ABSTRACT
The word teach is derived from the Old English tacn, which meant something like “sign”—and by which any object or event could potentially serve as a teacher. The act of teaching, that is, was originally understood strictly in terms of its effects on the learner, not at all in terms of any deliberate effort to affect learners. To teach was to perturbate; a teaching was, to borrow from Gregory Bateson, any difference that makes a difference.2
