Sunday, February 16, 2020

Generativity and emergence


Social entities and structures have properties that exercise causal influence over all of us, and over the continuing development of the society in which we live. Schools, corporations, armies, terror networks, transport networks, markets, churches, and cities all fall in this range -- they are social compounds or entities that shape the behavior of the individuals who live and work within them, and they have substantial effects on the broader society as well.

So it is unsurprising that sociologists and ordinary observers alike refer to social structures, organizations, and practices as real components of the social world. Social entities have properties that make a difference, at the individual level and at the social and historical level. Individuals are influenced by the rules and practices of the organizations that employ them; and political movements are influenced by the competition that exists among various religious organizations. Putting the point simply, social entities have real causal properties that influence daily life and the course of history.

What is less clear in the social sciences, and in the areas of philosophy that take an interest in such things, is where those causal properties come from. We know from physics that the causal properties of metallic silver derive from the quantum-level properties of the atoms that make it up. Is something parallel to this true in the social realm as well? Do the causal properties of a corporation derive from the properties of the individual human beings who make it up? Are social properties reducible to individual-level facts?

John Stuart Mill was an early advocate for methodological individualism. In 1843 he wrote his System of Logic: Ratiocinative and Inductive, which contained his view of the relationships that exist between the social world and the world of individual thought and action:
All phenomena of society are phenomena of human nature, generated by the action of outward circumstances upon masses of human beings; and if, therefore, the phenomena of human thought, feeling, and action are subject to fixed laws, the phenomena of society can not but conform to fixed laws. (Book VI, chap. VI, sect. 2)
With this position he set the stage for much of the thinking in social science disciplines like economics and political science, with the philosophical theory of methodological individualism.

About sixty years later Emile Durkheim took the opposite view. He believed that social properties were autonomous with respect to the individuals that underlie them. In 1901 he wrote in the preface to the second edition of Rules of Sociological Method:
Whenever certain elements combine and thereby produce, by the fact of their combination, new phenomena, it is plain that these new phenomena reside not in the original elements but in the totality formed by their union. The living cell contains nothing but mineral particles, as society contains nothing but individuals. Yet it is patently impossible for the phenomena characteristic of life to reside in the atoms of hydrogen, oxygen, carbon, and nitrogen.... Let us apply this principle to sociology. If, as we may say, this synthesis constituting every society yields new phenomena, differing from those which take place in individual consciousness, we must, indeed, admit that these facts reside exclusively in the very society itself which produces them, and not in its parts, i.e., its members.... These new phenomena cannot be reduced to their elements. (preface to the 2nd edition)
These ideas provided the basis for what we can call "methodological holism".

So the issue between Mill and Durkheim is the question of whether the properties of the higher-level social entity can be derived from the properties of the individuals who make up that entity. Mill believed yes, and Durkheim believed no.

This debate persists to the current day, and the positions are both more developed, more nuanced, and more directly relevant to social-science research. Consider first what we might call "generativist social-science modeling". This approach holds that methodological individualism is obviously true, and the central task for the social sciences is to actually perform the reduction of social properties to the actions of individuals by providing computational models that reproduce the social property based on a model of the interacting individuals. These models are called "agent-based models" (ABM). Computational social scientist Joshua Epstein is a recognized leader in this field, and his book Growing Artificial Societies: Social Science From the Bottom Up provides developed examples of ABMs designed to explain well-known social phenomena from the disappearance of the Anasazi in the American Southwest to the occurrence of social unrest. Here is his summary statement of the approach:
To the generativist, explaining macroscopic social regularities, such as norms, spatial patterns, contagion dynamics, or institutions requires that one answer the following question: How could the autonomous local interactions of heterogeneous boundedly rational agents generate the given regularity?Accordingly, to explain macroscopic social patterns, we generate—or “grow”—them in agent models. 
Epstein's memorable aphorism summarizes the field -- "If you didn't grow it, you didn't explain its emergence." A very clear early example of this approach is an agent-based simulation of residential segregation provided by Thomas Schelling in "Dynamic Models of Segregation" (Journal of Mathematical Sociology, 1971; link). The model shows that simple assumptions about the neighborhood-composition preferences of individuals of two groups, combined with the fact that individuals can freely move to locations that satisfy their preferences, leads almost invariably to strongly segregated urban areas.

There is a surface plausibility to the generativist approach, but close inspection of many of these simulations lays bare some important deficiencies. In particular, a social simulation necessarily abstracts mercilessly from the complexities of both the social environment and the dynamics of individual action. It is difficult to represent the workings of higher-level social entities within an agent-based model -- for example, organizations and social practices. And ABMs are not well designed for the task of representing dynamic social features that other researchers on social action take to be fundamental -- for example, the quality of leadership, the content of political messages, or the high degree of path dependence that most real instances of political mobilization reflect.

So if methodological individualism is a poor guide to social research, what is the alternative? The strongest opposition to generativism and reductionism is the view that social properties are "emergent". This means that social ensembles sometimes possess properties that cannot be explained by or reduced to the properties and actions of the participants. For example, it is sometimes thought that a political movement (e.g. Egyptian activism in Tahrir Square in 2011) possessed characteristics that were different in kind from the properties of the individuals and activists who made it up.

There are a few research communities currently advocating for a strong concept of emergence. One is the field of critical realism, a philosophy of science developed by Roy Bhaskar in A Realist Theory of Science (1975) and The Possibility of Naturalism (1979). According to Bhaskar, we need to investigate the social world by looking for the real (though usually unobservable) mechanisms that give rise to social stability and change. Bhaskar is anti-reductionist, and he maintains that social entities have properties that are different in kind from the properties of individuals. In particular, he believes that the social mechanisms that generate the social world are themselves created by the autonomous causal powers of social entities and structures. So attempting to reduce a process of social change to the actions of the individuals who make it up is a useless exercise; these individuals are themselves influenced by the autonomous causal powers of larger social forces.

Another important current line of thought that defends the idea of emergence is the theory of assemblage, drawn from Gilles Deleuze but substantially developed by Manuel DeLanda in A New Philosophy of Society: Assemblage Theory and Social Complexity (2006) and Assemblage Theory (2016). This theory argues for a very different way of conceptualizing the social world. This approach proposes that we should understand complex social entities as a compound of heterogeneous and independent lesser entities, structures, and practices. Social entities do not have "essences". Instead, they are continent and heterogenous ensembles of parts that have been brought together in contingent ways. But crucially, DeLanda maintains that assemblages too have emergent properties that do not derive directly from the properties of the parts. A city has properties that cannot be explained in terms of the properties of its parts. So assemblage theory too is anti-reductionist. 

The claim of emergence too has a superficial appeal. It is clear, for one thing, that social entities have effects that are autonomous with respect to the particular individuals who compose them. And it is clear as well that there are social properties that have no counterpart at the individual level (for example, social cohesion). So there is a weak sense in which it is possible to accept a concept of emergence. However, that weak sense does not rule out either generativity or reduction in principle. It is possible to hold both generativity and weak emergence consistently. And the stronger sense -- that emergent properties are unrelated to and underivable from lower level properties -- seems flatly irrational. What could strongly emergent properties depend on, if not the individuals and social relations that make up these higher-level social entities?

For this reason it is reasonable for social scientists to question both generativity and strong emergence. We are better off avoiding the strong claims of both generativity and emergence, in favor of a more modest social theory. Instead, it is reasonable to advocate for the idea of the relative explanatory autonomy of social properties. This position comes down to a number of related ideas. Social properties are ultimately fixed by the actions and thoughts of socially constituted individuals. Social properties are stable enough to admit of direct investigation. Social properties are relatively autonomous with respect to the specific individuals who occupy positions within these structures. And there is no compulsion to perform reductions of social properties through ABMs or any other kind of derivation. (These are ideas that were first advocated in 1974 by Jerry Fodor in "Special sciences: Or: The disunity of science as a working hypothesis" (link).)

It is interesting to note that a new field of social science, complexity studies, has relevance to both ends of this dichotomy. Joshua Epstein himself is a complexity theorist, dedicated to discovering mathematical methods for understanding complex systems. Other complexity scientists like John Miller and Scott Page are open to the idea of weak emergence in Complex Adaptive Systems: An Introduction to Computational Models of Social Life. Here is how Miller and Page address the idea of emergence in CAS:
The usual notion put forth underlying emergence is that individual, localized behavior aggregates into global behavior that is, in some sense, disconnected from its origins. Such a disconnection implies that, within limits, the details of the local behavior do not matter to the aggregate outcome. (CAS, p. 44)
Herbert Simon is another key contributor to modern complexity studies. Simon believed that complex systems have properties that are irreducible to the properties of their components for pragmatic reasons, including especially computational intractability. It is therefore reasonable, in his estimation, to look at higher-level social properties as being emergent -- even though we believe in principle that these properties are ultimately determined by the properties of the components. Here is his treatment in the third edition of The Sciences of the Artificial - 3rd Edition (1996):
[This amounts to] reductionism in principle even though it is not easy (often not even computationally feasible) to infer rigorously the properties of the whole from knowledge of the properties of the parts. In this pragmatic way, we can build nearly independent theories for each successive level of complexity, but at the same time, build bridging theories that show how each higher level can be accounted for in terms of the elements and relations of the next level down. (172)
The debate over generativity and emergence may seem like an arcane issue that is of interest only to philosophers and the most theoretical of social scientists. But in fact, disputes like this one have real consequences for the conduct of an area of scientific research. Suppose we are interested in the sociology of hate-based social movements. If we begin with the framework of reductionism and generativism, we may be led to focus on the social psychology of adherents and the aggregative processes through which potential followers are recruited into a hate-based movement. If, on the other hand, we believe that social structures and practices have relatively autonomous causal properties, then we will be led to consider the empirical specifics of the workings of organizations like White Citizens Councils, legal structures like the laws that govern hate-based political expressions in Germany and France, and the ways that the Internet may influence the spread of hate-based values and activism. In each of these cases the empirical research is directed in important measure to the concrete workings of the higher-level social institutions that are hypothesized to influence the emergence and shape of hate-based movements. In other words, the sociological research that we conduct is guided in part by the assumptions we make about social ontology and the composition of the social world.

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