Which poem by Keats depicts a protagonist so entranced by the imagination that he becomes alienated from the physical world of nature?

Correct answer: Ode to a Nightingale

In 'Ode to a Nightingale', the speaker uses poetry ('viewless wings of Poesy') to join the bird in its world of imagination. However, he eventually realizes that the 'fancy cannot cheat so well' and he is pulled back to his 'sole self'.