The Meaning of Constitutional Terms: Essential Features, Family Resemblance and Theory-based Approaches

Categorisation is fundamental to legal decision making. In constitutional law, jurists must regularly decide whether or not laws and facts fall within the categories defined by the Constitution: is this law a law ‘with respect to ... taxation’?1 Is that corporation a ‘trading corporation’?2 Is performance of this function an exercise of ‘judicial power’?3 Is that nation a ‘foreign power’?4 For the most part, however, judges and legal advisers approach categorisation unreflectively. They observe that their practices work; they assume that their practices are coherent. In this article, I draw on the extensive literature in psychology and cognitive science to encourage jurists to rethink some of their assumptions about how they go about the business of categorisation. In particular, I argue that what judges do is often rather different from what they say that they do. The standard semantic model that Australian judges use, in constitutional cases to resolve categorisation questions, is the connotationdenotation model. That model rests on several propositions. One is of particular interest here. That is the proposition that the meaning of a constitutional term (its connotation) is determined by a set of necessary and sufficient features. A person, purpose or activity falls within the meaning of the term if, and only if, it possesses all of the ‘essential features’ or ‘essential characteristics’ that define