Whitman returns to the idea that nature contains all truth. Now he talks about truth being "born" from things, having impregnated the world in the previous sections.
Truth must be shown, he says, not proven. Deep truths should be self-evident.
The "soggy clods" of damp earth will become "lovers and lamps," that is, people whose love shines within them.
He seems to be comparing people with plants that grow from the soil and spread their branches and leaves outward.