This book focuses on the two works in the subtitle as well as on unpublished manuscripts and notebooks in the Yeats collection of the National Library of Ireland. The author argues that by the end of the 1890s Yeats had developed a coherent symbolic system based on his work with Irish folklore and mythology and that this system is most clearly delineated in the first editions of the work and in Yeats’s unpublished papers. The book begins with a study of Yeats’s Irish and Celtic sources, then moves on to outline the symbolic theory, drawing heavily on Yeats’s notebooks. The theory is then applied in a critical study of the poems, prose, and plays of the last half of the 1890s.