To develop a theory of invention that would include both generation and selection of material for written composition, the four major current theories of invention were considered. Since only one--prewriting--included a selection component and was limited in several ways, a psychotherapeutic theory--focusing--was adapted to the composing process in accordance with the principles that underlie adequate rhetorical theories. The resulting theory, which focuses on the composition process, was field tested to extend and refine it and to develop methods for its use in a wide variety of writing situations. The theory and methods enabled writers to generate and select material through a single coherent and widely adaptable procedure. Five patterns for different kinds of writing--i.e., personal narratives, literature, assigned subjects, comparison/contrast and other essay development types, and persuasion--were developed. (Author/CRH)