The poetry of Japan takes the human heart as seed and flourishes in the countless leaves of words. Because human beings possess interests of so many kinds, it is in poetry that they give expression to the meditations of their hearts in terms of the sights appearing before their eyes and the sounds coming to their ears. Hearing the warbler sing among the blossoms and the frog that lives in the waters—is there any living thing not given to song? It is poetry which, without exertion, moves heaven and earth, stirs the feelings of gods and spirits invisible to the eye, softens the relations between men and women, calms the hearts of fierce warriors.
—Ki no Tsurayuki (868-945), the preface to Kokinshū
(quoted in The Princeton Companion to Classical Japanese Literature, Princeton Univ. Press, 1985)