This chapter looks at practical knowledge, as knowledge—the way it is structured, the kinds of generalizations it affords, the ways in which it is related to the practical context on which it bears. The chapter discusses three basic terms: rule of practice, practical principle, and image. The rule of practice is simply what the term suggests—a brief, clearly formulated statement of what to do or how to do it in a particular situation frequently encountered in practice. The practical principle is a more inclusive and less explicit formulation in which the teacher's purposes, implied in the statement of a rule, are more clearly evident. The third level, that of image, is at once the least explicit and most inclusive of the three. On this level, the teacher's feelings, values, needs and beliefs combine as Sarah forms images of how teaching should be, and marshals experience, theoretical knowledge, school folklore, to give substance to these images.