Law, philosophy of

1. Law as reason

In the Republic, Plato depicts Thrasymachus, proponent of the thesis that justice is the will of the powerful, as being refuted comprehensively by Socrates (see Plato §14). The refutation postulates a human capability to discern principles of right societal conduct independently of any formal enactment or legislative decision made by somebody with power. These principles in their very nature are normative, not descriptive. In Aristotle, the same general idea emerges in the form of noticing that whereas much that is observed as law is locally variable and arbitrary, there appear to be fundamental common principles across different polities. Some principles may then be legal simply ‘by enactment’, but others seem to be so ‘by nature’. Explorations of the nature of humans as rational and political animals may then help to underpin the idea of that which is right by nature, but that exploration is more the achievement of Aristotle’s successors in the Stoic tradition than of himself (see Stoicism §18). Roman jurists adapted some of the Stoic ideas of natural law in their expositions of the civil law, and subsequently, for medieval and early modern Europe, the existence of the Justinianic (see Justinian) compilation of the whole body of Roman law was held by many thinkers to embody in large measure the promise of law as ‘written reason’ (see Roman law; compare Gaius; Bartolus of Sassoferrato; Pothier, R.J.).

In any event, the greatest flowering of the Aristotelian idea came with its fusion into the Christian tradition in the work of Thomas Aquinas (§13), hugely influential as this has been in the developing of Catholic moral theology in the succeeding centuries. After at least a century of relative neglect among legal scholars, especially in the English-speaking world, the last quarter of the twentieth century has seen a strong revival of the Thomistic approach in the philosophy of law (see Natural law), with contemporary thinkers developing the idea of the basic goods implicit in human nature, and showing both how these can lead to the elaboration of moral principles, and then how positively enacted laws can be understood as concretizations of fundamental principles.

In the seventeenth century, other strands of essentially the same idea had led to the belief, for example, of Hugo Grotius, that basic principles of right conduct and hence of human rights are themselves ascertainable by intuition and reason (compare Pufendorf, S.; Stair, J.D.). Kant’s representation of the principles of practical reason is the classical restatement of this position in its most philosophically rigorous form (see Kant, I. §§9–11; Kantian ethics §1).

In a wide sense, all these approaches may be ascribed to rationalism, as contrasted with voluntarism (see Rationalism; Voluntarism). For they treat law, or its fundamental principles, as discoverable by rational and discursive means, independently of the intervention of any legislative will. They do not, of course, deny the need for legislative, or adjudicative or executive, will. Even if fundamental principles stand to reason, their detailed operationalization in actual societies requires processes of law-stating, law-applying and law-enforcement. But the issue is whether these are fundamentally answerable at the bar of reason and practical wisdom (prudentia), or not. To the extent that they are so answerable, we have a concept of some ‘higher law’, some law of reason, by which to justify, to measure and to criticize the actual practice of human legal institutions. If the rational derivation of this depends in some way on a teleological understanding of human nature and its relation to the creator and the rest of the created universe, we may reasonably enough call this a ‘law of nature’ or ‘natural law’.