The main theme of the poem is the conflict the narrator experiences between Self and Soul, with the Self, representing life, winning the debate.
The speaker is an old man, and the Soul is in dialogue with him. The Soul asks him to transcend his earthly Self and think of what is to come after he dies. The Soul argues that the speaker should ponder eternity (the "quarter where all thought is done"):
Fix every wandering thought upon
That quarter where all thought is done
The Self, however, stays stubbornly fixated on the earthly. He thinks about the "consecrated blade upon my knees," a phallic, erotic symbol of life on earth. The Self is not ready to give up what is potent and life giving.
The Soul continues to push back, asking the Self why a person should:
Long past his prime remember things that are
Emblematical of love and war?
But while the Soul tries to turn the Self's thoughts towards death, the Self clings relentlessly to the worldly.
In the second stanza, the voice of the Soul, earlier in dialogue and debate with the Self, is silenced. In this stanza, the Self affirms life, saying he would be "content" to live it all over again. He states:
We must laugh and we must sing,
We are blest by everything,
Everything we look upon is blest.
Yeats's perspective on death is different from that of other poets who write about the end of life. Most poets writing about the end of life counsel paying attention to the soul and preparing oneself for what is to come. In contrast, Yeats's speaker seems determined to double down on experiencing all the fullness of life, despite his old age.