Natural Law includes those ethical theories which state that there is a natural order to our world that should be followed. This natural order is determined by some supernatural power. Natural Law as we understand it originated in the philosophy of the ancient Greeks, especially that of Aristotle, and was developed by Thomas Aquinas. It is an absolute theory of ethics but it is rooted not in duty, or in an externally imposed law, but in our human nature and our search for genuine happiness and fulfilment. Aquinas considered that by using our reason to reflect on our human nature, we could discover our specific end (telos) or purpose and, having discovered this, we could then work out how to achieve it. This understanding of God’s plan for us, built into our nature at creation, Aquinas called Natural Law.