Extending Deontic Logic for the Formalisation of Legal Rules

This book is an adaptation of my PhD thesis Representing L3gVI Rules in Deontic Logic [Royakkers, 1996]. The main alterations are: • The addition of chapter 2 concerning the semantics of deontic logic based on valua­ tions. In this chapter I extend the Beth tableau method, which is originally developed for the propositional calculus, to also be applicable for deontic logic. For those who are not familiar with deontic logic or with the axiomatic deduction, this method is a useful tool to check whether a formula is valid or not. • The addition of the notion of commitment in chapter 5, and the notion of weak and strong permission in chapter 7. • The omission of the chapter concerning defeasible deontic logic, of which a revised version is published in [Nute, 1997]. • Chapter 6 has been revised rather thoroughly. Here I introduce the logic of enact­ ment based on epistemic logic and local reasoning to express normative inconsis­ tencies in a consistent way. I wish to thank John-Jules Meyer, Giovanni Sartor and Marek Sergot for their suggestions and criticisms of my PhD thesis, which have improved this book. Heleen Neggers and Jan Draisma deserve credit for the layout. Special thanks go to Frank Dignum for his continuous support and inspiring sugges­ tions. v Contents 1 Introduction 1 1.1 Logic and law. . . . . . . . . . . . . . . . . . . . . . .. . . . 1 . . . 1.2 Conflicting speed limits . . . . . . . . . . . . . . . . . . .. . . . 3 . .