Formalizing and Falsifying Causal Pathways of Rare Events

Building on recent formalizations of root cause analysis for rare events (“outliers”) in structural equation models, we propose a formal definition of a causal pathway and discuss its testable implications. We identify conditions under which these implications depend only on a causal abstraction defined by the pathway of rare events, rather than on the full causal graph of the underlying system. Accordingly, we introduce an abstraction of causal structure to pathways of rare events that bridges simple verbal causal explanations and detailed causal modeling.

This paper introduces a framework for causal explanations of rare events. We represent an explanation as a causal pathway: a structured set of events and mechanisms leading to a target outcome. The framework introduces scores that quantify how strongly a proposed pathway explains the outcome and how accurately a simplified pathway represents a more detailed causal model. These scores can be used to quantitatively evaluate causal explanations, compare alternative explanations, and identify weak or inconsistent parts of a proposed causal account.