Which two themes are being highlighted by Keats in this poem. What different images he has used to present them?

John Keats uses the image of the knight and the spectral maiden to denote courtly love and unrequited love. He also uses the absence of the birds' song and the withering of nature to denote decay and the deterioration of earthly emotion.

O what can ail thee, knight-at-arms, Alone and palely loitering? The sedge has wither’d from the lake, And no birds sing.

The images of isolation and "palely loitering" begin the theme of unrequited love.

O what can ail thee, knight-at-arms, 5 So haggard and so woebegone? The squirrel’s granary is full, And the harvest’s done.

Harvest time is over and the world is preparing for the cold, long winter ahead.

I see a lily on thy brow With anguish moist and fever dew; 10 And on thy cheek a fading rose Fast withereth too.

Lilies denote death, decay, and deterioration. Love and our physical bodies deteriorate.

I met a lady in the meads, Full beautiful—a faery’s child, Her hair was long, her foot was light, 15 And her eyes were wild. I made a garland for her head, And bracelets too, and fragrant zone; She look’d at me as she did love, And made sweet moan. 20

these stanzas develop love, courtly love, and traditions of tenderness.

I set her on my pacing steed And nothing else saw all day long, For sidelong would she bend, and sing A faery’s song. She found me roots of relish sweet, 25 And honey wild, and manna dew, And sure in language strange she said— “I love thee true.” She took me to her elfin grot, And there she wept, and sigh’d full sore; 30 And there I shut her wild wild eyes With kisses four. And there she lullèd me asleep, And there I dream’d—Ah! woe betide! The latest dream I ever dream’d 35 On the cold hill’s side. I saw pale kings and princes too, Pale warriors, death-pale were they all; They cried—“La Belle Dame sans Merci Thee hath in thrall!” 40 I saw their starv’d lips in the gloam, With horrid warning gapèd wide, And I awoke and found me here, On the cold hill’s side. And this is why I sojourn here, 45 Alone and palely loitering, Though the sedge is wither’d from the lake, And no birds sing.

The last few stanzas develop the theme of dreams and dreaming. The knight is in love, but the love is for one who belongs to another realm of existence and he cannot have her. The knight is held captive and powerless before such love. It is insinuated that this love will turn into death for the knight. At the end of the poem we are left as the poem begins with images of birds not singing, images of withering, and of the knight alone.