It was composed soon after his "La Belle Dame sans Merci" and his odes on Melancholy, on Indolence, on a Grecian Urn and to a Nightingale and just before "To Autumn".
According to Michael O'Neill, Lamia in the poem "is treated ambivalently but with considerable sympathy", making "a sharp contrast with the more leisurely and seemingly uncritical use of romance in [the] two narrative poems that follow ... the hapless Lycius is caught between the reductive rationalism of Apollonius and the bewitching illusoriness of Lamia.
"[2] At the "immortal dinner party" held by Benjamin Haydon on 28 December 1817, Keats agreed with Charles Lamb that Newton "had destroyed all the poetry of the rainbow, by reducing it to the prismatic colours".
Philosophy will clip an Angel's wings, Conquer all mysteries by rule and line, Empty the haunted air, and gnomed mine— Unweave a rainbow, as it erewhile made The tender-person'd Lamia melt into a shade.
[5] The book Unweaving the Rainbow by Richard Dawkins takes its title from the above-quoted passage: it is an explicit attempt to demonstrate that this view of "cold philosophy" is incorrect and that science reveals, rather than destroys, the true beauty of the natural world.