By the time Yeats was twenty-one, two concerns had already emerged as central in his writing. One, which endured little changed throughout his life, was his rejection of late-Victorian scientific rationalism in favor of Romantic forms of knowledge. His placement of “The Happy Shepherd” at the start of Collected Poems self-consciously signals the centrality of this choice to the formation of his canon. Claiming that the materialist approach of science has yielded only “Grey” and inhuman forms of truth, the poem declares that the realm of imagination, for all its uncertainty, offers the best chance of self-knowledge and solace in a “sick” and hurried world (VP64-5). The second concern, also enduring, but to which Yeats's relationship was often vexed and always evolving, was his desire to identify himself specifically as an Irish writer, and to assert the distinctiveness of “Irishness” as a cultural identity.
His interest in Irish folklore and heroic legend would bring these two seemingly separate preoccupations into intense and productive conjunction, particularly in the first two decades of his career. Folklore and legend offered him subject matter that contrasted sharply with the orthodoxies and concerns of the contemporary urban world, but that he was able to claim as distinctively Irish and draw on in creating master-myths of Irish nationality. As a storehouse of uncanny phenomena, ancient wisdom expressed in metaphorical or allegorical forms, and traditional models of story-telling, folklore appealed to him on occult, philosophical, and literary grounds. Heroic legend likewise attracted him both emotionally and intellectually, since he believed that only heroic action allowed the full expression of selfhood, and thus made possible the kind of passionate, heroic poetry he aspired to write (UPi 84).