H.L.A. Hart, answered from the texts and cited to the page.
A theory of law can be both general (applicable to legal systems across times and places) and descriptive (not committed to the value-judgements of those whose legal systems it describes). This is the position I defended in the Postscript and the position The Concept of Law was always meant to develop. The hermeneutic insight — that to understand a legal system one must understand the internal point of view of the officials who accept its rule of recognition — does not require the theorist to share that point of view.12
The descriptive jurist takes full account of the meaning of legal rules to those who accept them; she understands what is doing what for them; she may render that understanding into theoretical form without herself committing to the moral worth of what she renders. Joseph Raz's distinction between detached and committed statements of legal rights and duties is the formal apparatus: a detached statement reports what the system requires from the participant's point of view without endorsing the system; a committed statement reports the same thing from inside one's own acceptance of the system.34
The descriptive jurist makes detached statements. Dworkin's claim in Law's Empire that legal theory must be interpretive — that the only intelligible theory of a legal system is one that constructs the most attractive version of that system the materials will support — conflates the participant's task with the theorist's.5
It is true that for this purpose the descriptive legal theorist must understand what it is to adopt the internal point of view and in that limited sense of he must be able to put himself in the place an insider; but this is not to accept the law or share or endorse the insider's internal point of view or in any other way to surrender his descriptive stance.The Concept of Law, p. 243
For the understanding of this the methodology of the empirical sciences is useless; what is needed is a 'hermeneutic' method which involves portraying rule-governed behaviour as it appears to its participants, who see it as conforming or failing to conform to certain shared standards.Essays in Jurisprudence and Philosophy, p. 20
The first of these is the distinction between a- normative TM See his Practical Reason and Norms (London 1975), esp. 123-9, 146-8, 162-77; The Authority of Law (Oxford 1979), 153-7; The Concept of a Legal System (2nd edn., Oxford 1980), 234-8.Legal Duty and Obligation, p. 161
This conception of a detached normative statement is in principle a successful explanation of what is left unexplained in other theories which insist that rights and duties have the same meaning in legal and moral contexts; and it shows how it can be the case that normative statements may be used in describing the law by those who in no way endorse or accept it as guides or standards of conduct.Legal Duty and Obligation, pp. 162–163
This latter claim is in my view mistaken and I give below my reasons for objecting to any such interpretive version of my theory. But in his books Dworkin appears to rule out general and descriptive legal theory as misguided or at best simply useless.The Concept of Law, p. 242
The descriptive-interpretive debate is the central methodological battlefield of post-1980 jurisprudence. Dworkin's Law's Empire (1986) advanced the interpretive theory; the 2001 Hart Lecture went further, confessing Dworkin's inability to see how any social-theoretical practice (legal theory included) could fail to express a value-commitment. The Postscript reply defends the descriptive possibility. Raz's detached-vs-committed distinction supplies the apparatus. Perry, Coleman, Leiter, Dickson, and others have developed the methodological argument in various directions. The post-positivist tradition (MacCormick, Finnis in some readings) holds that the descriptive method is unsustainable in its strong form but salvageable in a weaker one. The debate is unsettled.