Morality is both a universal and a surprising fact about human nature. When I say that morality is universal I am not referring to this or that moral code. In fact, I am not referring to an external moral code at all. Rather, I am referring to morality as the voice within, the interior source that Adam Smith called the “impartial spectator.” Morality in this sense is an uncoercive but authoritative judge. It has no power to compel us, but it speaks with unquestioned authority. Of course we can and frequently do reject what morality commands, but when we do so we cannot avoid guilt or regret. It is because of our capacity for self-impeachment and remorse that Aristotle famously called man “the beast with the red cheeks.” Aristotle’s description holds up very well more than 2,000 years later. Even people who most flagrantly repudiate morality — say, a chronic liar or a rapacious thief — nearly always respond to detection with excuses and rationalizations. They say, “Yes, I lied, but I had no alternative under the circumstances,” or “Yes, I stole, but I did so to support my family.” Hardly anyone says, “Of course I am a liar and a thief, and I don’t see anything wrong with that.” What this means is that morality supplies a universal criterion or standard even though this standard is almost universally violated.
Morality is a surprising feature of humanity because it seems to defy the laws of evolution. Evolution is descriptive: It says how we do behave. Morality is prescriptive: It says how we should behave. And beyond this, evolutionary behavior appears to run in the opposite direction from moral behavior. Evolution implies that we are selfish creatures who seek to survive and reproduce in the world. Indeed we are, but we are also unselfish creatures who seek the welfare of others, sometimes in preference to our own. We are participants in the fame of life, understandably partial to our own welfare, while morality stands aloof, taking the impartial, or “God’s eye,” view, directing us to act in a manner conducive to the good of others. In sum, while evolution provides a descriptive account of human self-interest, morality provides a standard of human behavior that frequently operates against self-interest.
So if we are mere evolutionary primates, how to account for morality as a central and universal feature of our nature? Why would morality develop among creatures obsessively bent on survival and reproduction? Darwin himself recognized the problem. In The Descent of Man, Darwin argued that “although a high standard of morality gives but a slight or no advantage to each individual man and his children over the other men of the same tribe, yet . . . an advancement in the standard of morality will rtainly give an immense advantage to one tribe over another.” Darwin’s point is that a tribe of virtuous patriots, with each of its members willing to make sacrifices for the group, would prove more successful and thus be favored by natural selection over a tribe of self-serving individuals. This is the group-selection argument, and for many decades it was considered an acceptable way to reconcile evolution with morality.
But as biologists now recognize, the argument has a fatal flaw. The question we have to ask is how a tribe of individuals would become self-sacrificing in the first place. Imagine a tribe where, for instance, many people shared their food with others or volunteered to defend the tribe from external attack. Now what would be the fate of individual cheaters who benefited from this arrangement but hoarded their own food and themselves refused to volunteer to fight? Clearly these scoundrels would have the best deal of all. In other words, cheaters could easily become free riders, benefiting from the sacrifices of others but making no sacrifices themselves, and they would be more likely to survive than their more altruistic fellow tribesmen.