Much of what we know comes, in one way of another, from believing what other people say. Facts about geography, history and science would be simply beyond us if believing the testimonies of other people were not way of coming to know things. In this book, Stephen Wright investigates the way in which knowledge transmitted from the testimony of others is unlike knowledge from other sources, such as instruments. He begins by explaining what what transmission is, considering objections to transmission raised by the case of creationist schoolteachers, and assesses contrasting theories of testimony from internalism, externalism and reliablisim. He argues that not only can believing testimony bring us to know what other people know, it can, in the right circumstances, bring us to acquire their knowledge. This makes testimony unlike other sources. He argues that this comes from the distinctive features of how we interact with one another as humans.