What is the meaning of the line "I do not ask the wounded person how he feels, I myself become the wounded person" from Walt Whitman's "Song of...

This amazing insight from Walt Whitman is an encapsulation of his philosophy – that we are not so much individuals as “leaves of grass”; superficially we appear to be individual, unique beings, but in a larger sense, we are each part of the whole, and we share the condition of being “human” – we are "each other" in the larger, cosmic sense.  Here, he differentiates between empathizing the pain of another, and actually “sharing the experience” itself.  It is difficult to paraphrase this difference in words more succinct, more viable, than Whitman’s own.  Whitman’s ability to empathize goes beyond mere imagining what an experience might be to another – he negates the, to his mind, separateness of individuality, and steps, not “into the shoes” of the wounded person, but into the wholeness that is the human species.  His experiences in the Civil War gave him this anguished and anguishing insight.