Of all post-Enlightenment social sciences, economics might be easily classified as having the least in common with natural law theory. To the extent, for example, that economics is concerned with matters such as utility maximisation, cost–benefit analysis or identifying unintended consequences of particular decisions, its goals differ from natural law theory’s central focus on individuals and communities (including the state) knowing and choosing the good through right reason. Typically, what is called ‘positive economics’ – famously defined by the British economist Lionel Robbins as ‘the science which studies human behaviour as a relationship between ends and scarce means which have alternative uses’ (Robbins 1952: 16) – brackets off the type of normative questions with which natural law theory is concerned.

Those engaged in natural law reflection have, however, always brought their methods of reasoning to bear upon questions with significant economic components.

Not every creature has reason to live so as to fulfil its purpose in life. Just ask a battery hen. Her purpose in life is to produce as many eggs at as little cost as possible, then be turned into a raw material of the fast-food industry. The resultant misery and distress to the hen is just a corollary of her living according to her purpose, her telos – as a frank egg-farmer might admit. From the battery hen’s own point of view, there is no reason at all for her to live this way. As she would see it (if she had a chance to consider the question), she would be better off doing almost anything other than fulfilling her telos. Her telos and her flourishing are not the same thing. Almost all of the time, they do not even coincide.

The New Natural Law (NNL) theory is the name given to a particular revival and development of Thomistic natural law theory, first proposed in the 1960s by Germain Grisez in an interpretative article on St Thomas Aquinas, in which Grisez challenged the then-dominant interpretation of Aquinas on natural law. In subsequent decades Grisez, John Finnis, Joseph Boyle and others richly developed the theory and applied it to other issues (free choice, moral absolutes, abortion, euthanasia, marriage and others).

According to the interpretation of Aquinas’ natural law theory standard in the 1960s, the basic moral criterion is human nature itself. Actions are morally permissible if they conform to the teleologies inscribed within human nature, morally wrong if not. Since the standard for what is morally right is what fulfils human nature, one must first determine by a theoretical procedure what end or ends fulfil human nature.

The natural law conception of ethics is more closely associated with Thomas Aquinas than with any other thinker, and Aquinas’ position is famously grounded in a metaphysics of Aristotelian essentialism and teleology. It is often claimed that this metaphysics was decisively undermined by the scientific revolution. Hence it might appear that modern science has refuted what has been, historically, the main approach to understanding natural law.

Alternative versions of natural law may seem to sidestep this difficulty by looking for foundations in something other than an essentialist and teleological conception of nature. For example, Locke’s theory of natural law is grounded in the thesis of divine ownership of human beings. Violating the rights to life, liberty and property that we have under natural law is, for Locke, essentially a matter of damaging God’s property.

Any attempt to offer an account of natural law in Stoicism is confronted with the notorious problem of evidence. Not a single work of the ‘early’ Stoics (Zeno of Citium, Cleanthes and Chrysippus, all working in the third century BCE) has fully survived from antiquity. Reconstructions of their views depend on reports by authors who wrote much later and are in many cases anything but unbiased. The information that these authors provide usually leaves a rather wide scope for different interpretations. And the decision between these interpretations is often a matter of the general assumptions which guide our approach to the Stoics: whether we tend to think, for instance, that the early Stoics stood on common ground with their predecessors and contemporaries or whether we assume that they tried to distinguish themselves from other philosophers. As we shall see, this alternative is particularly relevant in the case of the natural law.

By acknowledging the place of reason in bioethics, natural law theory promises an ethics of life and death which, whilst acknowledging the social significance of consensus, consequences, cultural practices and competing religious precepts, offers a school of thought not reducible to these shifting, arbitrary and contradictory criteria. Advances in technology suggest that natural law theory can assist in the conduct of bioethics, if only because the natural law tradition entertains the possibility of universality, reason, objectivity and right answers in the realm of bioethics.

There are schools of thought that regard the death penalty a sound punishment for a change of religion or causing religious offence. In thirteen countries such legislation is recognised as binding and enforceable. These mandates are also seen by millions, both clerics and faith communities alike, as enforceable outside the jurisdictions that enact them.

The account of the natural law given by Thomas Aquinas has two claims to the title ‘natural’. First, the basic precepts of the natural law are naturally known, that is, they are accessible to us by the nature of our human minds. Second, the human good depends upon our nature. Philosophical inquiry, for instance, is part of the human good because of the nature of our minds. If we had the minds of squirrels, then philosophical inquiry would be alien to the human good.

For Aquinas, these two aspects of the natural law are intimately linked by way of natural inclinations. To possess a true nature – and not merely some abstract mathematical ‘nature’ – is to move towards certain ends. This natural movement or impetus Aquinas calls a ‘natural inclination’, not to be confused with an inborn desire.

This chapter investigates the problem of how the transplant and borrowing of foreign constitutional law and international law can influence constitution-making processes and constitutional interpretation – state actions which are still considered sovereign. International law, especially international human rights laws, are of pre-eminent importance in this context since they are virtually by definition based on limitations on national constitutional law to assert internationally shared constitutional principles. In other words, the chapter seeks to answer the question of how far the process of the internationalization of (national) constitutional law has progressed; to what extent are the framers of constitutions and the courts that interpret constitutions willing to accept alien, foreign, or international principles and rules? What underlies the decision by the constitutional organs of certain states to accede to such constitutional migration, and the rejection of such migration by their respective counterparts in other countries?

This chapter addresses the issue of democracy, in the context of this book on comparative constitutional law. It is readily apparent that the topic could be addressed from very different perspectives. Thus, the entire chapter could be directed towards differences between democratic and non-democratic constitutions. It might, alternatively, consider differences between constitutions within democratic polities, examining whether there are, or should be, constitutional differences that flow from different forms of democracy, or how far such differences result from the elevation of socio-economic norms to constitutional status. The chapter might have a different, more empirical, emphasis, with discussion as to the relative importance of constitutions in different countries. These are all significant issues, and each would occupy the entire chapter. They are not, however, addressed here.