What is the theme of "Dover Beach" by Matthew Arnold?

Central to understanding this poem is recognising that
through it Arnold is lamenting the loss of faith or culture in his society and painting
a picture of a world that, as a result of this loss of faith, is full of cruelty,
uncertainty and violence.

Note how the sea imagery develops
this theme. Reference to the "Sea of Faith" and its gradual withdrawal from the coast
indicates that Arnold considers its loss is a negative
occurrence:

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The Sea of
Faith

Was once, too, at the full, and round earth's
shore

Lay like the folds of a bright girdle
furled.

But now I only
hear

Its melancholy, long, withdrawing
roar...

Note how the sound
the Sea of Faith makes as it withdraws is described as "melancholy" and that as it
leaves it exposes the "naked shingles of the world," leaving the world exposed,
vulnerable and open to wounding.

The final stanza describes
Arnold's view of this new world that is marked by its absence of Faith. This world,
although it may appear to be "like a land of dreams," actually is not. Instead
it:

Hath
really neither joy, nor love, nor light,

Nor certitude, nor
peace, nor help for
pain...

As a result, Arnold
imagines that he and his beloved are on a "darkling plain" only listening to the sounds
of "ignorant armies" clashing by night. In such a world, love is the only consolation
that can be found, and therefore, the speaker urges his lover and himself to "be true to
one another."