The speaker of "A Summer Night" walks through a deserted street, surrounded by closed windows and stillness. Looking between the roofs of the houses, he can see the moon, and beyond that, heaven.
He remembers a past experience, standing at a seashore surrounded by mountains, when the moon was constantly with him. The speaker imagines the moon asking him why he remains as restless as his past self was; his heart is neither dead nor full of passion. Rather, it fluctuates, never settling on one or the other.
In response to the moon, the speaker says that his restlessness is caused by the modern, materialistic world. He is unable to decide whether to be happy with himself or to "be/Like all the other men I see." He argues that the world is split into two types of man. The first type lives in "a brazen prison," working laboriously as their time slips away. These men are gloomy and overworked by the time death finally reaches them, having nothing to show for their efforts.
There are fewer of the second type, who are capable of escaping this prison. These men attempt to begin their lives anew, but they suffer as well from the challenges presented by their new lives. He describes this dilemma using ocean terms: they are brave sailors who unfortunately face many storms on the ocean.
The speaker questions whether or not there are lives besides these two he described, whether it is possible to be other than "madman or slave." For himself, he admires the freedom of heaven, and longs for that boundless world.
This poem offers one of Arnold's many complaints about the modern world. He clearly expresses his hatred for the way humans live, either working themselves to death or suffering because they try to break free of that mold.
The first type of man is the most common. Modernization and the rise of industries has caused unfathomable problems for these people, according to Arnold. The picture he paints - of men simply working until they die, never discovering themselves or exploiting their romantic selves, is a depressing one.
And yet equally problematic are those with the courage to break free of those constraints. In effect, Arnold is contrasting conformists with non-conformists. However, the latter type of person is doomed to be an outcast, a "Madman." He is not rewarded for his bravery, but rather tormented by it. There is a contradiction in that depiction, since the man who escapes social normality is then tormented from not being accepted by that society. As a writer and poet, Arnold clearly sees himself as being in this second category. He is the speaker, longing for the freedom and ease of heaven.
It is this contradiction which makes the speaker so restless in the first half of the poem. He has made his decision to escape the "prison" of normal life, but remains unsettled by that pretense of freedom. Ironically, he has freed himself but is still trapped by his torments. His final rhetorical question ("Is there no life, but these alone?/Madman or slave, must man be one?") does not have an answer. Instead, it implies the limitation of the physical world, where modernity has ostracized the romantic soul. As he often does, Arnold sees a release only in a greater, transcendent world, that of heaven, where dichotomies do not exist and true freedom of the individual might be possible.
This poem does not follow a set meter or rhyme scheme; there is rhyming, but the rhyme patterns vary between stanzas. Typically, poems without rigid patterns are attempting to relay the disorder going on in the speaker's mind. The speaker in "A Summer Night" believes that the world has been tainted by modernization, but at the same time he desperately hopes and dreams of some escape. It is no mistake that the moon calls him "restless" - on the contrary, that quality explains both the rhyme scheme and thematic content of the poem.