In this chapter I clarify some of the epistemological considerations, concerning the concepts of environment and communication, that arise from the radical constructivist approach to the problems of knowing. Radical constructivism is, indeed, a theory of knowing, and it is radical because it differs radically from traditional theories of knowledge. It would seem appropriate, therefore, to preface the discussion of the two key concepts with a few preliminary remarks about constructivism, a term that has recently become quite fashionable and, consequently, is frequently being used in ways that do not seem compatible with the approach I intend to discuss here.