These, and all else, were to me the same as they are to you, I project myself a moment to tell you – also I return. (lines 50-51)
What's going on? Does the speaker have a split personality, or the power to be two places in once? We think he just doesn't make a distinction between his real self and his literary self. The voice we hear in our head when we read "Crossing Brooklyn Ferry" is the real Walt Whitman, just as much as the flesh-and-blood man. Or at least that's what he wants us to think as we read the poem.
I too had received identity by my body, That I was, I knew was of my body – and what I should be, I knew I should be of my body. (lines 60-61)
Whitman chooses his words carefully: what does it meant to "receive" one's identity? Somehow the speaker understands himself by observing and living within his own body. Unlike philosophers and theologians who believed in a "ghost in the machine" – a strict division between body and soul – the speaker thinks the soul takes its cues from the body. He feels neither shame nor dissatisfaction with his body.
It is not upon you alone the dark patches fall, The dark threw patches down upon me also, (lines 68-69)
His identity includes the "dark patches" or evil thoughts. Everyone, he says, is made up of this combination of light and darkness, good and evil. You can't separate the two from one another; for example, by saying that one is "innocence" and the other "guilty."
The wolf, the snake, the hog, not wanting in me, The cheating look, the frivolous word, the adulterous wish, not wanting, Refusals, hates, postponements, meanness, laziness, none of these wanting. (lines 78-80)
The speaker has a veritable jungle inside him. He's part-man, part-wolf/snake/hog. Once again, his choice of words is interesting. He says his evil thoughts and actions are "not wanting," or lacking, as if it would be a problem if they were lacking. His "dark patches" make him a complete person.
But I was a Manhattanese, free, friendly, and proud I was called by my nighest name by clear loud voices of young men as they saw me approaching or passing, (lines 81-82)
By calling himself "Manhattanese," the speaker connects his identity to the Native Americans who originally inhabited the island. A lot of people think of Whitman as a nature poet, someone who hangs out in the grass all day. But, at heart, he's a city slicker: a big, brash New Yorker.
Played the part that still looks back on the actor or actress, The same old role, the role that is what we make it, as great as we like, Or as small as we like, or both great and small. (lines 86-88)
The speaker suggests that the roles we play in public are more real than our private thoughts. Whitman seems to follow Ralph Waldo Emerson's philosophy of "self-reliance' in saying that our public roles are whatever we make of them. We can be Hamlet, Polonius, or the guy who serves the drinks: the choice is ours.
Through you color, form, location, sublimity, ideality, Through you every proof, comparison, and all the suggestions and determinations of ourselves. (lines 139-140)
At the end of the poem, he says that our identity is like a mosaic of things grand and small. We are "determined' by our environments and the things we encounter in the world. We're not just a bunch of pre-made souls that plow through the world without begin changed by it. A simple point, maybe, but a profound one.