This book provides the first exhaustive cross-linguistic typological study of how languages deal with the marking of information source: in particular those languages in which every statement must contain a specification of the type of evidence on which it is based: for example, whether the speaker saw it, or heard it, or inferred it from indirect evidence, or learnt it from someone else. Examples are drawn from over 500 languages from all over the world. This important book on an intriguing subject will interest anthropologists, cognitive psychologists and philosophers, as well as linguists.