Why write a book like this one? There are three reasons. First, I want to make the subject understandable to those who work with it— students, practising lawyers, legal academics, administrative decision- makers, legislators and judges— and comprehensible to those outsiders who wish to know more. Demonstrating that there is an intelligible structure to what might look at first glance like a random collection of discrete rules and standards gathering like barnacles on the hull of a shipwreck will help people to grasp administrative law. Second, theoretical work is useful in rationalising the rapid development of administrative law since the latter half of the 20th century.1 In a sense, tort and contract have a one- hundred year headstart on administrative law. Those areas of law were liberated from the constraints of the writ system in the late 1800s, a full century before the so- called ‘prerogative writs’— the predecessors of today’s ‘application for judicial review’— were abolished or tamed. Administrative lawyers have some catching up to do. Indeed, administrative lawyers have been accused of creating a subject which has the ‘core’ of a ‘seedless grape’.2 Think of this book as an attempt to answer the ‘seedless’ gripe.