
19The most extensive account ever, at least in English, of the constitutional doctrine of 'separation of powers', as well as one of the most extensive in English of the idea of 'the rule of law' and its European counterpart, the notion of a 'legal state (German, Rechtsstaat)'. It draws on sources in several languages and disciplines, and many legal systems both ancient and modern. It also proposes a novel basis for judicial independence  outside the tricky sphere of separation of powers.

17Facing Walter's DilemmaRatio Juris 10 (4): 397402. 1997.Jörgen Jörgensen (1938) asks why there should not be a valid deduction even though the premises are imperatives (“Jörgensen’s Dilemma”). Robert Walter (1996; 9 Ratio Juris 168), following Hans Kelsen, thinks that there can be a valid deduction if the premises, although in prescriptive (including imperative) language, are actually descriptions of prescriptions. It is suggested that Walter then has his own dilemma: the more possible it is, for such descriptions to be valid, the less likely it …Read more

10Regular Subgraphs in Graphs and Rooted Graphs and Definability in Monadic Second‐Order LogicMathematical Logic Quarterly 43 (1): 121. 1997.We investigate the definability in monadic ∑11 and monadic Π11 of the problems REGk, of whether there is a regular subgraph of degree k in some given graph, and XREGk, of whether, for a given rooted graph, there is a regular subgraph of degree k in which the root has degree k, and their restrictions to graphs in which every vertex has degree at most k, namely REGkk and XREGkk, respectively, for k ≥ 2 . Our motivation partly stems from the fact that REGkk and XREGkk are logspace equivalent to CON…Read more

9Logics with Zero‐One Laws that Are Not Fragments of Bounded‐Variable Infinitary LogicMathematical Logic Quarterly 43 (2): 158178. 1997.

6Contextsensitive transitive closure operatorsAnnals of Pure and Applied Logic 66 (3): 277301. 1994.We introduce a new logical operator CSTC and show that incorporating this operator into firstorder logic enables as to capture the complexity class PSPACE. We also show that by varying how the operator is applied we can capture the complexity classes P, NP, the classes of the Polynomial Hierarchy PH, and PSPACE. As such, the operator CSTC can be regarded as a general purpose operator. We also give applications of these characterizations by showing that P and NP coincide with those problems acce…Read more

2Monotonicity and the Expressibility of NP OperatorsMathematical Logic Quarterly 40 (1): 132140. 1994.We investigate why similar extensions of firstorder logic using operators corresponding to NPcomplete decision problems apparently differ in expressibility: the logics capture either NP or LNP. It had been conjectured that the complexity class captured is NP if and only if the operator is monotone. We show that this conjecture is false. However, we provide evidence supporting a revised conjecture involving finite variations of monotone problems

2The expressibility of fragments of Hybrid Graph Logic on finite digraphsJournal of Applied Logic 11 (3): 272288. 2013.

The Demise of the Turing Machine in Complexity TheoryIn P. J. R. Millican & A. Clark (eds.), Machines and Thought: The Legacy of Alan Turing, Volume 1, Clarendon Press. 1996.

Sartre, Aron and the Contested Legacy of the AntiPositivist Turn in French Thought, 19381960Sartre Studies International 17 4160. 2011.Taking as its starting point recent claims that JeanPaul Sartre's Critique de la Raison Dialectique was written as an attempt to overcome the historical relativism of Raymond Aron's Introduction à la philosophie de l'histoire, the present article traces this covert dialogue back to a fundamental disagreement between the two men over the interpretation of Wilhelm Dilthey's antipositivist theory of Verstehen or 'understanding'. In so doing it counters a longstanding tendency to emphasise the con…Read more

Kelsen and the Exegetical TraditionIn Richard Tur & William L. Twining (eds.), Essays on Kelsen, Clarendon Press. pp. 12346. 1986.Hans Kelsen’s Pure Theory of Law, presented as a form of legal positivism, is interpreted as establishing metaphysical bases of legal science, on analogy with Kant’s “metaphysical bases of natural science (Metaphysische Anfangsgründe der Naturwissenschaft)”. It is asked, in the light of the Pure Theory’s acknowledged difficulties, how far it succeeds in escaping from the exegetical tradition in Western legal theory.

Raymond Aron and Liberal Thought in the Twentieth CenturyCambridge University Press. 2019.Raymond Aron is widely regarded as the most important figure in the history of twentiethcentury French liberalism. Yet his status within the history of liberal thought has been more often proclaimed than explained. Though he is frequently lauded as the inheritor of France's liberal tradition, Aron's formative influences were mostly nonFrench and often radically antiliberal thinkers. This book explains how, why, and with what consequences he belatedly defined and aligned himself with a French …Read more

Macquarie UniversityRegular Faculty
Sydney, New South Wales, Australia
Areas of Interest
Philosophy of Law 