The tone of "Dover Beach" is calm and melancholy at the beginning of the poem. The speaker is with his beloved, looking out of the window at the calm sea and asking her to be true to him. This, however, is far from a conventionally romantic moment. The reason the speaker gives for the importance of their relationship is simply that nothing and no one else cares for them. They are like frightened children, facing an indifferent universe and clinging to one another out of fear as well as love.
The poem rises at the end to a crescendo of despair as the speaker concludes that
the world, which seemsTo lie before us like a land of dreams,So various, so beautiful, so new,Hath really neither joy, nor love, nor light,Nor certitude, nor peace, nor help for pain.
The nihilistic, despairing tone at the end of the poem is caused by the decline of religious faith throughout the world and in the speaker's own heart and mind, symbolized by the "melancholy, long withdrawing roar" of the "Sea of Faith." The speaker acknowledges the widespread waning of the idea of a personal God who cares for humanity and gives purpose and meaning to life. The world, he acknowledges, looks beautiful, but it has no heart. The poem is a response to what scholar Julie Melnyk calls the "Victorian religious unsettlement," in which various scientific, political, and philosophical movements combined to create a decline in religious belief among educated Victorians.