An attempt is made by means of communication theory to build a single conceptual scheme that describes the transmission of messages from one man's brain through the medium of speech into another man's brain. It emphasizes the resemblance of speech production to an encoding process, and the resemblance of the hearing and interpreting of speech sounds to a cryptanalytic procedure that depends on the known conditional probabilities of the language. It is pointed out that speech sounds, or phones, form an infinite, continuous set, while phonemes, the smallest significant units of the cipher, are a discrete small set. It is felt that a logical method of decoding can be set up only through the convergent behavior of language as a statistical process.