In this chapter, I explore what is involved in the idea of the “discriminatory power of the evidence” and what determines the margin by which that power must favor the claimant (assumed here to be the party bearing the burden of persuasion) in order to warrant a positive verdict. To do this, we consider the nature of a verdict itself and its relationship to the goals of adjudication (§ 2.1). This will lead naturally to the well-known decision-theoretic model specifying the degree of discriminatory power necessary for a verdict (§ 2.2). By briefly examining two competing theories of discriminatory power, I will show how certain contemporary debates about the viability of the decision-theoretic model are largely tangential to the issues addressed in subsequent chapters, though they place those issues in clearer context (§ 2.3). Theories of discriminatory power are also related to complex questions about how the inference process can be understood, modeled, or described (§ 2.4), and they must recognize the importance of background information, information that is not part of the evidence formally presented (§ 2.5). I explore these ideas and hope thereby to contribute to our understanding of discriminatory power. But I emphasize that this is not my primary purpose. Rather, these ideas simply serve as a backdrop for the critical discussion of Keynesian weight in the following chapters.

Practical Reasoning in the Adjudicative Context

Verdicts seem declaratory in the sense that they declare certain facts to be true or false. But these declarations are not made in a vacuum; they are not idle speculations. The facts declared in adjudication very often, though not always, entail the attribution of the breach of serious social obligation, and almost always, serious consequences attach to them. So it would be more precise to say that verdicts declare that certain facts are to be taken as true for the serious purposes of such application.