Theorizing how interventions work in evaluation: Process-tracing methods and theorizing process theories of change

This article argues for the importance of theory and theorizing for an evaluation in the form of a process theory of change. A process theory of change centers its theoretical attention on key episodes that explain how things worked, in which the causal linkages are unpacked. The key lies in answering why actors do what they do (and thus whether these actions can be traced back to the intervention). This theorization has three steps: (1) definition of intervention and potential contribution; (2) theorization of potential contribution pathways; and (3) unpacking the process. This procedure is illustrated with a hypothetical example.