It's all about mechanisms – what process-tracing case studies should be tracing

ABSTRACT

Process-tracing (PT) as a distinct case-study methodology involves tracing causal mechanisms that link causes (X) with their effects (i.e. outcomes) (Y). We trace causal mechanisms whereby a cause (or set of causes) produces an outcome to both: (1) make stronger evidence-based inferences about causal relationships because the analysis produces within-case evidence of each step of the causal process (or absence thereof) in between a cause and outcome, and (2) because tracing mechanisms gives us a better understanding of how a cause produces an outcome. Yet, when we look at the methodological literature on PT, there is considerable ambiguity and discord about what causal mechanisms actually are. The result of this ambiguity and discord about what mechanisms are clearly maps onto existing applications of PT, with most PT case studies completely ignoring the underlying theoretical causal processes. In the few PT applications where mechanisms are unpacked, they are typically only developed in a very cursory fashion, with the result that there is considerable ambiguity about what theoretical process the ensuing case study actually is tracing. If we want to claim we are tracing causal mechanisms, the causal processes in between X and Y need to be unpacked theoretically. How can we claim we are tracing a causal ’process’ when we are not told what the process (i.e. mechanism) actually is? To alleviate this problem, the article attempts to develop a clearer definition of causal mechanisms to provide scholars with a framework for theorising mechanisms in a fashion that is amenable to in-depth empirical analysis using PT.

KEYWORDS:

• Causal mechanisms
• causation
• process-tracing
• within-case evidence

Disclosure statement

No potential conflict of interest was reported by the author.

Notes on contributor

Derek Beach is an associate Professor of Political Science at the University of Aarhus, Denmark. He has published two books on case-based methods with the University of Michigan Press, along with numerous methodological articles on process-tracing. His substantive research deals with European integration, focusing in particular on tracing the role of institutions in high-level negotiations in the EU. He is the academic co-convenor of the ECPR Method Schools.

Notes

1. Indeed, given that many scholars understand the term ‘process’ to denote non-causal, narrative analysis, it might be more appropriate to use the term ‘Mechanism-Tracing’ instead to accurately describe what we should be doing in PT if we have the ambition to study causal processes. To avoid more jargon, this article sticks with the well-known PT term.

2. Additionally, observations within a single case over time cannot be treated as independent, given that what happens at t₀ naturally impacts on what happens at t₁.

3. In assessing hundreds of articles from top journals in the past decade, the author has found precious few examples of case studies that explicitly theorize causal process in between X and Y. Therefore, when compared to almost all of the existing article-length research, Ziblatt's study provides us with much more theoretical information on the causal process than is typical. But this does not mean that Ziblatt's theorized mechanism could not be improved further (see below).

4. Note that there is considerable debate about whether this use of Bayesian logic should be formalized in terms of quantified probabilities, or used in a more informal, Folk Bayesian fashion as in law. For more on this discussion, see Beach and Pedersen (2016).