The Tragedy of King Lear
The play which is in the title of this poem is a tragedy by William Shakespeare that is often considered his greatest achievement. The play is juxtaposed against lesser "Romances” right from the first line. The profundity of Lear is put forth as a symbol of the greatest heights that poetry can reach.
William Shakespeare
The speaker extols Shakespeare as the "Chief Poet" of "Albion." Albion is a historical allusion signifying England as a concept rather than merely a country. Keats is essentially saying that Shakespeare symbolizes British literature as its singular greatest poet. King Lear, of course, is a play, but it is written mostly in verse.
Bitter-Sweet Fruit
The speaker refers to King Lear as the "bitter-sweet of Shakespearean fruit." Within the context of the poem, this could refer to the idea of enjoying the artistry of a superior talent while also suffering envy. The bitter-sweet fruit may symbolize the ability to sweetly admire the work of a peer while at the same time feeling a bitter sense of inferiority.
Syren
The "fair-plumed Syren" mentioned in the second line refers to the figures of mythology who lured sailors to their doom by singing a beautiful and hypnotic song. In this contest, Syren symbolizes procrastination of a sort. The speaker is tempted to either read or write the lesser poetry of Romance. His decision to read Lear again is a denial of this temptation.
The Phoenix
The Phoenix is another allusion to ancient myth. It references a bird that is resurrected through fire. The poem ends with the speaker referring to reading Lear as being consumed by fire. He hopes this will result in a rebirth of his own creative ambitions to pursue the nobler literature of Shakespeare than the lesser Romances. The Phoenix retains its symbolism of rebirth and resurrection.