What do you see as the primary distinctions between the early and late Romantic poets? What themes are most important for the early Romantics, and...

The
principal differences between the first generation of Romantics--Blake,Wordsworth, and
Coleridge-- and the later generation of Byron, Shelley and Keats need to be understood in the
context of the political events of the period from the 1790's through the 1820's.

Both Wordsworth and Coleridge reached adulthood in the early years of the French
Revolution. Blake was about 15 years older, but he was affected by the same spirit of the
Revolution as the other two. This was a time when, as Wordsworth stated,

Bliss was it in that dawn to be alive,

And to be
young was very heaven.

The early Romantics were basically
optimists, looking forward to a positive future for a humanity that would be liberated from the
old constraints andthe older, oppressive ways of thinking. Despite the supernatural horrors it
depicts and its suffering, The Rime of the Ancient Mariner is a hopeful
work with a positive message. In The Prelude Wirdsworth chronicles his
maturation and sees unlimited vistas for man, in which one can cross the Alps and feel that one
is over the crest without even knowing it, so powerful a being has man become.

The second generation, on the other hand, were largely pessimistic. They came of age
during the Napoleonic wars, when France had become a dictatorship threatening and subjugating
most of Europe. Not only were the ideals of the Revolution subverted in some sense, but the
outcome in 1815, with Napoleon's final defeat, represented a victory for the reactionary forces
in both Britain and on the Continent. Byron, in both Childe Harold and
Manfred, expresses a deadened, hopeless feeling in which his protagonists
brood darkly and wish for "forgetfulness." Even in his satiric and comical
Don Juan, Byron is focusing largely upon the darker side of the human
spirit. Though Shelley in his "Ode to the West Wind" asks rhetorically,

If winter comes, can spring be far behind?

the general tenor of the poem seems burdened by despair,in which
the poet likens himself to the forest in autumn and, though he wishes to be empowered by the
West Wind, must ask,

What if my leaves are falling like
its own?

Keats, in his most famous poems, laments his
isolation and the darkness of the artist's fate:

Already
with thee! Tender is the night....

But here there is no light,

Save what from heaven is with the breezes blown,

Through verdurous
glooms and winding mossy ways.

Byron, Shelley and Keats
all died young, unlike Wordsworth, Blake and Coleridge. The idea of passing from "this
life" early became a Romantic trope of the artist's fate, the tragic fact that would
establish his glory and cause his soul, as Shelley described the already deceased Keats, to
beacon "from the abode where the eternal are."

Admittedly the
optimism-pessimism dichotomy can be overstated, but it is a basic start in understanding how so
much changed in poetry in a relatively short period.