Defeasible legal concepts and judicial argumentation

This chapter takes its cue from Hart’s pioneering essay “The Ascription of Responsibility and Rights” to examine some problems related to defeasible legal concepts. More to the point, I will take up the following questions: Does the defeasibility of legal concepts imply that it is never possible to define these concepts as a list of necessary and sufficient conditions? And does this imply that the judicial conclusion according to which a certain legal concept is applicable does not deductively follow from a description of such conditions? If so, is this tantamount to claiming that legal argumentation is (or must be represented as) non-monotonic? I answering such questions, will attempt to argue that even if all legal concepts are defeasible, and therefore cannot be defined through a list of necessary and sufficient conditions, this does not imply that judicial argumentation should be represented as non-monotonic.