The early Stoics taught that we are world citizens connected to all of humanity through our reason. Marcus Aurelius paints a graphic image in his “Meditations.” He jots his notes in the quiet of nightfall after a day of battle during the Germanic campaigns. The detritus of the battlefield is on his mind: Picture a hand and head lying apart from the rest of the body. This is what a person makes of himself when he cuts himself off from the world. We can’t be “at home in the world,” a Stoic catchphrase, if the good is reduced to self-interest, or grit is defined as go-it-alone self-reliance.