Lewis claims that he has now established a “foundation” for his argument: there is such a thing as a moral Law of Nature. In this chapter, he will strengthen this foundation by discussing moral law in more detail.
Lewis usually begins a chapter with a brief overview of the previous chapter or chapters, reflecting the fact that this book was originally delivered as a series of nightly radio broadcasts.
Some people might say that Moral Law is a kind of “herd instinct”—an intuition that has evolved over centuries, just like every other human instinct. To respond to this idea, Lewis imagines hearing a cry for help. If he were to hear such a cry, he’d feel three emotions—first, a desire to help; second, a desire to keep out of danger. But there would also be a third emotion—an intuition that the first emotion is “right” and the second emotion is “wrong.” So moral behavior may indeed be the product of instinct—but that doesn’t follow that morality itself is just instinct: that would be like saying that a sheet of music is the same thing as a piano key.
The idea that morality is a form of instinct became increasingly popular during the 19th and 20th centuries—many notable thinkers and philosophers, such as Friedrich Nietzsche, argued that ideas of right and wrong were just “human customs.” Lewis’s rejoinder to Nietzsche and other similar philosophers is that humans feel many different instincts at once—so there must be some overarching moral law telling us which instincts to obey and which ones to ignore.
Another rebuttal to the theory that morality is instinct: if morality were a form of instinct, then most of the time, the instinct for self-preservation would trump it. When we hear someone in danger calling out for help, our instincts to save ourselves from the danger are probably stronger than our instincts to save others—yet often, we choose to risk our lives to offer help.
Lewis argues that morality is often irrational—there seems to be no rational reason why humans would want to endanger their own lives to save other people. Therefore, it follows that morality cannot be a human invention—how could humans “invent” something so irrational and potentially dangerous as morality?
One final rebuttal: morality can’t just be a form of instinct, because there are no instincts that we consider to be moral one hundred percent of the time (e.g., some of the time, our instinct to love our mothers is moral; sometimes it isn’t). If morality were instinctive, then there probably would be some instinct that was always moral. By the same token, there is no such thing as a piano key that is right or wrong 100 percent of the time—sometimes a key can be right, and sometimes the same key can be wrong, according to the directions of the sheet of music. It’s worth emphasizing that no instinct is moral all the time. A lot of people build their entire lives around one specific instinct—to love one’s family, to protect one’s country, to have sex, etc. Such a life is deeply misguided, because people need morality to tell them when their instincts are good and when they’re not.
Lewis argues that if morality were a human invention, based on instinct, then morality would agree with human instinct (or at least one specific human instinct) one hundred percent of the time. The purpose of morality, in short, is to teach human beings when to obey their instincts, and when to ignore them. Notice that even in Book One, Lewis expresses his opposition to absolutism of (almost) all kinds—it’s morally wrong, he argues, to prioritize one’s family, one’s sex drive, or one’s country all the time. As we’ll see, the only form of absolute thinking that Lewis accepts is worship of God.
Another potential objection to the theory of moral law: moral law is just a social convention, something that we all learn from our schoolteachers. But just because we learn something from a schoolteacher doesn’t mean that it’s just a human convention—after all, two plus two equals four, whether we learn it in school or not. Strange though it might sound, moral law falls into the same category as a mathematical law: it’s a universal truth that transcends humanity.
Just because we learn morality in school doesn’t meant that morality isn’t also a universal truth. Lewis reiterates the idea that morality is a “law”—like mathematics, morality cannot be changed. Just as two plus two equals four no matter where or when you are, murder and theft are wrong and always will be wrong.
Lewis now asks us to consider in more detail the idea that all moralities are fundamentally the same. Clearly, people over time have had some different ideas about what it means to be a good person. But the very fact that people do disagree on this matter suggests that there really is a correct answer to the question of what it means to be good. Consider the history of witch-burnings in England. For centuries, women were murdered for the supposed crime of witchcraft. One might point to witch-burnings as evidence for how greatly morality has changed over time—and therefore, how arbitrary it can be. But remember that the witch-burners of the past believed that witches were real. If modern-day people believed that certain human beings made pacts with the devil, they’d probably burn those people, just as their ancestors did. There is, in short, no real difference between a modern person’s morality and a witch-burner’s morality—the difference is that modern people have more knowledge.
Some people would point to atrocities like the Spanish Inquisition or witch burnings and say that humans have no universal morality—how could the people who burned innocent women believe in the same morality (and even religious doctrine) as modern churchgoers? Lewis’s point is that witch-burners and modern Christians do believe in the same laws of right and wrong; they just have different information about the world. Put another way, witch burners didn’t burn innocent women because they were evil; they did so because they sincerely believed those women to be witches. Moral codes have changed very little over history, and basic moral law is exactly the same as it ever was (according to Lewis).