As for that attention to fact which positivists think a virtue of their method, it is fully present and operational in any adequate philosophy of law (natural law theory). For practical reason advances in deliberation towards choice (whether concretely or more universally and abstractly, ―philosophically‖), and does so by the use not only of normative premises about the good and the right but also, indispensably, of factual premises about the conditions in which the good can be attained or would be harmed. The truth of those premises has to be earned, by rigorous attention to facts, experience, the typical, the likely, the physically, biologically or psychologically possible, and so forth.
In short: the philosophy of law is best pursued without reliance on such equivocal labels as ―positivist‖. Should we also dismiss the label ―natural law theory‖? Any sound theory or philosophy of law will need to attend to two broad kinds of principle, norm and standard: those applicable by persons of practical reasonableness only because of they are standards chosen or otherwise factually established by past choices of their community, and those that are applicable whether or not so chosen or ratified. For the latter, the history of our civilization has adopted the name ―natural law‖. The adoption can be traced to Plato‘s engagement with the Sophists‘ theory that more or less egoistic strength and cunning naturally, and so to say ―by right‖ and reasonably, hold sway in human deliberation. Plato‘s brilliant recapturing of ―right by nature‖ from this sophistical error14 has been decisive for our vocabulary, making its way through Aristotle, the Stoics, Cicero, St Paul, Gaius and Aquinas and their successors down to the United Nations Charter15 and today. There is no symmetry of unserviceability between the labels ―positivism‖ and ―natural law theory‖, though the latter, to be sure, labours under misinterpretations as grave as the Sophists‘ and further tangled by a long civilizational sequence of reversions, accretions and quasi-philosophical flotsam and jetsam.
A main reason for wanting to introduce positive law and the Rule of Law is to resolve disputes within a political community about what morality (especially justice) requires, recommends, or permits. There is thus good reason to introduce a way of thinking – call it legal thinking – in which (within undefined but important limits) the sheer fact that a legally (―constitutionally‖) authorized person or body of persons has pronounced its determinatio16 of some disputed or disputable issue is taken as sufficient ground for affirming the legal validity of the determinatio and its propositional product (rule, judgment, etc.). In this way of thinking, issues of the justice or injustice of the determinatio, once it has been made, are pushed to the margins of the legal domain. Only when moral extremes are approached do questions of justice and morality become once again relevant. Thus talk of ―validity‖ can be more or less fully and cleanly reserved to intra-systemic legal (positive-law) discourse, and taken to entail not moral but legal obligatoriness (an obligatoriness not to be understood reductively as merely liability to penalty or punishment).17
Natural law theory has no quarrel with – indeed, promotes – a distinction or bifurcation between intra-systemic [legal] validity (and obligatoriness) and legal validity (and obligatoriness) in the moral sense18. Indeed, it is not unreasonable to see such a distinction at work in the famous tag ―An unjust law is not a law‖. Such a way of speaking is not self-contradictory, paradoxical, or even remarkable: ―an insincere friend is not a friend‖; ―a logically invalid argument is no argument‖; ―a quack medicine is no medicine‖... So too in the famous tag or theorem: ―unjust law‖ (lex iniusta) here refers to an intra-systemically valid legal rule or order,19 and ―not law‖ (non lex) signifies that, moral limits having been transgressed, this same law lacks validity (as law) in the moral sense (i.e. legitimacy) and thus, as such,20 lacks moral obligatoriness.
