My heart aches, and a drowsy numbness painMy sense, as though of hemlock I had drunk,Or emptied some dull opiate to the drains

One minute past, and Lethe-wards had sunk:‘Tis not through envy of thy happy lot,But being too happy in thine happiness,—That thou, light-winged Dryad of the treesIn some melodious plotOf beechen green, and shadows numberless,Singest of summer in full-throated ease.–//–
The songbird is a happy nightingale, a voice that compels the narrator to join with in and forget the sorrows of the world. However, Keats had recently suffered the loss of his brother. The song’s conclusion represents the result of trying to escape into the realm of fantasy.
Fade far away, dissolve, and quite forgetWhat thou among the leaves hast never known,The weariness, the fever, and the fretHere, where men sit and hear each other groan;Where palsy shakes a few, sad, last gray hairs,Where youth grows pale, and spectre-thin, and dies;Where but to think is to be full of sorrowAnd leaden-eyed despairs,Where Beauty cannot keep her lustrous eyes,Or new Love pine at them beyond to-morrow.–//–
Away! away! for I will fly to thee,Not charioted by Bacchus and his pards,But on the viewless wings of Poesy,Though the dull brain perplexes and retards:Already with thee! tender is the night,And haply the Queen-Moon is on her throne,Cluster’d around by all her starry Fays;But here there is no light,Save what from heaven is with the breezes blownThrough verdurous glooms and winding mossy ways.–//–
The nightingale described within the poem experiences a type of death but does not actually die. Instead, the songbird is capable of living through its song, which is a fate that humans cannot expect.
Darkling I listen; and, for many a timeI have been half in love with easeful Death,Call’d him soft names in many a mused rhyme,To take into the air my quiet breath;Now more than ever seems it rich to die,To cease upon the midnight with no pain,While thou art pouring forth thy soul abroadIn such an ecstasy!Still wouldst thou sing, and I have ears in vain—To thy high requiem become a sod.
–//–
Keats imagines the loss of the physical world and sees himself dead—as a “sod” over which the nightingale sings. The contrast between the immortal nightingale and mortal man, sitting in his garden, is made all the more acute by his imagination.
Thou wast not born for death, immortal Bird!No hungry generations tread thee down;The voice I hear this passing night was heardIn ancient days by emperor and clown:Perhaps the self-same song that found a pathThrough the sad heart of Ruth, when, sick for home,She stood in tears amid the alien corn;The same that oft-times hathCharm’d magic casements, opening on the foamOf perilous seas, in faery lands forlorn.–//–Forlorn! the very word is like a bellTo toll me back from thee to my sole self!Adieu! the fancy cannot cheat so wellAs she is fam’d to do, deceiving elf.Adieu! adieu! thy plaintive anthem fadesPast the near meadows, over the still stream,Up the hill-side; and now ’tis buried deepIn the next valley-glades:Was it a vision, or a waking dream?Fled is that music:—Do I wake or sleep?–//–
The poem ends with an acceptance that pleasure cannot last and that death is an inevitable part of life. To Keats there is something eternal in the contemplation of Beauty alone.
The poem celebrates what Keats described in a letter to his brothers as “negative capability.”
….that is, when a man is capable of being in uncertainties, mysteries, doubts, without any irritable reaching after fact and reason ……… with a great poet the sense of Beauty overcomes every other consideration, or rather obliterates all consideration.