“Sailing to Byzantium” was written by Yeats at 60 or 61 and is his definitive critique of ageing, describing the agony of embodied existence as one inches toward death. His later works—from the 1920s on—are known for their occult orientations. In A Vision (1925), Yeats elucidates the intersection of his symbolism with various esoteric traditions, as well as his own philosophy, at the center of which is the “Great Wheel” or “gyre.” Hermetic traditions and societies were a cornerstone of the early 20th century, with many people conducting seances and attempting to connect with metaphysical beings. Yeats became well-known for his automatic writings in which spirits not only acted as muses for poetry, but were said to be channeled through the poet. In his essay "Magic" (1901), Yeats admitted he believes

[…] in the practice and philosophy of what we have agreed to call magic, in what I must call the evocation of spirits, though I do not know what they are, in the power of creating magical illusions, in the visions of truth in the depths of the mind when the eyes are closed (128).

“Sailing to Byzantium” also anticipates Yeats's foray into the world of eugenics, which he celebrated publicly in 1936 when he joined the Eugenics Society. The speaker’s journey to Byzantium is therefore not merely a means of escaping the body, but to change its makeup for posterity: The old do not belong in nature; their decrepitude is grounds for expulsion, while the young are perfectly suitable for country life, as they mirror the instinctive whims of animals. Yeats may have been a proud Irish man, but there were certain citizens in his homeland whom he viewed as imperfect, coinciding with the rhetoric of degeneration popularized in the 19th and 20th centuries and which culminated in the violence of Nazi Germany. In contrast to the fascist adaptation of the pseudoscience, Yeats’s fixation on eugenics was rooted in his Irish nationalism. In Estrangement (1926), he laments “the new ill-breeding of Ireland, which may in a few years destroy all that has given Ireland a distinguished name in the world” (p. 463). His fascination with eugenics coincides with Malthusian theories of overpopulation, and acts as a response to the modern world, developments in media, the rapid growth of cities, and the need for a birth-control policy in Catholic Ireland.