 The leading social-scientific accounts of judicial decision-making—both the informal ones (Pritchett 1949; Powe 2000) and the formal ones (Segal &amp; Spaeth 1993)—have two striking features in this regard. First, they all aim to account for the relative causal contribution of “law” and non-law factors (e.g., political ideologies or “attitudes”) to judicial decisions. Second, they demarcate “law” from non-law factors in typical Hard Positivist terms, i.e., they generally treat as “law” only pedigreed norms, like legislative enactments and prior holdings of courts (as well as, sometimes, the interpretive methods applied to these kinds of legal sources: see the treatment of the “legal model” in Segal &amp; Spaeth 1993, pp. 33–53). If these models were ultimately vindicated empirically—and not just for American courts—this would give the Replacement Naturalist reason to abandon any a priori, intuitive confidence we had about the concept of law that conflicted with Hard Positivism—just as the role of non-Euclidean geometry in parts of physics has led everyone to repudiate Kant’s a priori intuitive confidence about the Euclidean structure of space. If social science really cuts the causal joints of the legal world in Hard Positivist terms, the Replacement Naturalist argues, that is a compelling reason to work with that concept of law as against its competitors.