Sheri Berman raises some important questions about our book The Narrow Corridor. She asks how the “strength of society” should be measured. She proceeds to suggest that measuring the density and nature of its civil society organizations is one promising idea. We agree and gave several instances of what we mean by the strength of civil society in the book; for example, in our discussion of Charles Tilly’s (1995) book Popular Contention in Great Britain, where he shows how society formed different types of associations and organizations in response to the threats created by the eighteenth-century British state. This measure coincides with Berman’s intuition. But we did not want to equate the strength of society with Western-type notions of civil society. Society in Yemen is strong, but it does not look like the Western notion. Rather, it is organized around lineages and extended kin groups, or “tribes.” Similarly, as we also discussed in the book, in Africa, society was organized by secret societies, age sets, and title associations: even if these do not look like civil society, they provide a rich set of empirical patterns relevant for understanding the strength of society.

Berman also asks whether one should probe more the different natures of society. For example, society can, in addition to being strong, be “divided and polarized” in ways that make it very difficult for it to check the power of the state. That is exactly our theory in fact, especially as we explain in detail in the context of India in chapter 8. Indian society was “strong” in an organizational sense in many ways, but as we show there, it was divided against itself along the lines of caste. As a result, it could not do an effective job of balancing the state. This is where our argument about the “Red Queen effect” comes in. When we talk about the strength of society, we are factoring in how the nature of society alters endogenously in the course of its struggle with the state, especially in the corridor.

Do we underemphasize democracy? We do not think so. But we do not equate society’s organization and strength with democracy. That might appear natural from a European perspective, but it is not justified by the history of many non-European places, where societies could be organized and rulers kept in check, even if they did not look like a typical democracy. Even in Europe, as our argument in chapter 6 illustrates, society’s strength long predates the types of institutions we typically associate with democracy.

Finally, Berman asks, Do we have a theory? It is useful to ask first what Berman means by a “theory.” Some social scientists equate a theory with a holistic explanation for the phenomenon at hand. Some go further and want the main drivers in the theory to be “exogenous” factors, such as geography, endowments, or historically predetermined events. We do not think this is the right way to think about a theory. Explaining a phenomenon such as democracy with agricultural conditions that favor wheat is no more or no less a theory than an approach that emphasizes the nature of political coalitions or the role of leaders but at the same time points out when different types of coalitions are more likely (but definitely not certain) to emerge. More fundamentally, a theory, as we understand it, is all about clarifying mechanisms, so that we can think about the phenomenon of interest in a more nuanced way and answer questions about why something has or has not happened. This again highlights the importance of “comparative statics”: What are the characteristics that make this phenomenon more or less likely to happen?

According to these criteria, our entire book is centered on a theory and is about developing this theory. First, we propose a new mechanism. We argue that the roots of liberty and institutions, such as democratic ones, that protect liberty and keep elites in check lie in the balance of power between state and society. Second, we explain, at least in broad terms, how path dependence and specific societal choices in the relevant historical circumstances shape the trajectories of nations. Think, for example, of our account of how the conjunction of the collapse of the Western Roman Empire and the bottom-up politics of the Frankish tribes that filled the ensuing void created new opportunities that were exploited by leaders such as Clovis and Charlemagne and how this created a path-dependent process of evolution of states and societies in the corridor. Finally, as we recount in chapter 9, our approach delivers some powerful and unique comparative statics; for instance, emphasizing how the same set of circumstances will lead to divergent outcomes in terms of despotism, statelessness, or liberty depending on the prevailing balance of power.