What is the poet's favorite technique?

Readers of this poem  may be interested to learn that
Keats had trained not as a poet or writer, but as an apothecary-surgeon. In the year of
this poem, 1816, he received his license to practice, but he gave up this career to
pursue a life of reading, thinking, and writing. The excitement he describes in this
poem explains that decision. One of the rhetorical figures usually associated with Keats
is synesthesia, the metaphorical mingling of references to
different senses. In line 7 of this poem, the word “serene” is both a political and
ecological metaphor, referring both to clear air and the majesty of Homer’s poetry. To
“breathe its pure serene,” by synesthesia, equates breathing with reading and also with
understanding. This was probably his favorite literary technique, though it is open to
debate.