Since the time of Aquinas most moral philosophers who have engaged in describing natural moral law as a normative system of ethics have agreed with this basic structure. Some have developed slightly different interpretations of the primary precepts, which in turn may give slightly different secondary precepts, but there has been a general consensus. This consensus has had the effect of making the focus of discussions of natural moral law the detail of how it should be applied; it has become very legalistic. This may not be particularly helpful or even true to Aquinas. Aquinas followed Aristotle in arguing that ordinary people through ordinary reason have the power to understand the difference between right and wrong; the more complex a system is developed out of natural law, the less it can serve as a basic and universal system for determining values.
Today, ethicists who use the natural law approach differ in their interpretation of:
1. What the universal human nature (formal cause) and purpose (final cause) is. They each have slightly different lists of primary precepts, sometimes called "basic goods". For example:
a. Germain Grisez (1983): self-integration, practical reasonableness, authenticity, justice and friendship, religion, life and health, knowledge of truth, appreciation of beauty, playful activities
b. John Finnis (1980): life, knowledge, aesthetic appreciation, play, friendship, practical reasonableness, religion – introduced ‘the marital good’ in 1996
c. Timothy Chappell (1995), pictured below: friendship, aesthetic value, pleasure and avoidance of pain, physical and mental health and harmony, reason, reasonableness and rationality, truth and knowledge of it, the natural world, people, fairness, achievements
2. How we should deal with a situation where an action seems to contribute to one but takes away from another of the primary precepts or basic goods? Most scholars operate a "master rule" approach, holding that there is a single essential principle which underpins all the others and takes priority or that one of the primary precepts takes priority in a dispute.
a. Aquinas, for example, held that the primary precepts could be summarised in the Christian Golden rule (do unto others as you would have them do unto you)– in other words – always want to do what is right and consider the impact on everybody else before acting, trying to act in everybody’s best interests, not just selfishly.
b. Grisez suggested that the "first principle of morality is voluntarily acting for human goods and avoiding what is opposed to them, one ought to choose and otherwise will those possibilities whose willing is compatible with a will towards integral human fulfilment."
c. Finnis now affirms Grisez’s master-rule approach, though in the 1980s he felt that any "master rule" approach was likely to suffer from not being able to answer the simple question "Who says this is the master rule?" satisfactorily. In the past Finnis argued that all basic goods are known through practical reason (i.e. experience and common sense) equal and that it would always be wrong to intend the destruction of an instance of a basic good i.e. no lying as knowledge is one of his basic goods, no murder as life is a basic good etc. If there really is a clash that can’t be reasonably worked out, there is something wrong with our list of basic goods, our interpretation of experience.
Some natural law theorists adopt a "virtue" approach however – and argue that we should focus less on specific actions and precepts and more on the character traits which will help us to achieve our ultimate fulfilment, individually and as a people. Virtue ethicists who develop the natural law approach include Alasdair MacIntyre and Philippa Foot.
These days Timothy Chappell is sceptical about the value of any systematic moral theory, whether Kantian, consequentialist, contractualist, virtue-ethical, or natural-law-based. Like Alasdair MacIntyre he sees systematic moral theory as a manifestation of an inhumane scientism and (bad-sense) scholasticism whose main features are reductively determined by the sociology of modern university life. Like Iris Murdoch and Simone Weil, he sees moral imagination as a key ethical resource, and one that unfortunately is generally better understood and deployed by artists than by philosophers. Like Bernard Williams, he thinks that a livable and authentic ethics can only emerge from moral phenomenology – from honest reflection on what we actually know in moral experience. Like Emmanuel Levinas, Martin Buber, and Stephen Darwall, he takes second-personal encounter to be fundamental to this sort of moral phenomenology. And like Charles Taylor, Hegel, Nietzsche and Aquinas, he thinks that there can be no adequate understanding of our own moral thought that is not acutely conscious of its own contingent history.
Most of those who follow a new natural law approach also adopt a paradigmatic approach, i.e. they accept a single explanation for why the world is the way that it is. The most common paradigm for a natural law ethicist to belong to is the religious paradigm: God created the world and everything in it and wills us to fulfil his plan. Aquinas is one example of a religious paradigmatic approach to natural law, Grisez is another. There are those who adopt a non-religious paradigm or explanation for things being the way that they are. Evolution and natural selection may be one paradigm which would enable a non-believer to follow natural law. The American legal and moral philosopher Ronald Dworkin, for example, is a non-religious natural law theorist. In his 1994 book Life's dominion: an argument about abortion, euthanasia and individual freedom he argues that abortion and euthanasia are consistent with respect for the good of life.
However, other scholars are non-paradigmatic in their approach i.e. they don’t explain why things are the way they are; they just accept it and argue that it seems common-sense. Aristotle was such.
Most followers of natural law ethics accept that:
a. Human reason is a reliable tool for determining what the final cause of human beings and other beings/things is.
b. When people choose to do bad things it is usually because they are pursuing an apparent good – i.e. they think it will be better for them if they murder, lie, steal etc. it will contribute towards the good of their continued peaceful life, their prosperity maybe. If they reconsidered they would realise that they are being mislead and would instead choose the real good of not murdering, stealing or lying as the general flourishing of mankind is the condition upon which individual flourishing rests.
c. We should try to act with a good motive as well as to produce good results – this because the motive comes out of and informs the character and a character can be made un-virtuous if it allows itself to act from poor motives, even if the general results are not bad. This is what Aquinas called the importance of interior as well as exterior acts.
New natural law is used as the basis for a philosophy of law as well as normative ethics by some scholars. Some see the civil law as valid or invalid in terms of whether it reflects universal natural laws of mankind. Cicero wrote: “True law is right reason is agreement with nature; it is of universal application, unchanging and everlasting. It summons to duty by its commands and averts from wrongdoing by its prohibitions.” Aquinas believed that what is morally and what is legally right ought to be the same thing. Blackstone argued the same. Thus they are both followers of what is known as the overlap thesis, most famously expressed by Augustine, who wrote that “an unjust law is not really a law at all”. They are also called conceptual naturalists.
Other scholars, conceptual non-naturalists, argue against this and suggest that what is morally right and wrong has little to do with the law, which reflects pragmatism and short-term particular political ends and is justified either by democratic mandate or the power of the government to enforce it. The utilitarian John Austin wrote: “Now, to say that human laws which conflict with the divine law are not binding, that is to say, are not laws, is to talk stark nonsense. The most pernicious laws, and therefore those which are most opposed to the will of God, have been and are continually enforced as laws by judicial tribunals”(1995). Brian Bix (1999) has argued against Austin and others who reject the overlap thesis by saying that Austin’s criticism implies that we may as well accept that any law that can be enforced by a court is just – something which even Austin would dispute, as would most sensible people.
John Finnis (1980) and Brian Bix (1996) attempted to show that this is a non-dispute, however, by pointing out the difference between claiming that a law has no status in theory and arguing that it does not exist in practice.
John Finnis is a neo-naturalist or founder/follower of new natural law and sees himself developing the conceptual naturalism of Aquinas and Blackstone. He sees both of them as providing an argument which would enable people to see that following the law is morally right and that the law has the moral authority to coerce people (i.e. use prison and even death as a punishment). Ronald Dworkin agrees on this point. Finnis claims that a law can be legally valid, even if unjust, but that there can be no moral justification for enforcing an unjust law.
Finnis’ neo-naturalism is both an ethical theory and a theory of jurisprudence. Human beings share a common nature and purpose, which are fulfilled by the pursuit of common basic goods. The function of moral and civil rules is to enable the pursuit of basic goods and thus contribute to the flourishing of the human race. “The conceptual point of law is to facilitate the common good by providing authoritative rules that solve the coordination problems that arise in connection with the common pursuit of these basic goods.”