None of the inventories of the causes of democracy surveyed in Chapter 4 can be taken at face value because they summarize conclusions from disparate and poorly integrated sources of uneven rigor. Before giving credence to checklist items, it is essential to find out from where they came. The remainder of this book therefore evaluates the strengths and weaknesses of the methods and approaches employed by the scholars who have launched these propositions into our collective academic mind.

If there were a way to measure quantities of information, there would be no doubt that the bulk of our knowledge of democratization comes from histories and case studies. It is ironic that noncomparative research so dominates a field known as comparative politics, but this is an irony that is long-standing and well known. The huge number of books and articles about the birth, death, or survival of democracy in dozens of countries in the twentieth century alone is more than any one scholar can digest. In fact, anyone unlucky enough to be buried under this small mountain of printed matter would surely be suffocated and crushed. To be sure, this literature does not satisfy all of the criteria for good theory. I argue in this chapter that histories and case studies produce a kind of knowledge that is unsurpassed in its thickness yet lacking in generality and theoretical integration. In this chapter, I also survey and critique a smaller but still sizable body of literature that consists of comparative histories: detailed comparisons of the historical development of a (usually) small number of cases. Comparative history has enough characteristics in common with case studies and histories to warrant discussing them jointly. Comparative history is a methodological compromise that preserves some thickness while reaching out toward generality and theoretical integration. Those who value thickness would be better off with histories and case studies, those who value generality would be better off with large-sample approaches, and those who value theoretical integration would better focus their efforts on deductive theorizing. Comparative history combines the weaknesses of case studies and quantitative methods when it comes to testing the general truth of a theory. Nevertheless, it has some advantages when the goal is theory development.

On some level, we political scientists think we understand some things about the causes of democratization; we share a conventional wisdom. However, the conventional wisdom is fragmented and not well integrated: it consists of dozens of propositions about the conditions that favor democracy. Although there is a core of propositions that most scholars consider credible, this conventional wisdom is poorly integrated. Some propositions can be grouped into competing schools of thought but, as we consume, interpret, test, and cite the literature, we tend to consider each proposition in isolation, as though it could stand or fall on its own without affecting our belief in other propositions. What passes for the conventional wisdom is not, therefore, an integrated theory of interwoven propositions; the plural, conventional wisdoms would be more accurate. Our collective beliefs about democratization resemble checklists: lists of independent, unconnected items. Checklists are useful for reminding us about all of the varied factors that may be important. Unfortunately, just as a grocery list is not a short story, a checklist is not a coherent and integrated explanation.

There is no official screening committee that certifies that a proposition is generally true and rigorously supported before it joins one of the conventional wisdoms. Rather, our conventional wisdoms are just that: matters of convention. Whatever ideas many scholars have found convincing at one time or another come to be part of what we believe. Because different scholars are convinced by different things, conventional wisdoms are a hodgepodge of ideas originating from diverse sources. To be sure, some propositions have survived repeated testing in large samples using the most rigorous techniques in our toolkits. But many of them are the conclusions of less rigorous studies that were so convincing, in their way, that we have incautiously assumed the conclusions to be generally true. Many comparativists are impressed by intimate knowledge of the politics of a particular country or a region, so the conclusions of case studies and intraregional comparisons sometimes yield insights of a particularly solid kind, and we sometimes elevate these insights to the status of universal truth. Some ideas have been treated as received wisdom since the infancy of comparative politics, when the field was limited to comparisons of Britain, France, and Germany.

In Chapter 3, I argued that the three fundamental goals of research are generality, integration, and thickness and that each of the three main approaches accomplishes one of these goals well and two of them poorly. In Chapter 5, I argued that case studies maximize thickness but do little for generality or integration. In Chapter 6, I argued that formal models and theories pursue theoretical integration, but often at the expense of thickness and generality. In this chapter, I argue that quantitative research achieves generality better than other approaches but tends to be thin and poorly integrated.

More specifically, the goal of quantitative analysis is to estimate the strength and significance of the average impact of one or more independent variables on a dependent variable while holding other variables constant. This kind of analysis is most appropriate for extensive testing, as described in Chapter 7. For example, it is appropriate if one wants to know how much more likely a presidential democracy is to break down than a parliamentary democracy, on average, controlling for level of economic development; how much more democratic one would expect a rich country to be than a poor one, on average, after holding colonial heritage and ethnic fragmentation constant; or whether the typical Latin American country is more democratic than the typical Asian country, other things being equal. Quantitative research is not, however, appropriate for intensive testing, which has the very different goal of determining which theory best explains a single outcome or small set of outcomes. In quantitative analysis, it is accepted that many cases will not be well explained, and this is not considered a problem so long as the average tendency can be estimated well.

Much of our knowledge about politics is factual or descriptive. It requires useful concepts and valid, reliable measurement, as discussed in Chapter 2. Often, it goes beyond describing static, unchanging situations and constructs narrative accounts of specific events. These accounts can be richly detailed, amounting to histories of events and processes that enable us to feel that we understand what happened and why. Much of our understanding of the birth and death of democracies consists of this kind of knowledge. If one wants to understand how democracy evolved in Great Britain, there are hundreds of books that recount the process in exhaustive detail. Most other countries are not quite as well studied, but there are still dozens of books on democratization in Brazil and Japan and even a healthy number of books or articles on relatively neglected cases such as Paraguay, Botswana, Sri Lanka, and Mongolia. The knowledge contained in these works is essential and extremely valuable; it is a scholarly achievement that deserves greater appreciation.

This literature is so massive that it would be foolish to attempt to summarize it in this book. Instead, I focus here on attempts to develop a theoretical understanding of democratization, which is a quite different kind of knowledge. I do not argue with readers who prefer an idiographic, every-case-is-unique understanding to any attempt to develop a nomothetic, or theoretical, understanding. However, those who seek a theoretical understanding must develop and test theory.

Why are some countries democracies while others are not? Why do some democracies survive while others fail? These are core questions in political science, sociology, history, and economics. Scholars have been trying to answer them ever since Aristotle. After 2,500 years of research, what do we know? How do we know it? This book answers the latter two questions.

Rationale

After so much has been written on these matters, I am obliged to explain why we need this particular book on democracy. The answer is simple: to distill this vast literature down to a comprehensible critical survey! Democratization has been studied for so long and in so many different ways that the literature is overwhelming and bewildering. It encompasses ideas borrowed from the study of early modern Europe, strategic bargaining games, Asian cultures, measurement theory, public opinion about economic trends, legacies of colonialism, geographic networks, theories of class struggle, demographic trends, war and peace, and many other phenomena. There are dozens of hypotheses about the causes of democracy (Chapter 4 summarizes fifty-five of them). The first step toward digesting this mountain of scholarship is taking a comprehensive inventory of all the possible explanations.