The purpose of this research is to study the Yeat's view on the good and evil in human nature. Throughout his life, Yeats has made a spiritual, mystical and mythological world in which he tries to portray the eternally dichotomized nature of human consciousness. Yet, he attempts to harmonize the antinomies, the contraries that highlight human nature. Yeats's life and art is full of such attempts to unify harmoniously opposite forces: body and soul, good and evil, light and darkness, the sun and the moon, the antithetical and the primary, etc.. In this almost impossible unison of conflicting forces, Yeats hopes to find the unity of the two. For Yeats, instinct without spirituality, intellect without emotion, wisdom without action, and good without evil can only express a part of human nature, and he refused to deny one side of human being. He did not want to separates his soul from matter, good from evil but to find the perfect balance and attain the assertion of the 'Unity of Being.'