Metascience DOI 10.1007/s11016-015-0009-x BOOK REVIEW

Causal mechanisms in political science Andrew Bennett and Jeffrey T. Checkel (eds.): Process tracing: From metaphor to analytic tool. Cambridge: Cambridge University Press, 2015, 342pp, $36.99 PB, $99.00 HB Rosa W. Runhardt1

 Springer Science+Business Media Dordrecht 2015

Philosophers of social science have emphasized mechanistic approaches to causal inquiry for some time now, showing why focusing on the mechanisms behind correlations is preferable to focusing on correlations alone (cf. Johnson 2006; Little 1991; Reiss 2007, 2009; Steel 2004; see also King et al. 1994 for an example of purely correlational research). In Process Tracing, political scientists Andrew Bennett and Jeffrey Checkel present a concrete method for finding evidence of causal mechanisms, process tracing. Process tracers give evidence for causal relations in terms of the observable implications of the underlying causal mechanisms through which a putative cause affects some effect of interest. Such observable implications often take the form of a chain of events, or process, which connects cause and effect. Though Process Tracing contains applications of mechanistic reasoning unfamiliar to philosophers, and as such will be of interest to those working in the mechanist tradition, Bennett’s and Checkel’s own discussion of the philosophical foundations of process tracing is limited. The reader will have to delve deep into the volume’s contributed chapters for links between the literature on causation and this new method. Process Tracing is the first book that is entirely devoted to a systematic analysis of process tracing, though earlier publications have mentioned the method (Bennett and George 1997; George 1979; George and Bennett 2005). The book is set up as follows. Bennett and Checkel set out the main themes of the book in a significant introductory chapter. There they argue for process tracing as the best tool to find evidence of causal mechanisms and establish ten ‘‘best practices’’ to judge what makes any particular study an instance of good process tracing. In subsequent chapters, contributing experts either describe how process tracing is used in their particular subfield, such as the study of international institutions, European & Rosa W. Runhardt [email protected] 1

London School of Economics and Political Science, London, UK

123

Metascience

integration, or the end of the Cold War, or argue for particular changes to Bennett’s and Checkel’s best practices. Finally, the concluding chapters present how process tracing can be integrated with other methods in multi-method research, and contain Bennett’s and Checkel’s summary of the recommendations proposed by the contributing experts. Bennett’s and Checkel’s main contribution in their introduction is not their description of the history of process tracing or their discussion of its philosophical foundations (mechanistic social causation), both of which are brief. Instead, their main contribution is the presentation of their ten best practices for reliable process tracing, which build upon the postulated philosophical basis. One should, I would argue, see this book in the light of the recent trend in other areas of philosophy of social science to ‘‘analyse the sources of [a method’s] reliability, rather than the metaphysical … conditions of its possibility’’ (Tal 2013, 1168). The ten best practices Bennett and Checkel propose centre on two main themes. First, the authors argue that process tracers ought to deduce the observable implications of both (1) the mechanism they hypothesize connects cause and effect, and (2) alternative mechanisms for this connection postulated in the literature. This recommendation is meant to solve the problem of ‘‘equifinality’’, i.e. the same social outcome could have been the result of different causal mechanisms. The second theme Bennett and Checkel focus on is the quality of the evidence used to corroborate some causal mechanism’s presence in a particular case study. For instance, they give several recommendations for how to avoid biased reporting and how to justify the boundaries established around a case study (e.g. what to take as the first and last event in some historical episode, or when to stop collecting data). Although Bennett’s and Checkel’s description of causal mechanisms draws links to previous methodological literature, perhaps as a result of focusing so squarely on political science practice, their description of causal mechanisms is quite disconnected from debates in the philosophy of social science (e.g. Little 2011). This is the main drawback of Bennett’s and Checkel’s own contributions to the book: closer engagement with the philosophical literature could have helped the authors solve some of the key problems they are concerned with. To illustrate, consider the generalizability of causal mechanisms, an issue which comes up in several chapters. In Chapter 3, for instance, Checkel himself regrets that ‘‘the causal mechanisms at the heart of process-tracing accounts are not readily integrated into broader, more generalizable theories; the theoretical take-away of carefully executed process tracing is often little more than ‘endless lists of casespecific causal mechanisms’’’ (Bennett and Checkel 2015, 262). Bennett and Checkel repeat this sentiment in their conclusion without trying any further to find a solution. However, though methodologists have not researched the relation between more general theories and case-specific processes in detail, philosophers of science have written on these issues. To name but two, both Little (1993) and Steel (2008) discuss how generalizations and mechanistic reasoning relate. Both texts could have provided important insights for Bennett’s and Checkel’s analysis. In the second part of the book, contributing authors assess the strengths and weaknesses of applications of process tracing for their particular subfield. They do so both through the analysis of ‘‘cutting-edge’’ examples of process-tracing studies

123

Metascience

and through discussions of the mechanisms postulated in particular subfield theories, including cognitive or structural theories. Of these chapters, of particular interest are those which add to the best practices outlined in the introduction by engaging more closely with the philosophical literature than Bennett and Checkel do. For instance, Chapter 5, by David Waldner, will be of interest to philosophers because he combines process tracing with causal graph analyses, which fits well with familiar theories from the philosophy of causation (cf. Pearl 2000; Woodward 2002, 2003). Similarly, Chapter 7, by Jason Lyall, introduces additional best practices which will be familiar to philosophers of causation: Lyall amongst others argues for establishing counterfactual support for the processes traced, a move which has parallels in the philosophical literature on mechanisms (cf. Psillos 2004; Runhardt 2014). Of the later chapters, Tad Dunnig’s comparison in Chapter 8 between the use of natural experiments and process tracing is of particular interest, as is Andrew Bennett’s Appendix to the book, in which he analyses process tracing in terms of Bayesian inference. The chapters above all share a deeper engagement with the philosophical literature. Philosophy of causation at its best provides concrete recommendations for practice, and these chapters illustrate this. Thus, though the editors of Process Tracing do not extensively engage with the literature that philosophers of social science would think of when asked to discuss causal mechanisms, the rest of the book partially makes up for this. This book will also be of interest to philosophers of social science for another reason: political science is one of the least discussed special sciences, and as such, the concrete examples of mechanistic reasoning in this book add a dimension that philosophers may otherwise not consider. The logical next step would be to connect the research from this volume with the recent trends in philosophy of social science. Such interdisciplinary work will help both methodologists and philosophers: philosophical theories of causation have a direct impact on the feasibility of the process-tracing method, and by investigating a popular contemporary method in the social sciences we can examine to what extent our philosophical theories of causation are workable in practice.

References Bennett, Andrew, and Jeffrey T. Checkel. 2015. Process tracing: from metaphor to analytic tool. Cambridge: Cambridge University Press. Bennett, Andrew, and Alexander L. George. 1997. Process tracing in case study research. In MacArthur Foundation Workshop on Case Study Methods, Belfer Center for Science and International Affairs, Harvard University, October 17–19. George, Alexander L. 1979. Case studies and theory development: The method of structured, focused comparison. In Diplomacy: New approaches in history, theory, and policy, ed. Paul G. Lauren, 43–68. New York: Free Press. George, Alexander L., and Andrew Bennett. 2005. Case studies and theory development in the social sciences. Cambridge: MIT Press. Johnson, James. 2006. Consequences of positivism: A pragmatist assessment. Comparative Political Studies 39(2): 224–252. King, Gary, Robert O. Keohane, and Sidney Verba. 1994. Designing social inquiry: Scientific inference in qualitative research. Princeton: Princeton University Press.

123

Metascience Little, Daniel. 1991. Varieties of social explanation: An introduction to the philosophy of social science. Boulder: Westview Press. Little, Daniel. 1993. On the scope and limits of generalizations in the social sciences. Synthese 97(2): 183–207. Little, Daniel. 2011. Causal mechanisms in the social realm. In Causality in the sciences, ed. Phyllis McKay Illari, Federica Russo and Jon Williamson, 273–295. Oxford: Oxford University Press. Pearl, Judea. 2000. Causality: Models, reasoning, and inference. Cambridge: Cambridge University Press. Psillos, Stathis. 2004. A glimpse of the secret connexion: Harmonizing mechanisms with counterfactuals. Perspectives on Science 12(3): 288–319. Reiss, Julian. 2007. Do we need mechanisms in the social sciences? Philosophy of the Social Sciences 37(2): 163–184. Reiss, Julian. 2009. Causation in the social sciences: Evidence, inference, and purpose. Philosophy of the Social Sciences 39(1): 20–40. Runhardt, Rosa W. 2014. Evidence for causal mechanisms in social science: Recommendations from Woodward’s manipulability theory of causation. Philosophy of Science. Steel, Daniel. 2004. Social mechanisms and causal inference. Philosophy of the Social Sciences 34(1): 55–78. Steel, Daniel. 2008. Across the boundaries: Extrapolation in biology and social science. Oxford: Oxford University Press. Tal, Eran. 2013. Old and new problems in philosophy of measurement. Philosophy Compass 8(12): 1159–1173. Woodward, James. 2002. What is a mechanism? A counterfactual account. Philosophy of Science 69(S3): S366–S377. Woodward, James. 2003. Making things happen: A theory of causal explanation. Oxford: Oxford University Press.

123