how does walt whitman present humanity in leaves of grass?

Whitman's work embodies two ideals which seem to oppose each other: the first is his notion of the self, the second is his idea of the tribal, or collective, spirit of America. Whitman sings odes to the individual, and lifts up self-discovery as the highest ideal of the individual. But the self, inconsistent on its own, must also battle with the needs of society. It is both physical and spiritual and Whitman attempts to reconcile these differences. This duality, for Whitman, is mystical and mysterious. The speaker is both the individual and the microcosm of society - he contains multitudes.

Whitman also upholds the collectivity of the nation. "Crossing Brooklyn Ferry" is, perhaps, Whitman's best example of the way humanity is connected through a common spiritual unity. This is a unity that the self seeks but that correlates to a common humanity.