Natural Law is law which ‘authorises’ all positive, human laws. According to its classical exponents it is located in the purity of human reason, and, to its Christian theorists, in reason and conscience, motivated by an instinctive need to guarantee human survival. It is a form of knowledge which spurs us to follow virtue and shun vice. The concept dominated Renaissance thought and, through its literary equivalent, later to be called poetic justice, it influenced all English writers of the period in fundamental ways. There was a sceptical and resistant tradition dating from Calvin and summated by Hobbes, suggesting that after the Fall Natural Law existed, not, as Aquinas held, in the human mind and heart, but in God's will and the sovereign's fiat, but even this line of argument necessarily worked within the terms laid down by Aquinas.

Natural Law may be regarded simply as an intellectual ‘model’, since in the realm of observation it has ‘never really existed’. No actual society has ever been built upon its premises.