Yeats published "Sailing to Byzantium" in The Tower (1928), at a time when he himself was facing old age and illness, and four years after he had left his native Ireland on a trip to Italy to view Byzantine art. In the first stanza, it shows the poet leaving his place of residence, "no country for old men" because of its exuberant but mindless fertility, which ignores and even mocks the facts of aging and death:

Fish, flesh, or fowl, commend all summer long
Whatever is begotten, born, and dies.
Caught in that sensual music all neglect
Monuments of unaging intellect.

Time has taken this option away from the poet here. He can no longer take comfort in the physical and must, to further defy age and death, give himself over to the spiritual and immutable:

An aged man is but a paltry thing,
A tattered coat upon a stick, unless
Soul clap its hands and sing, and louder sing
For every tatter in its mortal dress,

He has therefore set out on a quest to Byzantium, the poem's symbol for an ageless system of spiritual truth, hoping that by integration with this system, he can halt or defy age:

Consume my heart away; sick with desire
And fastened to a dying animal
It knows not what it is; and gather me
Into the artifice of eternity.

Thus, in "Sailing to Byzantium," old age is the force and the threat that has impelled the poet to leave behind the temptations of exuberant physicality and the pride of the body, to attempt to seek eternal life in some divine and abstract pattern. Old age has robbed him of his illusions, and sent him on a desperate quest to go "out of nature" in search of eternal truths and eternal life.