Natural Moral Law

Natural moral law (NML) is a deontological (duty-based) ethical theory rooted in the idea that there is an objective moral order built into the nature of human beings and the universe. The theory's most influential formulation comes from St Thomas Aquinas (1225–1274), who synthesised Aristotelian philosophy with Christian theology. Aquinas argued that God has designed human nature with a specific purpose (telos), and that by using reason to reflect on this purpose, humans can discover universal moral principles.

Key Definition: Natural moral law is an absolute, deontological theory that holds that morality is grounded in human nature and can be discovered through reason. Actions are morally right if they fulfil the natural purposes (telos) of human life as designed by God.

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Aristotle's Telos

Aquinas drew on the Greek philosopher Aristotle (384–322 BCE), who argued that everything in nature has a telos — a purpose or goal towards which it naturally tends. For Aristotle, the telos of a human being is eudaimonia (flourishing or happiness), achieved through the exercise of reason and virtue.