Start here: Natural Law Theory

In its classical Greek form, Natural Law is the opposite of moral relativism – the view that values come from culture. Aquinas believed morality was a function of the rational human nature that God has given us, and stressed that God’s purposes in Creation defined our purpose as human beings, and therefore how we ought to lead our lives.  Values come from our nature and the natural order, not from our culture.

Classical Natural Law Theory

In ancient Greece, relativists questioned the weight of the moral law. Moral laws, they suggested, as they vary from nation to nation, must be seen a positive laws, laws passed by parliaments. As such they are just products of society, conventions, and so some of them thought, are not really binding.

This was opposed by Plato and Aristotle and Cicero. Morality is not conventional, these thinkers argued, but natural. There is a natural law that must be obeyed whether it is written down by law-makers or not. This is a theory of moral objectivism – the belief that morality exists independent of human law or perception.

Greek philosophers such as Aristotle  operated within a teleological worldview. Everything, says Aristotle has some end or telos and the good is that which people pursue as an ultimate end. It is our final causes or ends which define what is good for us, and ultimately our common aim is to flourish (Greek eudaimonia translates as happiness or flourishing).

At first glance this seems like a circular argument: what is the good? The good is what people pursue.  What do people pursue?  People pursue the good. Notice also that the good is observable in the natural world, and hence this theory does not depend on God, even though to Aquinas God is both the source and the end of human reason.

As relativism was associated with the idea that moral laws vary between societies, does this mean the natural law is unchangeable?

All that is necessary for a theory to be a natural law theory is that it oppose relativism, and holds that the moral law is independent of any human law. There is no reason, however, why such a moral law must be unchangeable, and so there is no necessary connection between natural law theory and the view that morality is immutable or absolute.

Thomist Natural Law Theory

Aquinas (adjective – Thomist) was originally denounced as a heretic by the Church, but then his natural law became the semi-official moral theory of the Catholic Church – discussed extensively in encyclicals.

When Aquinas adapted Aristotle in the thirteenth century he was seeking to reconcile Aristotle’s thought with Biblical revelation after Aristotle’s writing was rediscovered at the fall of Toledo to Christians in 1085, where the Islamic world had preserved his thinking in their libraries. See the introductory handout and powerpoint on this site. Aquinas saw natural law theory as a theory about the relationship between morality and human nature, the theory that who we are determines how we ought to act. There is way of living that is in line with our rational human nature and morality prescribes that we live such a life.

Aquinas understood human nature to be defined by reason and freedom; it is our ability to reason and to make our own free choices that sets us apart from animals. Whereas material objects and animals without free will do by nature, deterministically, as God wills them to do, we who have free will may choose either to play our part in God’s plan or not. Reason can tell us what this part is; our purpose is discoverable. With freedom comes responsibility to do as we were made to do.

However, Natural Law is usually described as deontological (deontos is Greek for duty) because it ends up with a set of rules such as “abortion is wrong”.  The influence of Aquinas on Catholic moral thinking is profound, as you can see by reading the Catholic Catechism (Catechism means “body of teaching”) on this site, or the Papal Encyclicals (something sent round from the deliberations of the College of Cardinals), which you also find here: Personae Vitae and Humanae Vitae.   It is better to see natural law as a deontological theory arising from a teleological worldview.

Criticisms

It is a traditional weakness of natural law theories that they are unclear in their application. It may be that the moral law is independent of any human law, but then how are we to know what it requires of us? It may be that there are fundamental principles of action then are evident to reason, but which specific acts do they prescribe in my circumstances?

People also criticise Natural law theories for implying that the good can be observed, without realising that all observation is culturally-conditioned, and by implying that what is thought to be natural is automatically good.  For example, it has been argued that the natural place for women is in the home bringing up children, so that anything that stops them doing this (eg a career) is wrong, or that one race is naturally less intelligent than another, so that slavery for example is justified.  We tend now to reject these views, by arguing that the natural differences between men and women are not morally relevant (nor are differences between races) and in so doing we say “natural law can produce very unjust outcomes” (such as the sexual and racial discrimination).

Can Natural Law be rehabilitated?  John Finnis is a modern natural law theorist who argues it can, even in an age dominated by utilitarian ethics.