Definitions, like mythologies, wear out. It is then important to replace them. Aladdin’s wife had a choice, but we have none. We must change our old lamps for new, or sit in the dark. A natural philosopher who retained the mythological definition of thunder could not speak of lightning to young men who had learnt of electricity without an air of irrelevance of which he might be quite unconscious. Not so his listeners, who would brush his explanations impatiently aside as soon as they knew the beliefs on which he based them. Whenever historians or critics seem irrelevant, we are safe in assuming a difference between their definitions and our own. When they seem irrelevant to many people beside ourselves, we can go further and assume that their definitions are either worn out or not yet accepted. Sometimes, of course, they are without definitions either old or new, but then they need not trouble us, for they disappear like cuttle-fishes in the darkness of their own ink. There is at the present day a widespread dissatisfaction with historians of literature. It is impossible not to feel that their dicta do not matter, that their sense of perspective is wrong or uncertain, that their books are of no use to us except as bibliographies. A new definition of literature is needed, that shall give them some scale, some standard to which they can refer. For without such standard or scale, they can do no more than gossip, or judge poetry by its passion, by its sense, by its smoothness, or by any other half-remembered scrap from a definition that is no longer adequate. If we would get rid of these irrelevancies, and write histories of literature that shall deal with the matter of which they propose to treat, we must find a new standard of values, and to find that we must make a new definition. We must have a statement of the nature of literature applicable not to the books of one nation of one time only, but to those of all nations and of all times. It must supply us with terms in which we can state the aims of widely different schools and writers, with regard to their medium and not to any accidental quality. If it is to do that we must escape from the prejudices of our own time (which may be invisible to us) by seeking our formula in a definition of the medium common to all writers, a statement of the function of words in combination.