In one of his earlier poems, Matthew Arnold expresses his desire that humankind be saved from the troubles and toils of life. He begins by speaking solely to "thou" (you), but by the second stanza addresses a more general audience, either using "we" or speaking to an unspecified listener.
Throughout each stanza, he asks that mankind be saved from: the world's temptations; languish; lethargy; and even from human nature itself.
He also notes how certain vices - like pride - can ruin the human spirit by distracting it from God. He hopes that man will eventually be set free from troubles, so that "light [will] bring no blindness" and "love no unkindness."
The repetition of the line "from the cradle to the grave" is incredibly central to this poem. It appears in the first stanza and then as the penultimate line, underscoring its importance. The sentiment is that humans are at the mercy of their natures, simply as a result of living. Our struggles - mostly against our own vices - do not come from choices or circumstances, but rather as a result of being born, having flesh. We are unsafe from birth, and these vices will only intensify as life goes on. This idea aligns with that of original sin, which suggests that humans are born into sin and must struggle against it. Even the line's placements - at the poem's beginning and end - expresses this idea of an ever-present threat.
Throughout the poem, particularly in the final stanza, Arnold employs juxtaposition to make his point. He tends to place seemingly antithetical elements next to one another. Grief and passion, sorrow and joy, comfort and trouble, love and mistrust - it is interesting that these seem to be contradictory concepts. And yet this very contradiction is the essence of the poem. Humans are, he suggests, both drawn towards vice and yet driven towards the transcendence of purity. Our lives are marked by struggle because we want to be better than we are.
In this way, the poem does express a certain pessimism. Considering how driven towards natural beauty Arnold can be in other poems, "Desire" certainly espouses a difficult and sordid existence, one that looks critically at mankind's natural state. The title, in fact, gives a window into this concept - what dooms us is our "desire," which might evoke Buddhist thought to some readers. That tradition suggests that humans desire because they are alive, and that desire is the source of all trouble. Here, Arnold seems to echo that sentiment, that because we feel and want for ourselves, we doom our souls.
It is difficult to understand this sentiment outside of a religious context. God is quite present in the poem. Not only does he address the deity directly on several occasions, but he suggests that we should be struggling to get closer to Him. Notice the third stanza, where he suggests we are held back from God by our own vices, like pride. Further, it is possible that the "thou" of the first stanza refers to God - someone who lives alone and knows all. If one takes this interpretation as correct, then the poem is a plea, directed towards someone whom Arnold hopes can help us.
Another element that suggests the poem is a plea is the final line of each stanza, each of which is an imperative for salvation. (All but one read "Save, O, save!"). This suggests that the poem is indeed directed towards someone with greater power than man has. This underscores the pessimism of the poem. Arnold does not believe mankind can free himself from his vices; he needs the help of some other force.
Finally, it is important to note that the religious sense also suggests a certain inevitability. Again, Arnold does not direct the poem towards humans, as a warning. Instead, he seems to see our vices as almost fate-like elements which attack us despite our characters. Notice the way he personifies both "pride" and the "soul" in the second stanza. Pride swoops in and corrupts the soul with his destruction, and she (the soul) is powerless to stop it. Arnold frequently personifies intangible ideas such as these; it establishes the sense that something else has control over human nature, an actual being which exists and can manipulate the soul to its will. In the end, the poem has a rather dark and punishing undercurrent, in the suggestion that we are doomed to destroy ourselves through vice and desire unless we are saved.