By examining the general conditions in which a structure could come to represent another state of affairs, it is argued that beliefs, a special class of representations, have their contents limited by the sort of information the system in which they occur can pick up and process. If a system—measuring instrument, animal or human being—cannot process information to the effect that something is Q, it cannot represent something as Q. From this it follows (for simple, ostensively acquired concepts at least) that if an organism that has the information-processing capabilities for knowing that something is Q.