This paper formulates a semiotic metatheory (theory of change) of human communication, in six analytical steps: First, semiology indicates that the coding function in communication relies on the nature of the signifier and the signified. Second, the nature of coding (as distinct from its function) is best described by social systems theory. Third, human communication is best accounted for by communication theory, not by information theory. Fourth, any metatheory of human communication based on the foregoing hypotheses can have only two functional models in the social world. Fifth, these two models, called the ecosystem model and the phenomenological model, constitute the logical universe of a rigorous science of communication. Sixth, these models presume a semiotic base in which description and information are code conditions, definition and communication are context conditions, and interpretation and legitimation are message conditions. (Author/RL)