This thesis looks at the writing and the painting of Walter Sickert and in particular at his part in the critical debate in art at the end of the nineteenth and the beginning of the twentieth centuries. Falling between the period in which Ruskin’s theories of art had been influential on the work of contemporary painters and the advent of the Modernist orthodoxy heralded by the writing of Roger Fry and Clive Bell, this period was viewed with extreme pessimism by many of the art critics of the day. The younger generation of English painters was looking towards France for its ideas, and an examination of the New Art Criticism reveals the influence of French art criticism. Sickert’s earliest art criticism is largely unknown but examined here, in the context of the other New Critics, it reveals the full extent of his understanding of French art and the significance he attached to the subject matter of paintings. It also helps to explain why he later found the theories of Fry and Bell so noxious. By examining Sickert’s earliest writing on art and by following the development of his ideas through both his painting and his later writing it is possible to place his late, and somewhat idiosyncratic, paintings within the context of a consistent ideology. While Sickert’s ideas may have appeared somewhat reactionary at the time, the subsequent decline of the Modernist ideology and the aesthetics that have developed since, all suggest that Sickert’s theory and practice was striving towards a definition of modern painting defined by its concern with the modern human condition.