William Morris has for many years now been considered a minor figure in Victorian literature. His poetry, which enjoyed immense popularity in the nineteenth century, has become unfashionable, and his prose writings, which have never been popular except with a few poets seem very widely underestimated in academic circles~ even where they are read at all. On the other hand, his fabrics and wall-paper designs have never been more popular, and he is still quite well-known as a political figure, with the result that these aspects have dominated most writing on him since the Second World War, while his literary work has been largely ignored, or only treated by critics in other fields who have not felt themselves qualified to appraise his work in this area on any scale. This lack of concern for Morris's literary work, and particularly for his prose romances, which have been most unjustly neglected, has come about chiefly through two factors: the changes in taste which have caused twentieth century critics to be chiefly interested in lyric poetry and in the novel, instead of in narrative poetry and in the prose romance; and the resulting ignorance about the conventions of these genres which have led them to judge Morris's work by inappropriate norms. That Morris's work is relevant to the twentieth century is shown by the new non-academic revival of interest in his prose romances, and it seemed that the time had come when a serious attempt should be made to understand just what Morris was trying to do in his poetry and prose, and how far he succeeded. This thesis attempts therefore to distinguish a line of development in Morris's aesthetic theory, working from his writings on art and on literature, to analyse that development, and to apply it to his literary work. The thesis thus falls into five parts: a section which deals with critical attitudes to Morris and the break-down of suitable critical terminology for judging his work which has brought about his present low status; two sections setting out Morris's aesthetic theory in design-work and literature; and two sections in which this theory is related to his literary achievements in the earlier and the later work. This means that the thesis considers at least briefly most of Morris's literary production, but main areas of concentration are on the early prose tales, The Earthly Paradise, and the late prose romances. The resulting picture of Morris's theory and practice shows how his thought and art, modified by the needs of his political ideals, developed from his early naive work in design and literature towards a much more sophisticated art, which can be read on a number of levels, in which his wide knowledge of myth and legend and his own symbol-system taken from the world of nature blend in equal parts. Doctor of Philosophy (PhD)