Invariant causal mechanisms

Qualitative methodologists generally treat process tracing methods and a mechanistic view of causation as natural allies. Two conjoined propositions form the basis for this alliance. The first proposition is that the identification of causal mechanisms is the sine qua non of distinguishing causal relations from mere correlations. The second proposition is that process-tracing methods are uniquely qualified to identify these critical causal mechanisms. In one admirably pithy formulation, Gary Goertz and James Mahoney state categorically: “No strong causal inference without process tracing.” There appears to be a tacit consensus that process tracing is both necessary and sufficient for causal inference.