Mere Christianity | Study Guide

C.S. Lewis

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Mere Christianity | Book 1, Chapter 3 : Right and Wrong as a Clue to the Meaning of the Universe (The Reality of the Law) | Summary



Lewis investigates the "odd" fact of our awareness of the Law of Human Nature and our failure to follow it.

A "bad" person is breaking the law of Human Nature, but a "bad tree" is not. When we call a tree "bad," we do not think it ought to have been different but are merely commenting on its unsuitability for our own designs. The "bad" tree obeys the laws of biology as does the "good" tree. And so Lewis says these natural laws are not really laws but only factual descriptions of what always happens. The Law of Human Nature stands apart as the one law that deals not with facts but with what "ought" to happen.

Our moral judgment cannot be correlated with self-interest. We consider a deliberate attempt to do harm to be wrong, but not harm done unintentionally. Conversely, a nation may employ traitors as spies while holding them in moral contempt.

Nor can the Law be explained in terms of society's claims upon individuals. There is no reason why an individual should care about society except for his desire to do what is right by being unselfish. This sense that one "ought" to do what is right, therefore, remains unexplained.

Lewis sums up his argument: the Law of Human Nature is not like the other laws in nature that describe what always happens under specific circumstances, like an apple falling to Earth due to gravity. We can choose to follow the Law of Human Nature. Nonetheless that Law is essential to who we are, and it has nothing to do with self-interest. Lewis concludes that the Law is a real thing that influences humans but was not made by them. In conclusion Lewis writes that "it begins to look as if we shall have to admit that there is more than one kind of reality."


In Chapter 2 Lewis refuted the ideas that the Moral Law was an instinct or a learned social convention. In this chapter he makes a distinction between the Moral Law and certain aspects of human psychology, such as self-interest and the desire to serve others. The Moral Law, Lewis insists, is something else that can neither be correlated with nor explained by these psychological features.

Lewis claims there is a fundamental difference between the Law of Human Nature and the laws that supposedly govern the physical world. We have no proof that something like gravity is a law in the sense of being a principle that governs the behavior of entities. Since science can only make assertions based on externally observable facts, we cannot know whether gravity is anything more than a description of what happens repeatedly. In contrast the Moral Law is what Lewis calls a "real law": a governing principle hardwired into us.

With this distinction, Lewis stakes out his position in a long-running and contentious philosophical debate. In the language of philosophy, Lewis's position would be described as "natural law moral theory." It holds that there is an objective moral standard arising out of human nature. Philosophy refers to scientific laws, like gravity, as "laws of nature." Necessitarian Theory regards these "laws of nature" or scientific laws as what Lewis would call "real laws": principles that govern behavior. In his view of scientific laws, Lewis agrees with the opposing Regulatory Theory, which views scientific laws or "laws of nature" as descriptions of repeated happenstance, not principles nature is compelled to obey. This subtle distinction has profound implications. Regulatory Theory concludes that the universe is a stack of contingencies, with no governing principle other than chance. Necessitarian Theory, on the other hand, claims the impossibility of this universe arising from random coincidence. It concludes there must be a reason why things are as they are—a governing principle, plan, or design behind it all. Lewis comes to the same conclusion as the Necessitarians, but he reaches it by means of the Law of Human Nature, not scientific laws.

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