What are the themes in "Frederiksted, Dusk" by Derek Walcott?

To find the themes of "Frederiksted, Dusk" by Derek
Walcott, let's start with trying to sort out the meaning of this complicated poem. It is
a kind of transcendental poem that addresses the transcendence of life over death by a
poetical examination of objectified life experiences (e.g., staring at sunset; tanning
on a rock) and by philosophically reflecting on that which has been objectified, thus
transcending (rising above) objectifications.

The poem
starts out like a narrative with perhaps the commonest of all sorts of people as the
protagonists, old men "set down ... outside the almshouse," or the poor house. The
narrative-like current of the poem goes on to compare the old men's "level stare of
light" to a "girl tanning on a rock" who "fills with light," connecting them again
further down the poem with references back to the light-filled, youthful girl: "would
shine in them"; "substantial light and insubstantial
stone."

The transcendent process begins right at the start
of the poem in the opening metaphor and simile Walcott employs: sunset is a picture
show; old men are like empty bottles set down in the morning (like empty milk bottles
set out to be picked up). Walcott then launches a series of completely impossible
figures of speech, a trope called
catachresis: "the rising evening brim
their eyes"; "level stare of light"; "more than mortality brightened air"; a girl who
"fills with light."

The narrative fades out after the girl
full of light on the rock and the focus changes to philosophical musings on "Whatever it
is / that leaves bright flesh like sand," thus transcending the objectified narrative.
The main topic is death ("leaves ... flesh ... and turns it chill"), but it is death
with an incongruous twist examining the complex realities between the "simplicities" of
"life and death."

This "Whatever it is" is a "state," a
"collective will," that shines--like the light that fills the girl--in the dying old
men. The "state" waited ("a state ... and it waited") like the girl also waited ("it
waited too") in the incongruity of
substantial  light and insubstantial
stone. The message derived from the poem is that human inner being, inner
light, transcends over both the substantially real misfortune of being set out like an
empty bottle in front of almshouse and the equally substantially real rock to lay and
tan on.

The themes now emerge
a little more clearly. The major theme is as stated before, that being the transcendence
of life over death. Another is the transcendence of humanity's inner light over
objectified reality. Another is the shared resource and essence of light: the sunset and
the old men shared a stare because they share essential light, one source of the shared
light being the Sun, the other source the inner being of
humanity.