Natural Law is an example of a deontological, absolutist ethical theory. Its origins can be traced back to Greek philosophy, specifically that of Aristotle and the Stoics. Aristotle was concerned with the telos or purpose of human existence and thought that it was to achieve eudaimonia – a state of human flourishing or happiness in which an attempt is made to develop the various personal qualities that nowadays cause us to describe someone as ‘well-rounded’. For the Stoics, the optimum life was one lived in accordance with our natural inclinations.
In its theistic form, Thomas Aquinas is most famously associated with this theory. According to Aquinas the fact that we are made in the image of God means that we are all invested with what he called the synderesis principle, an essentially rational and God-given ability to seek good and avoid evil. In addition to the Bible, Aquinas thought that God’s telos for us is revealed through using synderesis to identify and act on our natural inclinations.
These inclinations have been famously stated in the form of what are known as the Primary Precepts: heterosexual reproduction, the preservation of life, the desire to educate our young and to live in a community, and to worship God. In moral decision-making, we combine our rationality with these precepts, to produce secondary precepts: maxims that are specific to the situation at hand that we should then act upon.
For example, from the fact that we are inclined to reproduce heterosexually, secondary precepts can be generated that oppose the use of artificial forms of contraception and homosexual activity. The inclination to educate our young and live in a community might lead to the formulation of secondary precepts that oppose the use of child labour in sweatshops, or that might prompt an employee of a company that is illegally polluting the local environment to blow the whistle on this activity. The poor health conditions in sweatshops put people’s lives at risk, which again might lead to an act of whistle-blowing. If an employer forces us to work on the Sabbath this may also make us ponder whether we should change employers in the interest of worshipping God.
Aquinas recognised that we can rationally pursue apparent good rather than real ones (because of our fallen condition). So a pupil who takes a break from stressful revision to party all night might think this is sensibly justified at the time that they make this decision but regret it later when they are too tired to take in vital information the next day.
Ultimately, Aquinas thought that out telos was to achieve union with God. Living in accordance with the precepts while we are here on earth is one way to ensure that.