QUOTE : The most alarming rhetoric comes out of the dispute between liberals and conservatives, and it’s a dangerous waste of time because they’re both right. The perennial conservative concern about high taxes supporting a nonworking “underclass” has entirely legitimate roots in our evolutionary past and shouldn’t be dismissed out of hand. Early hominids lived a precarious existence where freeloaders were a direct threat to survival, and so they developed an exceedingly acute sense of whether they were being taken advantage of by members of their own group. But by the same token, one of the hallmarks of early human society was the emergence of a culture of compassion that cared for the ill, the elderly, the wounded, and the unlucky. In today’s terms, that is a common liberal concern that also has to be taken into account. Those two driving forces have coexisted for hundreds of thousands of years in human society and have been duly codified in this country as a two-party political system. The eternal argument over so-called entitlement programs—and, more broadly, over liberal and conservative thought—will never be resolved because each side represents an ancient and absolutely essential component of our evolutionary past. So how do you unify a secure, wealthy country that has sunk into a zero-sum political game with itself? How do you make veterans feel that they are returning to a cohesive society that was worth fighting for in the first place? I put that question to Rachel Yehuda of Mount Sinai Hospital in New York City. Yehuda has seen, up close, the effect of such antisocial divisions on traumatized vets. “If you want to make a society work, then you don’t keep underscoring the places where you’re different—you underscore your shared humanity,” she told me. “I’m appalled by how much people focus on differences. Why are you focusing on how different you are from one another, and not on the things that unite us?” The United States is so powerful that the only country capable of destroying her might be the United States herself, which means that the ultimate terrorist strategy would be to just leave the country alone. That way, America’s ugliest partisan tendencies could emerge unimpeded by the unifying effects of war. The ultimate betrayal of tribe isn’t acting competitively—that should be encouraged—but predicating your power on the excommunication of others from the group. That is exactly what politicians of both parties try to do when they spew venomous rhetoric about their rivals. That is exactly what media figures do when they go beyond criticism of their fellow citizens and openly revile them. Reviling people you share a combat outpost with is an incredibly stupid thing to do, and public figures who imagine their nation isn’t, potentially, one huge combat outpost are deluding themselves.