference between his notion and mine is that his account is limited to the use of game theory and rational choice theory to provide the linkages within the chronological account, whereas I want to allow a pluralistic understanding of the kinds and levels of causes that are relevant to social processes.

Here is a brief account of what Bates and his collaborators mean by an analytic narrative:

The chapters thus build narratives. But the narratives are analytic narratives. By modeling the processes that produced the outcomes, we seek to capture the essence of stories. Should we possess a valid representation of the story, then the equilibrium of the model should imply the outcome we describe—and seek to explain. Our use of rational choice and game theory transforms the narratives into analytic narratives. Our approach therefore occupies a complex middle ground between ideographic and nomothetic reasoning. (12)
...
As have others, however, we seek to return to the rich, qualitative, and descriptive materials that narratives offer. And, as have others, we seek an explicit and logically rigorous account of the events we describe… We seek to locate and explore particular mechanisms that shape the interplay between strategic actors and that thereby generate outcomes. Second, most of these [other] literatures are structural: they focus on the origins and impact of alignments, cleavages, structures, and institutions. Our approach, by contrast, focuses on choices and decisions. It is thus more micro than macro in orientation. By delineating specific mechanisms and focusing on the determinants and impacts of choices, our work differs from our predecessors. (12-13)

A narrative typically offers an account of an historically particular event or process: the outbreak of a specific war, the emergence of ethnic conflict at a specific place and time, or the occurrence of a financial crisis. This places narratives on the side of particular social-science analysis. Is there a role for generalization in relation to narratives? I think that MTT would suggest that there is not, when it comes to large event groups like revolutions. There is no common template of revolutionary mobilization and regime collapse; instead, there are local and national interactions that constitute recurring mechanisms, and it is the task of the social scientist to discover the linkages and contingencies through which these various mechanisms led to revolution in this case or that. MTT try to find a middle ground between particularity and generalization:

Have we only rediscovered narrative history and applied to it a new, scientistic vocabulary? We think not. While convinced of the futility of deducing general covering laws of contention, we think our program -- if it succeeds -- will uncover recurring sets of mechanisms that combine into robust processes which, in turn, recur over a surprising number and broad range of episodes. (kl 3936)

In my view, anyway, a narrative describes a particular process or event; but it does so by identifying recurring processes, mechanisms, and forces that can be discerned within the unfolding of the case. So generalizability comes into the story at the level of the components of the narrative -- the discovery of common social processes within the historically unique sequence of events.

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 ).)

Causality and metaphysics

Advocates of the causal powers approach attach a great deal of importance to the metaphysics of causation -- the sorts of properties and relations that we attribute to the kinds of things that we want to postulate. The neo-Aristotelian point of view represented by Ruth Groff and others appears to have metaphysical objections to the causal-mechanisms approach: the CM approach postulates the wrong kind of relations among entities, according to this group. So if I want to argue that mechanisms and powers are compatible, as I do, then I need to take into account the metaphysical arguments. It will be necessary to tell a story about the nature of the world that gives a place and meaning to the metaphysical premises of each theory.

The possibility of fundamental metaphysical incompatibility cannot be trivially ruled out. Consider this different kind of example: the distance between the premises of analytical Marxism and the neo-Hegelian theory of internal relations espoused by Bertell Ollman in Alienation: Marx's Conception of Man in Capitalist Society (link). Even if there were the possibility of some degree of convergence in conclusions about capitalism -- e.g. the likelihood of recurring crises -- the two schools of thought differ fundamentally on the nature of social entities and structures. They differ in terms of their social metaphysics. Analytical Marxists take the view that the structures of capitalism are the composite effect of variously motivated individuals; so there is an underlying atomism in the ontology of AM. Causes are fully distinct from the things they affect. Ollman, by contrast, believes that we need to conceive of the structures and social relations of capitalism relationally: the wage labor relation is not an atomistic relation between capitalist and worker, but rather a mutually implicating set of relations between the two that cannot be fully separated. Here is a passage in which Ollman attempts to capture the distinctive features of Marx's social metaphysics:

What is distinctive in Marx's conception of social reality is best approached through the cluster of qualities he ascribes to particular social factors. Taking capital as the example, we find Marx depicting it as "that kind of property which exploits wage-labor, and which cannot increase except on condition of getting a new supply of wage-labor for fresh exploitation" (Marx and Engels, 1945, 33). What requires emphasis is that the relation between capital and labor is treated here as a function of capital itself, and part of the meaning of "capital". This tie is extended to cover the worker as well, where Marx refers to him as "variable capital" (Marx, 1958, 209). The capitalist is incorporated into the same whole: "capital is necessarily at the same time the capitalist . . . the capitalist is contained in the concept of capital" (Marx, 1973, 512). Elsewhere, Marx asserts that "the means of production monopolized by a certain section of society", "the products of laborers turned into independent powers", "money", "commodities" and even "value that sucks up the value creating powers" are also capital (Marx, 1959b, 794-5; Marx, 1958, 153; Marx, 571). What emerges from these diverse characterizations is a conception of many tied facets, whose sense depends upon the relations Marx believes to exist between its components: property, wage-labor, worker, his product, commodities, means of production, capitalist, money, value (the list can be made longer still). (Chapter 2, section ii)

This example demonstrates the possibility of a genuine and deep incompatibility between two social theories at the level of the assumptions they make about the nature of the world -- their metaphysical theories.

So what about causal powers and causal mechanisms? The primary metaphysical commitment that the CP theorists advocate derives from their treatment of powers and essences -- two characteristic ideas from Aristotle. A power is thought to inhere in a thing in a particularly deep way; it is not an accidental expression of the empirical properties of the thing but rather an essential and active expression of the nature of the thing. The causal powers theory comes down to the idea that things and structures have an active capacity to bring about certain kinds of effects. In Groff’s terms, things are not passive but rather active.

Here is how Tuukka Kaidesoja introduces the metaphysical framework of critical realism in relation to causality in Naturalizing Critical Realist Social Ontology. Kaidesoja finds that the concept of a causal power is fundamental to critical realism (105). A thing's power is the characteristic of the world through which causal influence arises; without the concept of causal power, we would indeed be stranded in a Humean world of pure constant conjunction. Kaidesoja quotes Harre and Madden in these terms:

"X has the power to A" means "X (will)/(can) do A, in the appropriate conditions, in virtue of its intrinsic nature". (Kaidesoja, 106)

So what about the metaphysics of the causal mechanisms theory? Generally speaking, advocates of the mechanisms approach have not been very interested in the metaphysical issues. They (we) are generally realist, so we postulate that there are real causal interactions. This is indeed a metaphysical position. But this family of thinkers tends to be mid-range realists: they want to understand the necessity of causal relations at one level as deriving from the real workings of the physical or social system a bit lower down; but they generally don't seem to want to pose the ultimate question: how could any event or structure exert causal influence on another? So the causal mechanisms theorists are perhaps better described as scientific realists rather than philosophical or critical realists. They take the view that the world has the properties (approximately) that our best scientific theories attribute to things. (Could we call them "Galilean realists"?)

Curiously enough, this contrast seems to have a lot to do with the quibble I raised for Ruth Groff in the earlier post: whether powers should be thought to be "irreducible". Scientific realists would say they are not irreducible; rather, we can eventually arrive at a theory (molecular, genetic, economic, psychological, rational choice, physical) that displays the processes and mechanisms through which the ascribed power flows from the arrangement and properties of the thing.

On this standpoint, powers are attributions we make to things when we don't know quite enough about their composition to work out the physics (or sociology) of the underlying mechanisms. They do attach to the entity or structure in question, surely enough; but they do so in virtue of the physical or sociological composition of the entity, not because of some inherent metaphysical property.

We might try to reconcile these two perspectives with a few simple ideas:

1. Entities and structures at a range of levels of being have causal powers: active capacities to influence other entities and structures.
2. Whenever we identify a causal power of a thing, it is always open to us to ask how this power is embodied; what it is about the inner constitution of the entity that gives it this power.
3. When we succeed in arriving at a good scientific answer to this question, we will have shown that the power in question is not irreducible; it is rather the consequence of a set of mechanisms set in play by the constitution of the entity.

So the discovery of a given causal power of a thing is not a metaphysical fundamental; it is rather an empirical scientific discovery that invites analysis into its underlying composition.

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).

Social causation

The idea of social causation is a difficult one, as we dig more deeply into it. What does it mean to say that "poor education causes increased risk of delinquency" or "population growth causes technology change" or "the existence of paramilitary organizations contributed to the rise of German fascism"? What sorts of things can function as "social causes" -- events, structures, actions, forces, other? What social interactions extend over time in the social world to establish the links between cause and effect? What kinds of evidence are available to support the claim that "social factor X causes a change in social factor Y"?

Helen Beebee, Christopher Hitchcock, and Peter Menzies' The Oxford Handbook of Causation is a valuable resource on topics involving the philosophy of causation, and several of the contributions are immediately relevant to current debates within the philosophy of social science.

Harold Kincaid considers a number of the hard questions about social causation in his contribution to the Handbook, "Causation in the Social Sciences". Perhaps most relevant to my ongoing concerns is his defense of non-reductionist claims about social causation. It is often maintained (by methodological individualists) that causal relations exist only among individuals, not among higher-level social entities or structures. (Elster and Hedstrom make claims along these lines in multiple places.) Kincaid rejects this view and affirms the legitimacy of macro- or meso-level causal assertions.

When a particular corporation acts in a market, it has causal influence. The influence of that specific entity is realized by the actions of the individuals composing it just as the influence of the baseball on the breaking window is realized by the sum of particles composing it. The social level causal claims pick out real causal patterns as types that may not be captured by individual kinds because multiple realizability is real. (kl 16102)

These arguments are a valuable antidote to the tendency towards reductionism to the level of individual activity that has often guided philosophers when they have considered the nature of social causation.

Phil Dowe's discussion of causal process theories is useful for the social sciences ("Causal Process Theories"). It is hard to think of the social world as an amalgam of discrete events; it is easier to think of a variety of processes unfolding, subject to a range of forces and obstacles.  Dowe gives much of the credit for current interest in causal process language to Wesley Salmon (along with resurrection of the idea of a "rope of causation" to replace that of a "chain of causation").

For Salmon the causal structure of the world consists in the nexus of causal processes and interactions. A process is anything with constancy of structure over time. (kl 4924)

The language of causal processes seems to fit the nature of social causation better than that of events and systems of billiard balls. And we have the makings of a metaphysics of process available in the social sciences, in the form of a stream of actions and reactions of individuals aggregating to recognizable social patterns. So when we say that "population increase stimulates technology innovation", we can picture the swarming series of interactions, demands, and opportunities that flows from greater population density, to rewards for innovation, to a more rapid rate of innovation.

Another useful contribution in the Handbook with special relevance to the social world is Stephen Mumford's contribution, "Causal Powers and Capacities."

The powers ontology accepts necessary connections in nature, in which the causal interactions of a thing, in virtue of its properties, can be essential to it. Instead of contingently related cause and effect, we have power and its manifestation, which remain distinct existences but with a necessary connection between. (kl 5971)

The language of causal powers allows us to incorporate a number of typical causal assertions in the social sciences: "Organizations of type X produce lower rates of industrial accidents," "paramilitary organizations promote fascist mobilization," "tenure systems in research universities promote higher levels of faculty research productivity." In each case we are asserting that a certain kind of social organization possesses, in light of the specifics of its rules and functioning, a disposition to stimulate certain kinds of participant behavior and certain kinds of aggregate outcomes. This is to attribute a specific causal power to species of organizations and institutions.

Stuart Glennan's "Mechanisms" is also highly relevant to causation in the social realm. Here is how Glennan puts the mechanisms theory (quoting his own earlier formulations):

Glennan ... characterizes mechanisms in this way: 'A mechanism underlying a behavior is a complex system which produces that behavior by the interaction of a number of parts according to direct causal laws (Glennan 1996: 52). Glennan then suggests that two events are causally related when and only when they are connected by an intervening mechanism. (kl 7069)

This definition works pretty well with typical examples of social mechanisms, with one important exception -- the reference to "direct causal laws". When we say that Organization X works to minimize accidents, the sub-transactions that are involved in the workings of the overall process are not typically "direct causal laws," but rather the intelligible results of individual actors performing their actions within the rules, incentives, and sanctions of the organization. We can tell a mechanism story along these lines: "Organization X embodies a set of protocols of operation, a training regime, a supervisory regime, and and enforcement regime. The protocols have the result that, when followed consistently, accidents are rare. Employees are 'programmed' to perform their tasks according to this set of protocols. Supervisors are trained to observe and measure employee performance against the protocols. Enforcement provides sanctions and incentives for bad and good performance." The complex mechanism of the organization works to implement and maintain the smooth functioning of the guiding protocols. So the organization embodies just the kind of complex system that Glennan describes as a mechanism.

So the Handbook is a good resource for all of us who are interested in working through a more satisfactory account of what it means to look at social phenomena as embodying causal relations in ways that support explanations.

(The photo of ice forming on glass included above is a metaphorical reference to social causation. Intricate patterns have emerged from a causal process; but it is a process that reflects a high degree of contingency and path-dependency across the expanse of the scene. And there is no overall order to the multiple patterns that emerge; each location is independent of other locations, and there is no answer to questions like this: "Why is Structure A located in the particular position and orientation that it is found to be?" Patterns coalesce and they do so as a result of locally operative causal processes, but there is no overall guiding hand or teleology to the process. The greatest disanalogy I can see here is the fact that the ice-formation process is much simpler than typical social-causal systems. Instead of a single causal mechanism at work in the ice case, there are dozens of overlapping and interactive causal mechanisms at work in most social processes.)

Macro causes of European fascism

Michael Mann's book Fascists makes use of causal claims at a range of levels, from the macro to the micro, to explain the emergence of European fascism.  Here is a passage that highlights four macro-level causes of fascism:

The interwar period in Europe was the setting that threw up most of the self-avowed fascists and saw them at their high tide. My definition is intended firstly as “European-epochal,” to use Eatwell’s (2001) term (cf. Kallis 2000: 96), applying primarily to that period and place – though perhaps with some resonance elsewhere. The period and the continent contained four major crises: the consequences of a devastating “world,” but in fact largely European, war between mass citizen armies, severe class conflict exacerbated by the Great Depression, a political crisis arising from an attempted rapid transition by many countries toward a democratic nation-state, and a cultural sense of civilizational contradiction and decay. Fascism itself recognized the importance of all four sources of social power by explicitly claiming to offer solutions to all four crises. And all four played a more specific role in weakening the capacity of elites to continue ruling in old ways. (23)

So what are the causal ideas expressed here?

The factors Mann singles out here are decidedly macro-level:

• war
• class conflict and economic depression
• rapid transition to democratic nation-states
• cultural impressions of decay

These are high-level social conditions involving military power, economic power, political power, and cultural realities. Perhaps not surprisingly, these factors correspond to the main legs of Mann's own theory of social power: "My earlier work identified four primary 'sources of social power' in human societies: ideological, economic, military, and political" (5).

So the causal factors identified here are clearly at the macro level.  The outcome Mann identifies is equally macro-level: the advent of fascist movements and governments in a handful of major European states.  So the basic claim here is a macro-macro causal claim.

The causal claims expressed in the paragraph can be summarized in this way:

• Factors F1, F2, F3, F4 each played a causal role in the rise of fascism
• Factors F1, F2, F3, F4 each weakened (caused) the capacity of elites to continue to rule

What is the meaning of the idea that "F1 played a causal role in the rise of fascism"? Most simply, it is the notion that the factor occupies a position in the full causal diagram or causal narrative of the rise of fascism, beginning at some point in time.  The action of hops in the process of brewing beer plays a causal role: many events and processes must occur in a timed sequence, but the activity of the hops is one necessary part of the overall process.

And how would an investigator piece together the causal narrative of a complex happening?  It would appear that the method of "process tracing" is the most direct way of piecing together a causal narrative.  This requires going through one or more empirical cases and probing the events that occurred to attempt to assess whether and how they played a causal role in the production of the outcome. This is exactly the form that Mann's investigation of the various fascisms of Europe takes; he examines the histories and tries to discern the causal sequences that are contained in them. (George Alexander and Andrew Bennett consider some of the challenges of this methodology in Case Studies and Theory Development in the Social Sciences.)

To say that a condition is a cause of a given outcome expresses as well the idea that the condition is either necessary or sufficient for the outcome; the presence or absence of the condition makes a difference for the occurrence of the outcome. The appearance of the cuckoo is neither necessary nor sufficient for the chiming of the clock; so the cuckoo is not a cause of the chiming. It would appear, then, that Mann is also committed to claims like this:

• If war and depression had not occurred then fascism would not have prevailed in Italy 
• If Spain's democracy had been more solid and well established, then fascism would not have prevailed in Spain

Other causal ideas are suggested by the paragraph, even if not explicit:

• War has the causal power to stimulate powerful social movements in combatant countries.
• Widespread economic depression has the causal power to stimulate class antagonism.
• Ideologies have the causal power to stimulate mobilization of adherents.
• Ideologies of cultural decay have the power to weaken the capacity of elites to govern.

How do these ideas about causal powers flesh out in detail?  How does "war" possess a causal power? War encompasses a complex set of circumstances and interlocking organizations: mobilization and demobilization of mass armies, disruption of civilian production, massive damage to people and property, unusual stresses on governments, etc. And each of these circumstances in turn has consequences which ultimately influence the circumstances in which the mass home population finds itself.  Those home circumstances in turn play into the factors that are known to stimulate and amplify social movements -- popular grievances about government, economic deprivation, a general environment of uncertainty, and the availability of entrepreneurial leaders and organizations prepared to take advantage of these conditions. So war has a causal power that is embodied by the social, economic, demographic, and political circumstances that accompany it; and that power is expressed through influence on the home population.

One way of encapsulating this kind of story about the causal powers of a structural circumstance is to say that the circumstance conditions and motivates actions by many individuals in ways that lead to a certain class of outcomes.  So the causal power story is also a Coleman's Boat kind of story; it is a specification of the microfoundations of the causal power in question.  However, once we have satisfied ourselves about the microfoundations, we are not compelled to retrace our steps through the individual level in order to move the argument from Italy to Spain. We can rely on the idea that war has a given set of causal powers on macro outcomes in the next case in which we observe war and disorder.

Causal realism and historical explanation

Are there plausible intuitions about the ways the world works that stand as credible alternatives to Hempel's covering law model? There are. A particularly strong alternative links explanation to causation, and goes on to understand causation in terms of the real causal powers of various entities and structures. Rom Harre's work explored this approach earliest (Madden and Harre, Causal Powers: Theory of Natural Necessity), and Roy Bhaskar's theories of critical realism push these intuitions further (Critical Realism: Essential Readings (Critical Realism: Interventions)). Bhaskar and Archer's volume Critical Realism: Essential Readings (Critical Realism: Interventions) (Bhaskar, Archer, Collier, Lawson, and Norrie, eds.) is a good exposure to current controversies in this tradition. Paul Lewis's "Realism, Causality, and the Problem of Social Structure" (link) is worth reading as well.

Here the idea is that causation is not to be understood along Humean lines, as no more than constant conjunction. (This is where the insistence on general laws originates.) Instead, the idea of a causal power is taken as a starting point. Things have the capacity to bring about changes of specific circumstances, in virtue of their inner constitution (or what Harre is content to call their essences). (I would put Nancy Cartwright's ideas about causation and general laws in the same general vicinity (How the Laws of Physics Lie, Nature's Capacities and Their Measurements), though she is not a critical realist. But her critique of laws and her preference for capacities is similar.)

This doesn't mean that there is a bright line between causal powers and regularities. If a certain thing X has the power to bring about Y, then it is true that there is some generalization available along the lines of "whenever X, Y occurs." The point here is about ontological primacy: is it the power or the law that is more fundamental? And Harre, Bhaskar, and Cartwright all agree that it is the power that is basic and the thing's powers are dependent upon its real constitution.

This set of realist intuitions about causation comports very well with the theory of causal mechanisms. According to this approach, when we ask for an explanation of something, we are asking questions along these lines: what are the real embodied mechanisms that bring about a given outcome? And what is the underlying substrate that gives these mechanisms their causal force?

When causal realism is brought to the social and historical sciences, it brings the idea that there are structures, entities, and forces in the social world that really exist and that supervene upon a substrate of activity that give substance to their causal powers. In the case of the social world, that substrate is the socially constituted, socially situated actor, or what I call the premise of methodological localism.

One implication of this ontology is directional for setting a program of inquiry. Instead of looking for general laws of a given domain, the researcher is encouraged to discover the particular causal properties and powers of specific kinds of things.

This emphasis on the particular and the local is particularly well suited to the challenges of historical and social research. Nancy Cartwright doubts the validity of searching for even exact laws of physics. And this doubt is all the more reasonable in the case of social phenomena. It is pointless to look for general laws of bureaucracy, the military, or colonialism. What is more promising, however, is to examine particular configurations of institutions and settings, and to attempt to determine their causal powers in the setting of a group of social actors.

Suppose we are interested in France's collapse in the Franco-Prussian War (link). We might expend significant research work on discerning the organizational and command structure of the French Army in the 1850s and 1860s. We might look in detail at Napoleon III's state apparatus, including its international relations bureau. And we might gather information on the structure, capacity, and organization of the French rail system. Then we might offer an explanation of a numer of events that occurred in 1870 as the result of the causal properties of those historically embodied organizations and institutions. The real performance properties of the rail system under a range of initial conditions can be worked out. The conditions presented by the rapid mobilization required by suddenly looming war can be investigated. And the logistical collapse that ensued can be explained as the result of the specific causal properties of that complex system. And here is an important point: the Italian rail system at the time had some similarities and some differences. So it is a matter of empirical and theoretical investigation to arrive at an account of the causal properties of that system. We cannot simply infer from the French case to the Italian case, and of course we can't hope to find a general law of rail systems.

The point here is a fundamental one. The covering law model depends on a metaphysics that gives primacy to laws of nature. The framework of critical realism and its cousins depends on a view of the world as consisting of things and processes with real causal powers. This intellectual framework is applicable to the social world as well as to the natural world. And it provides a strong intellectual basis for postulating and investigating social causal mechanisms. Any conception of causal powers requires that we have an idea of the nature of the substrate of causation in various areas. And the social metaphysics of actor-centered sociology provide a strong candidate for such a framework in the case of social causation.

Are mechanisms complex?

Source: D. Little, "Causal explanation in the social sciences" (link)

How can we distinguish between causal mechanisms and extended causal processes? Is the difference merely a pragmatic one, or is there some reason to expect that mechanisms should be compact and unitary in their workings? Is the children's story leading from the "want of the nail" to the loss of the kingdom a description of an extended mechanism or a contingent causal process?

My preferred definition of a social causal mechanism runs along these lines (“Causal Mechanisms in the Social Realm” (link)):

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. 

This captures the core idea presented in the Machamer-Darden-Craver (MDC) definition of a causal mechanism (link):

Mechanisms are entities and activities organized such that they are productive of regular changes from start or set-up to finish or termination conditions. (3)

There is also an ontological side of the concept of a mechanism -- the idea that there is a substrate that makes the mechanism work. By referring to a nexus between I and O as a "mechanism" we presume that there is some underlying ontology that makes the observed regularity a "necessary" one: given how the world works, the input I brings about events that lead to output O. In evolutionary biology it is the specifics of an ecology conjoined with natural selection. In the social world it is the empirical situation of the actor and the social and natural environment in which he/she acts.

So mechanisms reflect regularities of input and output. In this respect they correspond to pocket-sized social regularities: observed and sometimes theoretically grounded conveyances from one set of circumstances to another set of circumstances.  Take free riding as a mechanism arising within circumstances of collective action:

When a group of individuals confront a potential gain in public goods that can be attained only through effective and non-enforcible collective action, enough individuals will choose to be free riders to ensure the good is not achieved at the level desired by all members of the group.

This states a regularity (conditioned by ceteris paribus clauses): groups of independent individuals are commonly incapable of effective collective action. And it is grounded in a theory of the actor; rational individuals who pay attention to private costs and benefits but not public costs and benefits can be predicted to engage in free riding.

Now consider the mechanism described in social psychology as "stereotype threat" (link):

When subjects are exposed to signs of negative stereotypes of their group with respect to a given kind of performance, the average performance of the group declines.

This is a mechanism that can be identified in a number of different settings, both observational and experimental; and it can be combined with other mechanisms to bring about complex results. The substrate here is a set of hypothetical cognitive structures through which individuals process tasks and influence each other. 

Now consider an instance of concatenation. Suppose we are interested in military mistakes -- weighty decisions that look in hindsight to be surprisingly poor given the facts available to the decision makers at the time. Our theory of the case may involve three separate mechanisms that interfere with good reasoning: stereotype threat, inordinate hierarchicalism, and the effects of agenda setting. These are independent social cognitive mechanisms that impair group decision making. And our theory of the case may attempt to document the workings of each on the eventual outcome and the ways they aggregated to the observed decision. 

Are mechanisms thought to be simple, or can we consider composite mechanisms -- mechanisms composed of two or more simpler mechanisms? Our definition above required that a mechanism should link I to O with a sufficiently high probability to count as "likely". This puts a practical limit on the degree to which simple mechanisms can be composed into composite mechanisms. Take the sequential case: iMj (prob=.90) and jNk (prob=.90). Then let V be the sequential composite mechanism "M then N". Then we have iVk (prob=.81). The probability of the final endstate given the initial starting condition drops with each additional mechanism that we insert into the composite mechanism.  So eventually concatenation will bring the probability of an antecedent leading to a consequence below the threshold of likelihood required by the definition of a mechanism. 

McAdam, Tarrow and Tilly refer to a concatenation of mechanisms in a concrete instance as a process, not a higher-level mechanism.  The reason for this, it would seem, is that processes are highly contingent in their workings precisely because they incorporate multiple mechanisms in series and parallel, all of whose causal properties are probabilistic.  So there is no reason to expect that processes describe reliable associations between beginnings and endings.

So this implies that mechanisms should be conceived at a fairly low level of compositionality: to preserve the likelihood of association between antecedent and consequent, we need to identify fairly proximate mechanisms with predictable effects.  This doesn't mean that a mechanism has little or no internal structure; rather, it implies that the internal structure of a mechanism fits together in such a way as to bring about a strong correlation between cause and effect.  The mechanism of stereotype threat mentioned above presumably corresponds to a complex set of functionings within the human cognitive system. The net effect, however, is a strong correlation between cause (expressing a stereotype about performance to an individual) and effect (suppressing the level of performance of the individual).

Recent thinking about scientific explanation

What do we want from a scientific explanation?  Is there a single answer to this question, or is the field of explanation fundamentally heterogeneous, perhaps by discipline or by research community? Do biologists explain outcomes differently from physicists or sociologists? Is a good explanation within the Anglo-American traditions of science also a good explanation in the German or Chinese research communities? Is the idea of a scientific explanation paradigm-dependent?

For several decades in the twentieth century there was a dominant answer to this question, that was an outgrowth of the tradition of logical positivism and examples from the natural sciences. This theory of explanation focused on the idea of subsumption of an event or regularity under a higher-level set of laws. The deductive-nomological theory of explanation specified that an outcome is explained when we have produced a deductively valid argument with premises that include at least one general law and that lead to a description of the event as conclusion. Carl Hempel was the most prominent advocate for this theory (Aspects of Scientific Explanation), but it was widely accepted throughout the philosophy of science in the 1950s and 1960s.  The "covering law" model was a core dogma for the philosophy of science for several decades.

The D-N theory was subject to many kinds of criticisms, including the obvious point that much explanation involves phenomena that are probabilistic rather than deterministic.  Hempel introduced the inductive version of the D-N model to cover probabilistic-statistical explanation, along these lines. An argument provides a scientific explanation of E if it provides at least one probabilistic law and a set of background conditions such that, given the law and conditions, E is highly probable.  This model was described as the "Inductive-Statistical" model (I-S model).  Wesley Salmon's Scientific Explanation and the Causal Structure of the World falls within this tradition but offers important refinements, including his formal definition of causal relevance.

In each case the motivation for the theory of explanation is a plausible one: we explain an event when we show how it was necessary [or highly probable] in the circumstances, given existing conditions and relevant laws of nature. On the logical positivist approach, an explanation is an answer to a "why necessary" question: why did this event occur? In this conception of explanation the idea of necessity or probability is replaced with the idea of deductive or inductive derivability -- a syntactic relationship among sets of sentences.

A different approach to explanation turns to the idea of causation.  We provide an explanation of an event or pattern when we succeed in identifying the causal conditions and events that brought it about.  This approach can be tied to the D-N approach, if we believe that all causal relations are the manifestation of strict or probabilistic causal regularities.  But not all D-N explanations are causal, and not all causal explanations invoke regularities.  Derivability is no longer the criterion of explanatory success, and explanation is no longer primarily a syntactic relation between sets of sentences.  Instead, substantive theories of causal powers and properties are the foundation of scientific explanation.  A leading exponent of this view is Rom Harré in Harré and Madden, Causal Powers: Theory of Natural Necessity. Nancy Cartwright's Nature's Capacities and Their Measurements is also an important contribution to this view.  And J. L. Mackie's The Cement of the Universe: A Study of Causation is an important contribution as well.  The causal approach retains the idea that explanation involves showing why an event is necessary or probable, but it turns from derivability from statements of laws of nature, to theories of causal powers and properties.

The causal mechanisms approach to explanation continues the insight that explanations involve demonstrating why an event occurred; but this approach moves even farther away from the idea of a causal law, replacing it with the idea of a discrete causal mechanism.  On this approach, we explain an event when we identify a series of causal interactions that lead from some antecedent condition to the outcome of interest.  Hedstrom and Swedborg's Social Mechanisms: An Analytical Approach to Social Theory presents aspects of this theory of explanation in application to the social sciences.  One benefit of the social mechanisms approach is that it also provides a basis for answering "how possible" questions: if our puzzlement is that an outcome has occurred that seems inherently unlikely, we can provide an account of a set of causal mechanisms that transpired to bring it about.

The chief line of dispute in the traditions mentioned so far is between the "general laws" camp and the "causal powers" camp.  Both are committed to the idea that explanation involves showing how an outcome fits into the ways the world works; but the general laws approach presumes that law-like regularities are fundamental, whereas the causal approach presumes that causal powers and mechanisms are fundamental.

So what has developed in the theory of explanation in the past twenty years? Quite a bit. A recent collection of essays coming largely from the Scandinavian tradition of the philosophy of science is quite helpful in orienting readers to recent developments. This is Johannes Persson and Petri Ylikoski's 2007  Rethinking Explanation. Quite a number of the contributions are worth reading carefully.  But Jan Faye's "Pragmatic-Rhetorical Theory of Explanation" is a good place to start.  Faye distinguishes among three basic approaches to the theory of explanation: formal-logical, ontological, and pragmatic.  The formal-logical approach is essentially the H-D and I-S approaches described above.  The ontological approach is the causal-powers approach described above.  The pragmatic approach is in a sense the most important recent contribution to the theory of explanation, and represents a significant re-focusing of the debates in post-empiricist philosophy of science. Here is how Faye describes the pragmatic approach to explanation-theory:

The pragmatic view sees scientific explanations to be basically similar to explanations in everyday life. It regards every explanation as an appropriate answer to an explanation-seeking question, emphasising that the context of the discourse, including the explainer’s interest and background knowledge, determines the appropriate answer. (44)

And why should we consider a pragmatic approach?  Faye offers eight reasons:

First, we have to recognise that even within the natural sciences there exist many different types of accounts, which scientists regard as explanatory. (46)

Second, if one is looking for a prescriptive treatment of explanation, I see no reason why the social sciences and the humanities should be excluded from such a prescription. If they are included, the prescriptive account must include intentional and interpretive explanations, i.e., accounts providing information about either motives or meanings. (47)

Third, the meaning of a why-question alone does not determine whether the answer is relevant or not. (47)

Fourth, John Searle has correctly argued that the meaning of every indicative sentence is context-dependent. He does not deny that many sentences have literal meaning, which is traditionally seen as the semantic content a sentence has independently of any context. (49)

Fifth, many explanations take the form of stories. Arthur Danto has argued that what we want to explain is always a change of some sort. When a change occurs, we have one situation before and another situation after, and the explanation is what connects these two situations. This is the story. (50)

Sixth, a change always takes place in a complex causal field of circumstances each of which is necessary for its occurrence. Writers like P.W. Bridgman, Norwood Russell Hanson, John Mackie, and Bas van Fraassen have all correctly argued that events are enmeshed in a causal network and that it is the salient factors mentioned in an explanation that constitute the causes of that events. (50)

Seventh, the level of explanation depends also on our interest of communication. In science an appropriate nomic or causal account can be given on the basis of different explanatory levels, and which of these levels one selects as informative depends very much on the rhetorical purposes. (51)

Eight, scientific theories are empirically underdetermined by data. It is always possible to develop competing theories that explain things differently and, therefore, it is impossible to set up a crucial experiment that shows which of these theories that yields the correct account of the data available. (52)

Faye then goes on to analyze scientific explanation as a speech act. We need to understand the presuppositions and purposes that the explainer and the listener have, before we can say much about how the explanation works.

Petri Ylikoski's contribution to the volume, "The Idea of Contrastive Explanandum," picks up on one particular but pervasively important feature of the rhetorical situation of explanation, the idea of contrast.  When we ask for an explanation of an outcome, often we are not asking simply why it occurred, but rather why it occurred instead of something else.  And the contrastive condition is crucial.  If we ask "why did the Prussian army win the Franco-Prussian War?", the answer we give will be very different depending on whether we understand the question as:

"Why did the Prussian army [rather than the French army] win the Franco-Prussian War?"

or:

"Why did the Prussian army win [rather than fighting to stalemate] the Franco-Prussian War?"

So scientific explanation is context-dependent in at least this important respect: we need to understand what the question-asker has in mind before we can provide an adequate explanation from his/her point of view. As Henrik Hallsten puts it in his contribution, "What to Ask of an Explanation-Theory",

To summarize: Any explanation-theory must [do] justice to the distinction between objective explanatory relevance and context dependent explanatory relevance or provide good arguments as to why this distinction should not be upheld. (16)

So perhaps the most important recent developments in the theory of scientific explanation fall in a few categories.  First, there has been substantial work on refining the idea of causal explanation (link).  Second, philosophers have reinforced the idea that explanation has pragmatic and rhetorical aspects that cannot be put aside in favor of syntactic and substantive features of explanation. And third, there is more recognition and acceptance of the idea that explanatory models and standards may reasonably differ across disciplines and research areas.  In particular, the social and historical sciences are entitled to offer explanatory frameworks that are well adapted to the particular kinds of why and how questions that are posed in these fields.   In each case the philosophy of science has made a very great deal of progress since the state of the debates about explanation that transpired in the 1960s.

Current issues in causation research

This week's conference on Causality and Explanation in the Sciences in Ghent was an unusually good academic meeting (link). Participants gathered from all over Europe, as well as a few from North America, Australia, and South Africa, to debate the logic and substance of causal interpretations of the world. Among other things, it provided all participants with a very good sense of the ideas about causation that are generating the most discussion today.

A general perception that emerges from the gestalt of papers at the conference is that there are three large focus areas in current research on scientific causation. First, there is interest in specifying what causal assertions and concepts mean in scientific explanations. What are the logical, conceptual, and pragmatic issues associated with causal assertions and explanations?

Second, there is a large body of work focusing on the methods we can use to support causal inference in the sciences. Every field of science produces volumes of data about variables and events over time. What methods exist to permit inferences about causal relationships among the observed variables and entities? This includes causal modeling statistical methods, but also comparative methods deriving from Mill's methods of difference and similarity.

Third, there is a group of philosophers and scientists who are primarily interested in the ontology of causation in various parts of the sciences. How do various factors exercise causal powers in ecology, the social sciences, or complex systems? Researchers in these areas need provisional answers to questions raised by the first two groups, but their focus is on substantive causal processes rather than the logic of causal statements.

It is useful to inventory half a dozen approaches that were repeatedly cited. This survey is impressionistic but gives an idea of the current landscape.

The mechanisms approach. The idea that we can explicate causation through the idea of a mechanism has been rising in importance over the past twenty years. The idea here is that the fundamental causal concept is that of a mechanism through which X brings about or produces Y. This is argued to be key to causation from single-case studies to large statistical studies suggesting a causal relationship between two or more variables. Peter Hedstrom and other exponents of analytical sociology are recent voices for this approach for the social sciences, though expositions of this approach don't usually go into the level of detail expected by philosophers like Woodward and Cartwright. An important paper by Peter Machamer, Lindley Darden and Carl Craver, "Thinking about Mechanisms", sets the terms of current technical discussions; their view is referred to as the MDC theory. A common concern is that the approach hasn't been as clear as it should be about what precisely a mechanism is. James Mahoney made this criticism in 2001 in "Beyond Correlational Analysis" reviewing Charles Ragin, Fuzzy-Set Social Science and Peter Hedstrom and Richard Swedberg, Social Mechanisms: An Analytical Approach to Social Theory (link), and we still need a more generally recognized specification of the idea. (See an earlier post on this approach; link.)

The manipulability account. Jim Woodward is perhaps the leading exponent of the manipulability (or interventionist) account. He develops his views in detail in his recent book, Making Things Happen: A Theory of Causal Explanation. The view is an intuitively plausible one: causal claims have to do with judgments about how the world would be if we altered certain circumstances. If we observe that the concentration of sulphuric acid is increasing in the atmosphere, we might consider the increasing volume of H2SO4 released by coal power plants from 1960 to 1990. And we might speculate that there is a causal connection between these facts. A counterfactual causal statement holds that: If X (increasing emissions) had not occurred, then Y (increasing acid rain) would not have occurred. The manipulability theory adds this point: if we could remove X from the sequence, then we would alter the value of Y. And this in turn makes good sense of the ways in which we design controlled experiments.

Difference-making. Another strand of thinking about causation focuses on the explanations we are looking for when we ask about the cause of some outcome. Here philosophers note that there are vastly many conditions that are causally necessary for an event but do not count as being explanatory. Lee Harvey Oswald was alive when he fired his rifle in Dallas; but this doesn't play an explanatory role in the assassination of Kennedy. Crudely speaking, we want to know which causal factors were salient; which factors made a difference in the outcome. Michael Strevens provides a detailed and innovative explication of this set of intuitions in his recent book Depth: An Account of Scientific Explanation, where he introduces his theory of "Kairetic" explanation.

Contrastive analysis as a theory of explanation. When we seek an explanation of something, we generally have something specific in mind: why X rather than X'? And an explanation that keys off the wrong contrast will fail, even though its premises are correct. Bas van Fraassen (1980), The Scientific Image, is often cited in this context. A conference participant, Petri Ylikoski, develops a contrastive counterfactual theory in his dissertation (link). This body of work seeks to clarify pragmatic issues concerning explanation, including understanding and explanatory relevance. If we ask for an explanation for why X occurred, we are usually presupposing a question like this:

Why did X occur [rather than Y]?

• Why is John carrying his umbrella [rather than not]?
• Why is John carrying his umbrella [rather than his raincoat]?
• Why is John carrying his umbrella [rather than his assistant Harry]?

These all demand different answers:

• Because he expects rain;
• Because it is too warm for a raincoat;
• Because Harry is carrying three heavy suitcases.

Here is a much-cited review article by Nancy Cartwright on van Fraasen's work (link), and here is a discussion of contrastive explanation by Jonathan Schaffer (link).

Causal modeling theory. This topic refers to the large body of statistical theory devoted to identifying potential causal relationships among observable variables in a large data set. Hubert Blalock is a founder of this approach (Causal Inferences in Nonexperimental Research; 1964) with his statistical models for causal path analysis. (Here is a short account of the history of path analysis in genetics.) Judea Pearl has contributed a great deal to the method of structural equation modeling (SEM) in Causality: Models, Reasoning and Inference and elsewhere. Here is a handbook article in which he explains the method and its causal relevance (link). Pearl maintains a research blog on causality here. Granger causality is a specific technique for assessing causal relationships within time series data: X Granger-causes Y if variations in X and Y together do a better job of predicting Y than variations in Y by itself.

Prior foundations of philosophical theories of causation. Two older discussions of causality also received some notice in these papers: J. L. Mackie on INUS conditions and causal fields (The Cement of the Universe: A Study of Causation) and Wesley Salmon on the causal structure of the world (Scientific Explanation and the Causal Structure of the World).

Nancy Cartwright's "Causation: One Word, Many Things" provides a very good contemporary review of the varieties of approaches that are currently being taken to the idea of causation (link).

Much of the intellectual vitality of this group of philosophers is captured in the major work recently edited by Phyllis McKay Illari, Federica Russo, and John Williamson, Causality in the Sciences. The book contains a very wide range of disciplines and approaches in its treatment of the topic.

Woodward on mechanisms

Jim Woodward has extended a lot of his philosophical effort towards the task of understanding causation in the sciences (Making Things Happen: A Theory of Causal Explanation). Woodward is a primary exponent of the "manipulationist" theory of causation. He brings a counterfactual orientation to the problem of defining causal relations. If we assert that X caused Y, there is an implication that, if X had not occurred, Y would not have occurred. This implication isn't universally valid, since some events or outcomes are causally overdetermined. (Both X and X' may be a sufficient cause for Y -- in which case removing X still allows for Y through the X' pathway.) Notwithstanding this problem, the counterfactual nature of causal assertions is widely recognized. And this implies the association between causation and intervention or manipulation: if X causes Y, then we should be able to influence the occurrence of Y by manipulating X. This fact in turn underlies the logic of experimental design.

Woodward's treatment of causation deserves fuller treatment than I'll give it here. In this post I will focus on his application of these ideas to the notion of a causal mechanism. He lays this treatment out in a short but influential article, "What is a Mechanism? A Counterfactual Account" (link).

Here is the core idea. He focuses on the Machamer-Darden-Craver (MDC) definition of a causal mechanism (link):

Mechanisms are entities and activities organized such that they are productive of regular changes from start or set-up to finish or termination conditions. (3)

Woodward's contribution is to give greater clarity to the idea of regularity or law by adding the idea of a relationship that is "invariant under intervention". This idea models the notion of experimental testing of a causal hypothesis. We are interested in "X causes Y". We look for interventions that change the state of Y. If we find that the only interventions that change Y, do so through their ability to change X, then the X-Y relation is said to be invariant under intervention, and X is said to cause Y. Here is how he expresses the idea in the article:

I understand this in terms of the notion of invariance under interventions. Suppose that X and Y are variables that can take at least two values. The notion of an intervention attempts to capture, in non-anthropomorphic language that makes no reference to notions like human agency, the conditions that would need to be met in an ideal experimental manipulation of X performed for the purpose of determining whether X causes Y. The intuitive idea is that an intervention on X with respect to Y is a change in the value of X that changes Y, if at all, only via a route that goes through X and not in some other way. This requires, among other things, that the intervention not be correlated with other causes of Y except for those causes of Y (if any) that are causally between X and Y and that the intervention not affect Y independently of X. Thus if A is a common cause of B and S as in the example above, manipulating B by manipulating A will not count as an intervention on B with respect to S since in this case the manipulation affects S via a route (the route that connects A to S ) that does not go through B. (369-70)

Here is how he applies this idea to causal mechanisms. A mechanism consists of separate components that have intervention-invariant relations to separate sets of outcomes. These components are modular: they exercise their influence independently. And, like keys on an accordion, they can be separately activated with discrete results.

So far I have been arguing that components of mechanisms should behave in accord with regularities that are invariant under interventions and support counterfactuals about what would happen in hypothetical experiments. (374)

Here is the proposal all of this leads up to:

(MECH) a necessary condition for a representation to be an acceptable model of a mechanism is that the representation (i) describe an organized or structured set of parts or components, where (ii) the behavior of each component is described by a generalization that is invariant under interventions, and where (iii) the generalizations governing each component are also independently changeable, and where (iv) the representation allows us to see how, in virtue of (i), (ii) and (iii), the overall output of the mechanism will vary under manipulation of the input to each compo- nent and changes in the components themselves. (375)

Woodward illustrates his theory of mechanisms with simple physical and biological examples. How does this theory work when we consider social mechanisms?

What seems most evident is that social mechanisms are not commonly as complex as Woodward's examples would suggest. The sorts of mechanisms that crop up in sociology seem largely to be "simple" mechanisms: they don't consist of multiple independent components leading to an outcome.

Here is the way that McAdam, Tarrow and Tilly (MTT) characterize mechanisms and processes 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.
• Processes are regular sequences of such mechanisms that produce similar (generally more complex and contingent) transformations of those elements. (24)

These definitions imply that processes are compound, whereas typical mechanisms are simple.

Here are examples that MTT offer of mechanisms:

• resource depletion or enhancement affects people's capacity to engage in contentious politics (25)
• commitment is a widely recurrent individual mechanism in which persons who individually would prefer not to take the risks of collective action find themselves unable to withdraw without hurting others whose solidarity they value (26)
• Brokerage ... 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 (26)
• Identity shift ... alteration during contentious claim making of public answers to the question: "Who are you?" (27)

In each case we seem to have a simple relationship between one social or environmental fact and a typical outcome -- not a complex concatenation of "cogs and wheels" of social interaction.

So when we consider typical examples of social mechanisms -- free-riding (Olson), escalation (McAdam-Tarrow-Tilly), identity competition (Horowitz) -- we commonly find that they are all basically one-step mechanisms. So the assumption that a mechanism consists of modular components doesn't fit the social sciences well. There are complex social processes, to be sure, but it seems best to understand these as concatenations of distinct mechanisms rather than as a single complex mechanism. (Why? Because they are all too often unrepeatable.)

This doesn't mean that we can't understand social mechanisms along the lines Woodward suggests, if we are content to acknowledge that it is hard to find complex social mechanisms. But in order for even this to be the case, we would have to confirm that these simple mechanisms produce intervention-invariant regularities.

This requirement runs up against a different problem, however. The regularities that correspond to typical social mechanisms are soft regularities, not hard-and-fast laws. Social causation is probabilistic, not deterministic. The regularities corresponding to social causes derive from features of human agency and behavior, and they are deeply exception-laden. The free-rider mechanism tends to give rise to under-investment in the public good -- except when people self-organize, semi-coercive organizations appear, or altruistic religious attitudes take hold. Social mechanisms are productive, in the sense that they "bring about" the associated outcomes. But they are not invariant across all or most cases.

This implies that there are no intervention-invariant relations to be had in the social world. And therefore we need some other analytical foundation if we are to persist in thinking there are social causal mechanisms.

Woodward addresses something very much like this possibility in conjunction with psychological mechanisms. And he draws a prescriptive conclusion: if the "mechanisms" cited in psychology do not have these characteristics of modularity and invariance, then they aren't really mechanisms:

the standard boxological diagrams allegedly describing the operation of psychological mechanisms drawn by psychologists are rarely accompanied by convincing evidence that the parts corresponding to the boxes satisfy the modularity condition described above. If the argument of this paper is correct, this is a reason for being skeptical that these diagrams describe genuine mechanisms. (377)

It seems likely enough that he would reach a similar conclusion about the kinds of mechanisms offered by MTT.

(Here is an excellent review by Michael Strevens of Woodward, Making Things Happen.)