I know only a tiny fraction of what there is to know. And I know this. And you are no different, whoever you are. Maybe things were not always like this. Maybe we used to live in a less complicated world, in which we all knew, or could easily know, much of what there was to know: things about family, culture, hunting, and gathering. But that is not the world we live in now. In modern societies, there is an extensive and thorough division of labor. And with that division of labor comes a division of knowledge. This chapter isn’t about the causes or explanation of this phenomenon. It is, however, about a distinctive problem that arises from this phenomenon: the problem of asymmetric ignorance.