This article proposes that two processes are involved in the generation of content during writing: (a) an active, knowledge-constituting process in which content is synthesized by constraints within semantic memory representing the implicit structure of the writer's understanding, and (b) a reflective, knowledge-transforming process in which content retrieved from episodic memory is manipulated in working memory to satisfy rhetorical goals. It suggests that, although both processes are required for effective writing, the contrasting nature of the implicit organization guiding the constitution of the writer's understanding and the explicit organization required to satisfy rhetorical goals is the source of a fundamental conflict in writing. The article starts by relating the processes to current models of writing. It outlines how they are combined in a dual-process model and discusses evidence for the model. The article concludes with a discussion of the implications for writing research and the teaching and development of writing.