Natural Law

Lewis points to the existence of a Natural Law, or a universal knowledge of right and wrong, as the first evidence that God exists. The supporting evidence for the Natural Law is all human civilizations, including the early forms of tribal societies, have similar codes of ethics which arise from the Natural Law. Thus, murdering each other is not ethical, but killing other humans is allowed for defense of the society from other societies. Stealing is not allowed, but trading is.

Along with this, Lewis observes that humans have a difficult time following Natural Law, and this point is as important as the existence of Natural Law. Humans are by nature imperfect. Lewis believes humans were created imperfect on purpose, in order that perfection might become their goal, if chosen through free will. The motivation for selecting perfection over remaining imperfect starts with the discomfort humans feel...