What is the message of the poem "Leda and the Swan," by W.B. Yeats?
If "Leda and the Swan" can truly be said to have a "message," it is perhaps one that can also be identified in another of Yeats's poems, "The Second Coming," in which the "rough beast" of Revelation finds "its hour come round at last." This poem ends as the end of the world begins: in it, an instance has changed everything. In the same way, "Leda and the Swan" is a vivid description of one moment in time that leads to the end of one age and the beginning of a new one.
As detailed in the above answer, the rape of Leda is an occurrence which can be identified as the end of the mythic era and the beginning of modern history: at that moment, we cease to speak of gods and begin a study of the recorded deeds of men. One message of the poem, then, may be that a seemingly insignificant event such as a copulation—"a shudder in the loins," deliberately minimized in importance here by Yeats—can change far more than we could ever anticipate.
We could read other messages into this poem. Its powerful imagery captures the senses: the "blow" and the "great wings beating" make the reader feel their strength. Accordingly, Leda must surrender to the strength of the swan, but also become almost one with it, feeling "that strange heart beating where it lies." The strong is overwhelmingly the stronger of the two, but at the end of the poem, the poet asks whether Leda "put on his knowledge with his power"—that is, did she take into herself the knowledge and power of Zeus when he raped her? This is an interesting idea, suggesting perhaps that, in violating Leda in this way, the god has also surrendered some of his own power. We might infer from this a secondary message that violence diminishes the strong, as well as hurting the victim.
In "Leda and the Swan", Irish poet William Butler Yeats takes the traditional form of the Petrarchan sonnet and fills it with an image evoking a powerful aesthetic experience. The image is Zeus's rape of Leda, in Greek mythology, daughter of Thestios, king of Aetolia, and wife of Tyndareus, king of Sparta. Assuming the form of a massive swan for the violent seduction, Zeus fathers the twins, Castor and Pollux, and Helen of Troy, peerless in beauty in all the world. This moment of conception, rendered in the sonnet's transition from the octave to the sestet as "a shudder in the loins" conveys the principal message of the poem: Leda's savage impregnation is the genetic blueprint for the Trojan War - "the broken wall, the burning roof and tower
and Agamemnon dead" - the rise of Greek civilization, and the unfolding history of the West. The poetic transition in fact objectifies the end of the mythological world and the beginning of history.