It is not uncommon to find the term ‘natural law’ being applied to any philosophical theory that espouses a belief in the ‘objectivity’ of moral standards, or the possibility of moral knowledge. If we avoid this inflated usage, however, and seek to identify a natural law tradition that is to some extent distinct from other cognitivist moral theories, it is probably best to identify such a tradition in terms of three basic features. First, natural law theories regard morality as, in some sense, a body of precepts. Even if the theory has a broadly teleological character, it will not have a nakedly maximizing structure: rather, the teleology will serve to justify a body of rules or standards. Secondly, natural law theories take juridical equality as a fundamental assumption: men are assumed to be of equal standing before the law of nature. Even when the theory serves to justify unequal rights in the real circumstances of society, those unequal rights are justified by reference to principles that treat everyone equally. The tension between natural rights and positively established rights which is therefore implicit in the idea of juridical equality finds expression in the third basic feature of natural law theories: the way in which they approach the relationship between natural law and the positive law enacted by men. Natural law represents the ultimate objective foundation by reference to which positive laws must be evaluated. But positive law is nevertheless necessary, and is far more than just an imperfect reflection of natural law. Positive laws are required in part to induce compliance with standards that would not otherwise receive the obedience of weak or evil men; but they are required also to give concrete detail to the general requirements of natural law. Natural law may require, for example, that conduct in certain areas of social life should be co-ordinated, but it will not necessarily specify the precise form that that co-ordination should take: natural law therefore requires the existence of positive law as a body of publicly ascertainable rules making co-ordination possible.

Perhaps the most significant metamorphosis of the natural law tradition is to be found in the shift from the position of Aquinas, which achieved pre-eminence in the later Middle Ages, to the theories of Grotius and Pufendorf in the 17th century. Most commentators have been struck by the change in character that natural law theory undergoes over this period, but there has been less agreement about what features actually mark the essential difference. On one view, the 17th-century writers put forward a theory of natural rights rather than a theory of natural law. But, although the 17th-century theories certainly display a more individualistic character, this is not invariably associated with the development of a rights-based theory: Pufendorf, for example, takes ‘duty’ as his basic concept rather than ‘right’. On another view, the 17th-century writers offer a secular theory which can be contrasted with the theo-centric approach of Aquinas. For reasons that will be explained, this view must be rejected. A better way of comprehending the change of tone and approach that separates Aquinas from Grotius is by reference to the role that notions of ‘good’ play in their theories. For Aquinas, an account of what is good for man forms the central pillar around which an understanding of natural law must be constructed. The role of positive law is to provide for the good, thus considered. For Grotius and Pufendorf, on the other hand, the role of law is to provide a framework within which men who are self-seeking and who live in conditions of scarcity may live together in a social order that enables each to pursue his own good as he conceives it. Although it would clearly be absurd to portray writers such as Grotius and Pufendorf in the guise of fully fledged liberals making a dramatic break with the past, it is nevertheless some such change of emphasis and orientation that marks the distinctive character of the theories that emerged in this period.

Given the way in which natural law theories depend upon some deep notion of human equality, and yet frequently adopt a conservative standpoint towards the material inequalities of social life, various stratagems have been adopted in order to bridge the gap between ideal and reality. Thus, in 17th-century thought, a basic right to appropriate and enjoy the resources of the natural world is possessed by men equally, yet it serves to justify the unequal division of wealth and resources in established society. In Aquinas the tension appears and is resolved in a different form, within his central notion of the good. The Aristotelian view, that the best life for man is a life of philosophic contemplation accessible only to a leisured elite, is replaced in Aquinas by the idea that man’s ultimate good lies in a beatific vision of God that is potentially accessible to everyone, but only in a life after death: the postulate of equality is preserved by moving its centre of gravity to another world. It is in this recurring tension between the ideal realm of equality and the material world of inequality that we find the basis for Marxist critiques of natural law theory and, indeed, of bourgeois legal thought more generally.

The orthodox position for the natural lawyers of the 17th century was that the content of natural law could be determined by reason, but that it derived its binding force from the divine will. The role of the notion of divine will within such theories was, in effect, to preserve a deontological character for natural law within a basically teleological form of argument. According to both Grotius and Pufendorf, reason shows us that human nature and circumstances being what they are, man can live in society only if certain basic rules are observed, e.g. rules defining and protecting rights of property. But this establishes only that such rules are requirements of utility: it does not show that they are requirements of natural law. Thus Pufendorf is careful to point out that, considered apart from the divine will, the precepts of natural law are merely ‘like the prescriptions of physicians for the regimen of health’ but are not laws (De Officio Hominis et Civis, 1682, 1.3.10). Actions are right and wrong (as opposed to wise and foolish) only in relation to a law: and a law, Pufendorf holds, presupposes the will of a superior. Natural law binds by virtue of the divine will. Given that we know certain rules to be necessary for social life, we know that such rules must be willed by God. Since God created our nature and fitted us with the capacities that make social life possible, it must be his will that we should live in society and observe those rules that are necessary for the existence of social life.

Grotius is often regarded as denying the role of the divine will in natural law, and he was so interpreted by Pufendorf, who attacked him on precisely this point. It is in fact unlikely that Grotius intended any such radical move away from the theo-centric approach. He says that natural law arguments would have a degree of validity even if God did not exist: but this may simply mean that the rules of natural law are not arbitrary but are founded on the nature of man and of his circumstances. In fact the idea of the divine will could not be so easily discarded, since it was employed in these theories to solve a number of fundamental problems. First was the question of how an action being obligatory differs from an action being one that we merely have good reason to perform. Second was the question of how moral reasons are related to prudential reasons: a problem that became particularly acute once morality was conceived of as a body of rules rather than as based on certain virtues as aspects of character. Lastly, and most significantly for our purposes, the notion of the divine will preserved a deontological character for natural law even while the reasoned arguments being offered were arguments of a basically utilitarian character. As we shall see, it was this feature of natural law thought that was later to bring about a dramatic transformation that some have seen as the death of natural law.

It might at first be thought that Hobbes represents an exception to the argument that 17th-century natural law theories ascribed a vital role to the divine will. There are of course large questions about whether Hobbes forms part of the natural law tradition at all. But it should be noted that, on the concept of natural law, Hobbes puts forward the orthodox view that precepts of reason can only be thought of as laws if they are considered to be products of the divine will (see ch. 15 of Leviathan, 1651).

As we have seen, the theo-centric framework of natural law theory preserved a deontological form for the precepts of natural law while allowing the substantive arguments (the need for certain rules given the known features of human nature, etc.) to take on a basically utilitarian character. What is often described as the ‘critique’ of natural law produced by David Hume in the 18th century is really best understood as a removal of the deontological framework, leaving only the utilitarian arguments in place. Hume removed God from the picture and offered a justification for rules of justice and property that appealed straightforwardly to arguments of ‘convenience’ or utility. Once this move was made, however, a dramatic sea-change was in process, for if the rules of justice and property are not prescribed by God, they are simply justified by utility. Of course, when Hume spoke of utility he did not have in mind a simple maximizing structure with a clearly defined maximand. But in the hands of Bentham, the notion of utility was developed in precisely that way.

Hume’s removal of God from the picture of natural law was undoubtedly a decisive move. Yet the underlying utilitarian cast of much natural law writing meant that there was a good deal of continuity between Hume’s predecessors and his immediate heirs. There had always been a tendency for the separate precepts of natural law to collapse into a general injunction to maximize utility, so that natural law ideas could continue to live a ghostly afterlife in the writings of utilitarians. Moreover, the reliance on speculative histories of, for example, the rise of private property, which had characterized the writings of Grotius and Pufendorf, was to take on a more descriptive and naturalistic character in the work of Adam Smith and the writers of the Scottish Enlightenment.

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