Natural Law approach to morality has a long history. Cicero in De Re Publica describes natural law as follows:
True law is right reason in agreement with nature. It is applied universally and is unchanging and everlasting … there will be no different laws in Rome and in Athens, or different laws now and in the future, but one eternal and unchangeable law will be valid for all nations and all times, and there will be one master and ruler, that is God …
However, it was Aristotle who really developed this approach and Aquinas (1225–74) built on his thought. The writings of Aristotle had been lost in the West and preserved amongst the Islamic scholars of the East. They were reintroduced into Western thought shortly before Aquinas took up his position as a professor at the University of Paris.
Aquinas considered that natural law was the moral code which human beings are naturally inclined towards. God reveals specific commands but these do not go against natural law but rather further and develop it. This reflected Aquinas’ approach to theology generally by which natural theology (which was based on human reason) did not go against revealed theology (which was based on revelation by God). Aquinas said that the moral life is the life which is lived ‘according to reason’ and, indeed, acting in accordance with reason was the same as acting as a Christian would act. Aquinas’ main difference from natural law philosophers who did not believe in God was that he considered that human beings were immortal and any moral theory and understanding of natural law had, therefore, to take account of the belief that the purpose of human existence did not lie entirely in this life.
Aquinas argued that the first priority laid down by natural law was that the self had to be preserved not just in this life but beyond the grave. If the self gave in to non-rational desires, then it became enslaved. It was possible to arrive at the natural or cardinal virtues (prudence, temperance, fortitude and justice, taken from Aristotle) by the use of reason alone. The Ten Commandments (with the exception of the command to keep the Sabbath day holy) were held to be examples of natural virtues. These natural virtues are expanded by the revealed virtues (of faith, hope and charity – derived from St Paul, cf. 1 Corinthians 13:13) and Aquinas held that the greater the extent to which these are developed by the individual, the greater will be the obedience to natural law.
The starting point for all advocates of natural law is to work out the purpose of human life. For Aquinas, this purpose included to live, to reproduce, to learn, to have an ordered society and to worship God. Reason is used to find out God’s intention and the purpose of human existence and this will enable one to arrive at the principles of natural law.
Unlike Augustine and some of the later Christian reformers such as Calvin, Aquinas did not consider that human nature was totally corrupted. He considered that human nature, even though imperfect, was a reasonable guide to what human nature should be – since it was created by God. For Aquinas, there is no category of human beings that are in some way enslaved by a depraved nature – there is an equality of all human beings and in all human beings there is a necessary link between their happiness and their virtuous behaviour. Aquinas therefore starts from his experience of people and he expects to find natural law at work in every society in the world since all societies are made up of human beings who share a common nature. Natural law can be deduced from an examination of human nature and the ends for which human beings are created.
When we term God as good from our human perspective, Aquinas maintained that we name him as the goal of all desires or that to which all desires tend. Natural law can show all human beings what is good – religion is not needed for this and this is similar to St Paul’s claim that the law is written in the hearts of all men (Romans 2:14ff). Reason can bring people to act rationally to develop the virtues. For Aquinas, ‘God is good’ is analytic in that it expresses a truth about God (that God is fully whatever it is to be God), but it is also synthetic as God represents the goal and destiny of all human beings, even though human beings may not recognise this. Aquinas based this idea on ‘fitness for purpose’ – since he held that humans were made by God for fellowship with God it follows that God, as their creator, must be the means by which human happiness will be found. Aquinas did not consider that morality was based on commands from God – a position which William of Ockham held as he considered that morality was based on revelation – Ockham held that if God commanded adultery then this would be right because of the command. Aquinas considered that if this was the case then God’s commands could be irrational and arbitrary. Instead God makes human beings with a certain nature and this nature enables human beings to use their reason and their experience to understand what is right.
Aquinas considered, following Aristotle, that all men will the good. Human beings may seek some apparent good, but this is not a true good – it is only an apparent good because it does not conform to the perfection of the human nature which all human beings share. Aquinas considered that there is an ‘ideal’ human nature which we all have the potential to live up to or to fall away from and our moral actions are crucial in determining where we stand in this respect. If a person does something that is morally wrong, he or she will do this because they consider this to be a good although the possibility of the individual being mistaken certainly exists (examples might include smoking, drinking too much or even taking drugs). Aquinas says that: ‘A fornicator seeks a pleasure which involves him in moral guilt’ (Summa Theologica 1a, 19, 9). The fornicator seeks a pleasure which he thinks is a good, but this is only an apparent good as it diminishes a human being’s nature.
Sin, for Aquinas, involves a falling short from the good – it means a human being becoming less than he or she is intended by God for him or her to be. To pursue an apparent good rather than the real good is to fall short of our real potential – it is to ‘get it wrong’ and to be mistaken. No one seeks evil for itself, it is only sought as an apparent good and therefore rests on a mistake. Hitler and Stalin did not seek to do evil – they sought what they thought were goods but they were mistaken – they strove for apparent rather than real goods. Sin is a theological word but there is no real difference between this theological idea and acting against reason. Aquinas says: ‘the theologian considers sin principally as an offence against God, whereas the moral philosopher considers it as being contrary to reason’ (S. T. 1a, 11ae, 71, 6, ad 5).
Since Aquinas argued that it is possible to be mistaken in which goods are chosen, it is obviously necessary to determine what is the right thing for a person to aim for. In essence, this is what discussion of natural law is about – seeking to explore what is the right good to aim for. Human beings have the ability, using their will and reason, to make deliberate moral choices (S. T. 1a, 11ae, 1, 1) which Aquinas terms ‘human acts’ to distinguish them from those acts performed by a person which are based on instinct. However, human reason must be used correctly, which leads Aquinas to talk of the ‘right use of reason’ – reason may be used to plan a murder or to decide to be virtuous, but only in the second case is reason being used ‘rightly’. This obviously raises the problem of how one determines what is the ‘right’ use of reason when there are genuine differences of opinion as to what is good in a particular situation. A person’s reason and their will both work together to help determine the choice they will make – if a person uses their reason correctly to determine what is right and then wills to do it this is, according to Aquinas, a free choice.
A person may will to make a morally wrong choice which he or she does not carry through – perhaps because the choice is not available. A man may, for instance, decide to defraud his employer of a substantial sum of money but he never gets the chance because he is moved to a new job.
Aquinas distinguished ‘interior acts’ and ‘exterior acts’ and is clear that the former are the most important – indeed morally good or bad acts are generally interior acts. An act may be good in itself but done for a wrong intention – for instance giving to charity may be good in itself but if it is done in order to attract praise then there is a bad intention (‘for instance, we say that to give alms for the sake of vainglory is bad’ (S.T., 1a, 11ae, 20, 1)). This does not entail that intention alone is decisive. As Copleston says in his book Thomas Aquinas:
As Aquinas says, there are some things which cannot be justified by any alleged good intention … If I steal money from a man in order to give it to someone else, my action is not justified by my good