The essay reviews some of the philosophical justifications that underlie methods of teaching writing, citing classical rhetoric (in the European tradition) as the source of these assumptions in the conflict between Plato and the Sophists over the ethical problem of teaching an art of persuasion. The three philosophical justifications for teaching that I discuss are (1) Teaching students formal strategies of argument that give them power over others by manipulating their beliefs. (The Sophists) (2) Teaching students pure reasoning so that they will not be deceived by the strategies of persuasive discourse. (Plato) (3) Teaching as a process of discovering sharable grounds for agreement on issues not subject to pure reason. (Aristotle). It is the third justification that best warrants the teaching of across the curriculum as a way to write to rather than to write, because it is this justification that imagines a world of discourse in which people disagree about fundamental questions and yet strive to reason together toward mutual understandings, i.e. the basic condition of university inter‐disciplinarity. This essay therefore addresses, “how to imagine alternatives to technical competency as a basis for using to learn the knowledge of disciplinary fields.” This essay is a version of a talk I gave at Sogang University in the Humanities Forum on April 15, 2009, at the invitation of Professor Yoan Lee and the English Department. The occasion was to assist the Humanities faculty in thinking about writing across the curriculum, an idea that is * University of Oregon