This paper offers a critical reconsideration of the traditional doctrine that responsibility for a crime requires a voluntary act. I defend three general propositions: first, that orthodox Anglo-American criminal theory (as represented by Michael Moore's updating of Austin's volitionalism) fails to explain adequately why criminal responsibility requires an act. Second, when it comes to the just definition of crimes, the act requirement is at best a rough generalization rather than a substantive limiting principle. Third, that the intuition underlying the so-called “act requirement” is better explained by what I call the “practical-agency condition,” according to which punishment in a specific instance is unjust unless the crime charged was caused or constituted by the agent's conduct (broadly understood) qua practically rational agent. The practical-agency condition is defended as a reconstruction of what is worth retaining in Anglo-American criminal law's traditional notion of an “act requirement.”

This essay examines the ambition to taxonomize law and the different methods a legal taxonomer might employ. Three possibilities emerge. The first is a formal taxonomy that classifies legal materials according to rules of order and clarity. Formal taxonomy is primarily conventional and has no normative implications for judicial decision-making. The second possibility is a function-based taxonomy that classifies laws according to their social functions. Function-based taxonomy can influence legal decision-making indirectly, as a gatekeeping mechanism, but it does not provide decisional standards for courts. Its objective is to assist in analysis and criticism of law by providing an overview of the body of legal doctrine. The third possibility is a reason-based taxonomy that classifies legal rules and decisions according to the moral principles or “legal principles” thought to justify them. Reason-based taxonomy of this type offers courts a set of high-level decisional rules drawn from legal data. Its objective is to guide courts in deciding new cases and evaluating precedents. A predominantly formal taxonomy facilitates legal analysis and communication. A functional taxonomy can assist those who make and apply law by providing a purposive overview of the field. Reason-based taxonomy may be useful to lawmakers but is unhelpful when offered as a guide to adjudication of disputes.

In 1966 the U.S. Supreme Court wrote, “The basic purpose of a trial is the determination of truth.” This is Larry Laudan's guiding premise in his “essay on legal epistemology.” Without ascertaining the facts about a crime, he writes, it is impossible to achieve justice, since a just resolution crucially depends on correctly figuring out who did what to whom. Thus, he continues, “it is entirely fitting to ask whether the procedures and rules that govern a trial are genuinely truth-conducive.” In chapter 1 of the book, Laudan identifies one of the most important and legitimate methods for finding truth, namely, ensuring that the jury hears all and only relevant evidence. Laudan bemoans the fact, however, that “legal texts and the practices of courts routinely flout” this principle. Much of the rest of the book is devoted to the other tests for admissibility that the system imposes, tests that Laudan often regards as misguided.