How is "Dover Beach" by Matthew Arnold a dramatic monologue?
A dramatic monologue is one that gives us an insight into the speaker's thoughts. Dover Beach is an extended meditation by Arnold on the status of religion in mid-Victorian society, but his thoughts are fragmented, diffuse, and not altogether coherent. This places Arnold's thoughts, though expressed in poetic language, on the same level as our own. When most people think, they don't do so in neat, polished sentences, and Arnold is no different.
Arnold's ruminations are also brought down to earth by their close connection to his immediate natural environment: in this case, a shingle beach at night. It's instructive that Arnold chooses to express his thoughts not through a traditional poetic structure but by using an experimental form. It's as if he's floating a potentially dangerous idea, one with truly alarming repercussions, which the usual rhythms, rhymes, and stanzaic forms of classical poetry are inadequate to contain.
Arnold's use of dramatic monologue represents a complete symbiosis of form and substance. This means that the experimental nature of the poem's construction is directly reflected in the air of uncertainty and apprehension conveyed by the lyrics. The light, both natural and artificial, has gone out, leaving us shrouded in darkness. At the start of the poem, the moon provided us with solace, but it no longer does so. Now nature is no more a source of beauty, but a metaphor for a darkening world from which the old uncertainties of the Christian faith are slowly retreating.
Arnold's gloomy prognosis hints at profound implications for poetry too. Perhaps poetry in its more traditional forms is no longer able to give voice to modern man's inner voice, a voice increasingly skeptical and uncertain. As the subject of the poem changes so too must its means of expression. After Dover Beach, dramatic monologue in English language poetry was destined never to be the same again.
Matthew Arnold's "Dover Beach" is a dramatic monologue because the poet is addressing a silent audience. The effect is of one person directly addressing another, while the reader listens in. For example, tradition has it that Arnold composed "Dover Beach" during his honeymoon, and that the silent audience is his bride. This differentiates the dramatic monologue from the soliloquy, in which the speaker only addresses himself. Hamlet, for instance, when brooding about suicide, does so before an audience, but really he is alone with his thoughts. Arnold writes, "Listen! you hear the grating roar," etc., and by this and other means implies that he is not alone, and is passionately unburdening himself to another party.
I would agree with you. The poem is certainly a monologue, but not really a dramatic monologue, since it lacks the element of a speaker distinct from the author. But this is all in the definition, since some people don't regard the distinct speaker as part of the definition of a dramatic monologue. Terms in literary criticism don't necessarily have the precise and agreed meaning that terms in biology or math do.