What are the Romantic elements in "Isabella; or The Pot of Basil" by John Keats?

Some of the more prominent signs of aesthetic philosophy
behind Romanticism apparent in John Keats' "Isabella; or, The Pot of Basil" are (1) the
preference for individual experience over universal experience; (2) the preference for
powerful emotion and feeling; (3) the preference for emotion over reason; (4) and the
preference for symbolism and suggestion over clarity of text. The opening lines of
Keats' poem show the poem's orientation to the individual over the general and
universal:

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Fair Isabel, poor simple Isabel!   

Lorenzo, a young palmer in Love’s
eye!

Lines 3 through 8 begin
the journey of overflowing powerful emotion, representing both the subject's emotion and
the poet's emotion:

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They could not, sure, beneath the same roof
sleep   
But to each other dream, and nightly
weep.

Stanza IV reveals the
orientation of the poem toward emotionality over
reason:

So
spake they to their pillows; but, alas,   
Honeyless days and days did he let
pass;

Lines 69 and 70
illustrate the reliance on symbol over direct clarity of
expression:

So
said, his erewhile timid lips grew bold,   
And poesied with hers in dewy
rhyme:

Further examples of
each are apparent throughout but these early ones set up the orientation of the
poem.

One of the revolutionary accomplishments of
Romanticism, for better or worse, was to overturn the ancient and enduring
presupposition, restated by Elizabethan Philip Sidney, that poetry is a divinely
inspired vehicle for imitating the ideals on the heavenly sphere for the instruction of
humanity. By emphasizing the individual and individual experience and making the poet
the source of poetic inspiration as opposed to a divine poetic inspiration, the Greek
and Renaissance philosophy of poetic aesthetic philosophy was reversed. Coupled with
this was the idea of the preeminence of the poet, so the voice of the speaker of the
poem came to be oftentimes the voice of the poet.

[For more
infomation, see href="http://academic.brooklyn.cuny.edu/english/melani/cs6/rom.html">"Romanticism" by
L. Melani, Brooklyn College, NY from which this answer is
drawn.]