Ode to a Nightingale Theme of Versions of Reality

It's hard to pinpoint exactly when the poem leaves the "normal" world, because the speaker's version of "normal" involves acting like he's on the drug opium. But by the fourth stanza it has become clear that he has joined the nightingale in a dark, lush fantasy world. His journey takes him close to the experience of death, but the spell is broken when the bird flies away unexpectedly. The entire poem is characterized by the speaker's "altered" mental state, which he claims is not due to alcohol or drugs, although he compares it to these things.

1. Is there a divide between the real and fantastic worlds in the poem, or is the entire poem a fantasy?
2. What is the role of wine, drugs, and drunkenness in the speaker's imaginative journey?
3. Why is he unable to continue dreaming about the nightingale after it has flown away, and what does this say about the nature of reality versus fantasy?
4. What does the speaker mean when he says that he wants to "fade away" (line 20)?

The fantasy of the poem begins in stanza four, when the speaker escapes to the forest on the wings of poetry.

Keats wants the reader to think that his experience is identical to a state of extreme drunkenness or intoxication – only not caused by any kind of drug.