We recognize Robert Louis Stevenson’s Long John Silver by his commanding presence, his stoicism and the absence of his left leg, cut off below the hip. Although we think we know the roguish Silver, characters such as he are not of this world, as Stevenson himself admitted in Longman’s Magazine in 1884. He described fictional characters as being like circles—abstractions. Scientists use circles to solve problems in physics, and writers and readers likewise use fictional characters to think about people in the social world.