The author argues that Instructional Design (ID) is a problem-solving process, not a procedure, made up of a thinking process common to designers in many fields, and a set of well-accepted, underlying ID principles. This article presents a model of those principles. Further, it argues that teaching ID as a well-structured procedure is not helpful to people trying to learn it, and that ID should be taught in the context of principles and heuristics instead. (Contains 3 figures and 1 table.)