Here I want to highlight this concept by asking a few foundational questions. Fundamentally, what kind of concept is it? How does it function in social interpretation, description, or explanation? And how does it function as a component of empirical investigation?
The concept of moral economy was extensively developed by E. P. Thompson in The Making of the English Working Class (1961) and an important essay, "The Moral Economy of the English Crowd in the Eighteenth Century," originally published in Past and Present in 1971 and included in Customs in Common: Studies in Traditional Popular Culture. The concept derives from Thompson's treatment of bread riots in eighteenth century Britain. In MEWC Thompson writes:
In 18th-century Britain riotous actions assumed two different forms: that of more or less spontaneous popular direct action; and that of the deliberate use of the crowd as an instrument of pressure, by persons "above" or apart from he crowd. The first form has not received the attention which it merits. It rested upon more articulate popular sanctions and was validated by more sophisticated traditions than the word "riot" suggests. The most common example is the bread or food riot, repeated cases of which can be found in almost every town and county until the 1840s. This was rarely a mere uproar which culminated in the breaking open of barns or the looting of shops. It was legitimised by the assumptions of an older moral economy, which taught the immorality of any unfair method of forcing up the price of provisions by profiteering upon the necessities of the people. (MTWEC, 62-63)
After describing a number of bread riots in some detail, Thompson writes, "Actions on such a scale ... indicate an extraordinarily deep-rooted pattern of behaviour and belief .... These popular actions were legitimised by the old paternalist moral economy" (66). And he closes this interesting discussion with these words: "In considering only this one form of 'mob' action we have come upon unsuspected complexities, for behind every such form of popular direct action some legitimising notion of right is to be found" (68). And Thompson often describes these values as "traditional" or "paternalist" -- working in opposition to the values and ideas of an unfettered market; he contrasts "moral economy" with the modern "political economy" associated with liberalism and the ideology of the free market.
In "The Moral Economy of the Crowd" Thompson puts his theory this way:
It is possible to detect in almost ever eighteenth-century crowd action some legitimising notion. By the notion of legitimation I mean that the men and women in the crowd were informed by the belief that they were defending traditional rights or customs; and, in general, that they were supported by the wider consensus of the community. On occasion this popular consensus was endorsed by some measure of licence afforded by the authorities. More commonly, the consensus was so strong that it overrode motives of fear or deference. ("Moral Economy," CIC 188)
It is plain from these passages that Thompson believes that the "moral economy" is a real historical factor, consisting of the complex set of attitudes and norms of justice that are in play within this historically presented social group. As he puts the point late in the essay, "We have been examining a pattern of social protest which derives from a consensus as to the moral economy of the commonweal in times of dearth" (247).
So the logic of Thompson's ideas here seems fairly clear: there were instances of public disorder ("riots") surrounding the availability and price of food, and there is a hypothesized "notion of right" or justice that influenced and motivated participants. This conception of justice is a socially embodied historical factor, and it partially explains the behavior of the rural people who mobilized themselves to participate in the disturbances. He recapitulates his goal in the essay, "Moral Economy Reviewed" (also included in Customs in Common) in these terms: "My object of analysis was the mentalité, or, as I would prefer, the political culture, the expectations, traditions, and indeed, superstitions of the working population most frequently involved in actions in the market" (260). These shared values and norms play a key role in Thompson's reading of the political behavior of the individuals in these groups. So these hypotheses about the moral economy of the crowd serve both to help interpret the actions of a set of actors involved in food riots, and to explain the timing and nature of food riots. We might say, then, that the concept of "moral economy" contributes both to a hermeneutics of peasant behavior and a causal theory of peasant contention.
Now move forward two centuries. Another key use of the concept of moral economy occurs in treatments of modern peasant rebellions in Asia. Most influential is James Scott's important book, The Moral Economy of the Peasant: Rebellion and Subsistence in Southeast Asia. Scholars of the Chinese Revolution borrowed from Scott in offering a range of interpretations of peasant behavior in the context of CCP mobilization; for example, James Polachek ("The Moral Economy of the Kiangsi Soviet" (1928-34). Journal of Asian Studies 1983 XLII (4):805-830). And most recently, Kevin O'Brien has made use of the idea of a moral economy in his treatment of "righteous protest" in contemporary China (Rightful Resistance in Rural China). So scholars interested in the politics of Asian rural societies have found the moral economy concept to be a useful one. Scott puts his central perspective in these terms:
We can learn a great deal from rebels who were defeated nearly a half-century ago. If we understand the indignation and rage which prompted them to risk everything, we can grasp what I have chosen to call their moral economy: their notion of economic justice and their working definition of exploitation--their view of which claims on their product were tolerable and which intolerable. Insofar as their moral economy is representative of peasants elsewhere, and I believe I can show that it is, we may move toward a fuller appreciation of the normative roots of peasant politics. If we understand, further, how the central economic and political transformations of the colonial era served to systematically violate the peasantry's vision of social equity, we may realize how a class "of low classness" came to provide, far more often than the proletariat, the shock troops of rebellion and revolution. (MEP, 3-4)
Scott's book represents his effort to understand the dynamic material circumstances of peasant life in colonial Southeast Asia (Vietnam and Burma); to postulate some central normative assumptions of the "subsistence ethic" that he believes characterizes these peasant societies; and then to explain the variations in political behavior of peasants in these societies based on the moments of inconsistency between material conditions and aspects of the subsistence ethic. And he postulates that the political choices for action these peasant rebels make are powerfully influenced by the content of the subsistence ethic. Essentially, we are invited to conceive of the "agency" of the peasant as being a complicated affair, including prudential reasoning, moral assessment based on shared standards of justice, and perhaps other factors as well. So, most fundamentally, Scott's theory offers an account of the social psychology and agency of peasants.
There are several distinctive features of Scott's programme. One is his critique of narrow agent-centered theories of political motivation, including particularly rational choice theory. (Samuel Popkin's The Rational Peasant: The Political Economy of Rural Society in Vietnam is the prime example.) Against the idea that peasants are economically rational agents who decide about political participation based on a narrowly defined cost-benefit analysis, Scott argues for a more complex political psychology incorporating socially shared norms and values. But a second important feature is Scott's goal of providing a somewhat general basis for explanation of peasant behavior. He wants to argue that the subsistence ethic is a widely shared set of moral values in traditional rural societies -- with the consequence that it provides a basis for explanation that goes beyond the particulars of Vietnam or Burma. And he has a putative explanation of this commonality as well -- the common existential circumstances of traditional family-based agriculture.
One could pull several of these features apart in Scott's treatment. For example, we could accept the political psychology -- "People are motivated by a locally embodied sense of justice" -- but could reject the generalizability of the subsistence ethic -- "Burmese peasants had the XYZ set of local values, while Vietnamese peasants possessed the UVW set of local values."
This programme suggests several problems for theory and for empirical research. Are there social-science research methods that would permit us to "observe" or empirically discern the particular contents of a normative worldview in a range of different societies, in order to assess whether the subsistence ethic that Scott describes is widespread? Are peasants in Burma and Vietnam as similar as Scott's theory postulates? How would we validate the implicit theory of political motivation that Scott advances (calculation within the context of normative judgment)? Are there other important motivational factors that are perhaps as salient to political behavior as the factors invoked by the subsistence ethic? Where does Scott's "thicker" description of peasant consciousness sit with respect to fully ethnographic investigation?
So to answer my original question -- what kind of concept is the "moral economy"? -- we can say several things. It is a proto-theory of the theory of justice that certain groups possess (18th-century English farmers and townspeople, 20th-century Vietnamese peasants). It implicitly postulates a theory of political motivation and political agency. It asserts a degree of generality across peasant societies. It is offered as a basis for both interpreting and explaining events -- answering the question "What is going on here?" and "Why did this event take place?" In these respects the concept is both an empirical construct and a framework for thinking about agency; so it can be considered both in terms of its specific empirical adequacy and, more broadly, the degree of insight it offers for thinking about collective action.