 The information-based semantics for natural languages and content bearing mental states due largely to Dretske, Evans, Fodor, Lewis, Jackson, Recanati, and Zalta has led to refined theories of meaning and content in terms of informational relations. Such relations—information channels that allow information to flow from one part of a system to another—have proved to be so indispensable that they are in turn an object of research in their own right.