One of the most important elements in Yeats' thought is his view of the tragic basis of art. This conception, which can best be called a tragic aesthetic, was developed shortly after 1900 in three prose works--certain fragments of the Samhain publication (1904), "Poetry and Tradition" (1907), and "The Tragic Theatre" (1910). The tragic view developed in these essays became the conceptual basis behind much of Yeats' poetry and therefore played a central role in the direction of his career. This thesis traces the lineaments of Yeats' tragic aesthetic in these early essays, determining its outline in the dreamy, often vague language in which it is expressed, and shows its impact on his poetry from 1904 to the end of his career in 1939.