Whitman's "O Me! O Life!" is a poem of contrasts and, ultimately, a statement about the humble but irrepressible value of life.
The poem presents the first stanza as a question, which essentially asks how an individual can see his life in a meaningful light when one is drawn back recurrently to thoughts of how "foolish" and "faithless" human beings are. The narrator includes himself among the ranks of the foolish and faithless and suggests that all people are interconnected in a web of "sad [...] recurring" "empty and useless years."
The second, brief stanza of the poem offers a concise rebuttal to the distress and angst of the first stanza. "What is the value of a life?" the first stanza asks.
The value of a human life is that "you are here - that life exists and identity." Every individual has an opportunity to live, however sordid or recurrently lost he may be in his life, and as the collective life of mankind goes on every individual "may contribute a verse" to the larger story that is mankind.
What is the universal theme then? Life is its own value, its own prize and explanation.