Observing Causal Mechanisms with Process-Tracing Methods – The Benefits of Using a ‘Mechanism’ Understanding of Causality

Abstract

What type of understanding of causality should be used in process-tracing case study research? We contend that process-tracing methods will profit from adopting a ‘mechanistic’ ontology of causation, where a theorized causal mechanism is conceptualized as a series of interacting parts composed of entities that undertake activities that transmit causal forces from the explanatory variable(s) through a mechanism to produce a given outcome Y. In this understanding, we argue that the each of the parts of a causal mechanism should be treated as necessary parts that have to be present in a given case, thereby also enabling causal inferences to be made in a single case design when coupled with Bayesian logic. However, process-tracing is not a panacea for everything, and as we will expand upon, causal inferences can only be made using process-tracing methods as regards whether the individual parts of a mechanism are necessary and whether a causal mechanism is sufficient to produce an outcome in a specific case. We illustrate the promise and difficulties with the proposed process-tracing methodology by conceptualizing and operationalizing the bureaucratic politics theory of foreign policy.