A discussion of writing looks at research on the factors influencing written discourse and proposes a model of writing for academic purposes. First, studies of both cultural and individual aspects of the writing process are reviewed and the phenomenon of writing is viewed from both social and cognitive perspectives. The social perspective is that of purpose and audience, and the cognitive is that of a complex process of divergent thinking, incubation, idea organization, and activation of schemata. A model of school-based (academic) writing that considers the dimension of purpose (audience) and related cognitive processes (content) is then outlined and its implications for creation of writing assignments and the evaluation of writing are discussed. The model is based on a system of classification of written composition as documentary, constative (narrative, descriptive, or explanatory), or exploratory (interpretive or literary) and of the writing's dominant intention or purpose, the primary audience, the salient cognitive processes used, and its primary content. A 34-item bibliography is included. (MSE)