For the speaker of "Song of Myself," his self and the universe are one and the same. While he articulates his own specific privileges and joys, such as being "thirty-seven years old in perfect health," he does not only celebrate himself. The speaker of this poem revels in the unity of all things, not only of his exquisite existence but of all people "born here of parents born here from parents the same, and their parents the same." He marvels at how these generations of people, including himself, are "form’d from this soil, this air."
The speaker in section I of "Song of Myself" also encourages the reader to tap into and feel the currents of joy generated by this unity of all living things. Consider the last stanza:
Creeds and schools in abeyance,
Retiring back a while sufficed at what they are, but never forgotten,
I harbor for good or bad, I permit to speak at every hazard,
Nature without check with original energy.
What is Whitman saying here? In the first two lines, the speaker acknowledges the existence and usefulness of formal knowledge, profession and education, "creeds and schools." Yet in the last two lines, he turns to something much more invigorating, much more essential. The speaker remains open to the influence of "nature without check with original energy," whether "good or bad." The speaker embraces the unpredictable, raw, and powerful forces of nature—the natural world, human instincts, and the power of one's connection with all else.
In these first four stanzas, Whitman's speaker celebrates himself, his connectivity with every other thing in the universe, and the feeling of rejuvenating "original energy" in simply being a living thing.