  Rules of law are propositions of practical reason, apt for being taken as directive in the deliberations of law’s individual subjects towards judgment, choice (decision), and action (including chosen forbearance). So a sound theory of law will have an integrated and critical understanding of the structure of chosen action, particularly of the relationships between the intending of ends, the adoption of means, the dual character of almost all ends as also means, and of almost all means as also ends, and the necessity and normal possibility of freely choosing between options which embody or promise benefits and disadvantages incommensurable (incompletely commensurable) (Finnis 1997) with the benefits and disadvantages of the alternative options. Such an understanding will clarify the often somewhat crude accounts given in criminal law dogmatics (case law and textbooks) of actus reus andmens rea, accounts which often fail to distinguish been action as a physically or conventionally demarcated chunk of behavior and action as the carrying out of the choice of an option, that is of a proposal shaped and thus given a privileged description in the deliberations of the acting subject. The difference between intended or chosen means (or ends) and foreseeable or even fully foreseen effects (“side-effects”), like the consequent difference between the moral and, presumptively, legal standards applicable respectively to intended and not-intended effects, is psychologically and morally real. But it is often distorted by a simplistic legal dogmatics too averse to the (very real) risk that defendants will prevaricate about what they had in mind. What counts, and can often be inferred despite prevarication, is the act-description under which the behavior chosen was attractive to the defendant in his or her actual deliberations (as distinct from rationalizing act-descriptions adopted to present that motivation in a better light).