The book summarizes the different Muse traditions that were congenial to Yeats and shows how his perception of these women as Muses underlies his poetry. Newly available letters and manuscripts are used to explore the creative process and interpret the poems.Because Yeats believed that lyric poetry 'is no rootless flower, but the speech of a man,' exploring the relationship between poem and Muse brings new coherence to the poetry, illuminates the process of its creation, and unlocks the 'second beauty' to which Yeats referred when he claimed that 'works of lyric genius, when the circumstances of their origin is known, gain a second a beauty, passing as it were out of literature and becoming life.'