Those who are involved in education are engaged in the acquisition and transmission of knowledge. But what is this knowledge which is being so acquired and transmitted and which is advanced with each generation? It is the twofold task of the philosopher to answer this question. The first part of his task is descriptive, it consists in setting out the essential characteristics of knowledge. The second part is both more problematic and more important; it is one of appraisal and evaluation. Each age has its cherished intellectual virtues and ideals. What these are is indicated by the terms of intellectual praise (like "wit", "learning" and "intelligence") current in everyday language. The terms favoured may change from time to time and the ideals enshrined in them may need restatement or defence. My aim in discussing knowledge in this paper is to defend one such ideal and to argue for an ancient epistemological principle which is in danger of being eroded because of the acceleration in the growth of knowledge and in the sheer accumulation of information. This principle urges that we should not merely advance what I shall call "bare knowledge" but cultivate an understanding kind of knowledge. The principle was, I believe, implicit in the Greek use of the word episteme, but it is unclear whether or not it is implicit in the modern English use of the word "knowledge".