Final answer:
The theme of the provided stanza from Keats' 'Ode to a Nightingale' concerns mortality, as it highlights the speaker's desire to escape the pain and suffering associated with human life.
Step-by-step explanation:
The stanza from Keats' "Ode to a Nightingale" largely revolves around the theme of mortality. The speaker begins by expressing a sense of physical numbness and desire to escape, perhaps from the pain of being mortal, which is conveyed through the references to hemlock and opiate.
This indulgence in thought of a nightingale, a creature that seems unburdened by human troubles, highlights the speaker's yearning to be free from the sorrow associated with human life. The nightingale's song embodies the beauty of nature and the speaker's longing to leave behind the world of suffering, thus reflecting on mortality and the human condition.
In addition, the contrast between the immortal nightingale and the mortal human emphasizes the theme of mortality even more deeply.