Introducing his collection, Yeats invites the rose close to him as he sings the ancient songs of Ireland. He will sing of druids, and of Cuchulain.
He again invites her to come near, to avoid hearing small, narrow thoughts. He does not want her too near, however, because then all he could hear would be the "bright things" said to the dead by God, and learn a language nobody knows anymore.
Yeats addresses this poem to the rose, the unifying symbol of the collection. Typically the rose symbolized a nationalist vision of Ireland, feminized in the character "Roisin Dubh," which translates, "the black rose." The rose also symbolizes Maud Gonne, a female revolutionary with whom Yeats was deeply in love. Her nationalist politics, coupled with her dark beauty, resonate with the wild, beautiful symbol of Ireland.
The ancient figures whom Yeats promises to sing about include druids, who were healers and priests in Ancient Ireland. He also promises to sing of Cuchulain, the hound of Culain, who is the great hero of the Irish myth cycles.
Yeats's hesitation to allow the rose to come too near can be read a number of ways. On the one hand, it represents his wish to sing about "common things" in addition to "strange things." He insinuates that if the rose comes too near, he will only write poetry about high, abstract, beautiful things - about the strange miracles of God. Yeats wants also to address common, lowly subjects - "the weak worm" and "the field mouse." Thus he expresses a desire to poeticize all of Ireland, from the field mice to the religious truths.
Moreover, Yeats' hesitation expresses his ambivalence about Irish nationalism. One could read his hesitation as expressing anxiety that if he communes to directly with the feminized Ireland he will be infected with the desire to rebel, and with a fanaticism for the dead which usually characterized Irish nationalists before 1916. The dead language to which Yeats refers is Gaelic. If he were to come too close to the rose, he suggests, he would write poetry in this ancient language, thus rendering his poems useless in addressing a wider society.
In short, Yeats wants to do justice to "the rose" - i.e. to Ireland - without fully identifying with it, thus leaving him room to translate his homeland for a wide literary audience. He wants to capture the spirit of his land without become overwhelmed by that spirit. He wants to celebrate Ireland, but always with critical distance.