Causation is commonly defined using the counterfactual model, and the “but-for” standard in particular. It asks whether the harm suffered by the plaintiff would have occurred in the absence of the defendant’s act. It is commonly believed, however, that the counterfactual model fails in cases involving multiple sufficient causes—that is, cases in which two or more forces contribute to an outcome where each force alone would suffice to produce the same outcome. This paradox has, over time, pushed causation standards into a state of ambiguity and disarray as courts have attempted to retain the counterfactual model as the appropriate framework for causation while abandoning it in multiple-sufficient-cause situations to attain the sought-after outcome.

In this article, I argue that, contrary to common understanding, the counterfactual model does not fail in multiple-sufficient-cause situations. In particular, I propose the adoption of a framework for cause and effect in statistics and the sciences called the “potential outcomes framework,” and I apply it to explain and address the apparent paradox of multiple sufficient causes. I then extend my analysis to show a broad range of implications for fields such as torts, criminal law, contracts, constitutional law, and employment discrimination. Beyond demonstrating important consequences for standards of causation in various substantive areas of the law, I show how my analysis affects our understanding and treatment of timely issues, such as the judicial interpretation of causal language in criminal statutes and the permissibility of “mixed-motive” cases under Title VII and other federal discrimination laws.

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Arizona State Law Journal

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