To demonstrate how discourse tasks can differ in their cognitive difficulties, students in a graduate course on the teaching of writing participated in a procedure called "invisible writing." The purpose was to show the students that as they took on more cognitively demanding writing tasks, their ability to produce coherent discourse would be increasingly impeded by their inability to look back over their developing text. However, as the level of difficulty was raised from task to task, the students continued to insist that they found invisible writing no impediment to their thinking or to the coherence of the texts they were producing. This result suggests that writers who cannot look back over their sentences will retain them in their mind in a form resembling a reader's memory of the sentences that have already been read as they move forward through a text. From this it would seem reasonable to suppose that writers blocked by their verbal self-consciousness or by a tendency to compulsive overediting will find that invisible writing allows them to produce coherent first-draft prose more rapidly and copiously than they would have otherwise thought possible. Or, invisible writing may be used as a diagnostic instrument to see to what extent wandering attention or the distractions of premature editing are impediments for writers who seem unable to produce satisfactory quantities of prose in a single setting. (Appendixes include a scale of intellectual ascent for discourse, a sequence of writing tasks, and three writing samples from the invisible writing experiment.) (HOD)