THAT shadow, my likeness, that goes to and fro, seeking a livelihood,
chattering, chaffering;
How often I find myself standing and looking at it where it flits;
How often I question and doubt whether that is really me;
--But in these, and among my lovers, and caroling my songs,
O I never doubt whether that is really me.

Walt Whitman

http://www.poemhunter.com/poem/that-shadow-my-likeness/