Imagine the following scenario: You have two different tribes, your collectivist tribe over here—where everything's in common, and your individualist tribe over there. Imagine these tribes not only have different ways of cooperating, but they rally around different gods, different leaders, different holy texts that tell them how they should live—that you're not allowed to sing on Wednesdays in this group, and in this group over here, women are allowed to be herders, but in this group over there, they're not; different ways of life; different ways of organizing society. Imagine these societies existing separately, separated by a forest that burns down. The rains come, and then suddenly you have a nice lovely pasture, and both tribes move in.
Now the question is: How are they going to do this? We have different tribes that are cooperative in different ways. Are they going to be individualistic? Are they going to be collectivists? Are they going to pray to this god? Are they going to pray to that god? Are they going to be allowed to have assault weapons or not allowed to have assault weapons? That's the fundamental problem of the modern world—that basic morality solves the tragedy of the commons, but it doesn't solve what I call the "tragedy of common sense morality." Each moral tribe has its own sense of what's right or wrong—a sense of how people ought to get along with each other and treat each other—but the common senses of the different tribes are different. That's the fundamental and moral problem.
JOSHUA D. GREENE is the John and Ruth Hazel Associate Professor of the Social Sciences and the director of the Moral Cognition Laboratory in the Department of Psychology, Harvard University. He studies the psychology and neuroscience of morality, focusing on the interplay between emotion and reasoning in moral decision-making. His broader interests cluster around the intersection of philosophy, psychology, and neuroscience. He is the author of Moral Tribes: Emotion, Reason, and the Gap Between Us and Them.