Aquinas believed there were four primary precepts, “God’s aims for humans”, which we are to follow to live according to natural law. These are to reproduce, learn and develop potential, live harmoniously in society and worship god. These precepts are moral absolutes and under no circumstances can be broken. Natural law is therefore a deontological theory. According to Aquinas natural law was the, “moral code which human beings are naturally inclined towards.” There are also the secondary precepts to take into account, which are the rules and regulations which help us achieve these aims. These are actually man made laws which are based on God’s principles.
Natural law is a fusion of the secular philosophy of Aristotle (who claimed that everything had a purpose and therefore the fulfilment of these purposes was good, e.g. a good knife cuts well) and the religious tradition of the church by Aquinas. Natural law was to be a supplement of the laws given in the scriptures and draws much inspiration from the bible. Paul in Romans 1-3 argues that the moral law of God is evident from the nature of humans and the world, “Ever since the creation of the world, his invisible nature, has been clearly perceived in the things that have been made.” (Romans 1:20) In Matthew 19:3-9, Jesus observes that natural law should make it clear that divorce is wrong, “For your hardness of heart Moses allowed you to divorce your wife, but from the beginning it was not so.” Marriage was designed for the building up of the married couple by each other and for birth and secure upbringing of children; divorce goes against God’s aim.
Peter Mullen, Working with Morality, states, “Reason and the regularities of the natural world should be your guide.” Though are ability to reason we can get a sense of right and wrong. We can think freely for ourselves and discover God’s intention and follow natural law. In other words we must use our reasoning powers in order to work out what is moral. This helps us deal with ethical issues which are not dealt with in the scripture e.g. euthanasia.
In his book, Summa Theologiae, Aquinas maintained that we have four cardinal virtues (‘cardo’ meaning ‘a hinge’) on which are morality hinges and these four things inform as reason as well as the Decalogue. It has also maintained that we have seven capital vices. The cardinal virtues are prudence, justice, fortitude and self control. Pursing what is morally right will help us to develop these virtues and vice versa. The seven sins of morality are just the vices of pride, avarice, lust, envy, gluttony, anger and sloth. Aquinas maintains that these, in contrast with the four virtues are totally opposed to achieving the goals set out for humans in natural law. These natural virtues are expanded by the revealed virtues of faith, hope and charity derived from St Paul in Corinthians and “Aquinas held that the greater the extent to which these are developed by the individual,...