From A Backward Glance:

Let me not dare, here or anywhere, for my own purposes, or any purposes, to attempt the definition of poetry, nor answer the question what it is. Like Religion, Love, Nature, while those terms are indispensable, and we all give a sufficiently accurate meaning to them, in my opinion no definition that has ever been made sufficiently encloses the name Poetry; nor can any rule of convention ever so absolutely obtain but some great exception may arise and disregard and overturn it....


From Leaves of Grass:

 

As I Lay With My Head In Your Lap Camerado

As I lay with my head in your lap camerado,
The confession I made I resume, what I said
to you and the
    open air I resume,
I know I am restless and make others so,
I know my words are weapons full of danger,
full of death,
For I confront peace, security, and all
the settled laws, to
    unsettle them,
I am more resolute because all have
denied me than I could
    ever have been had all accepted me,
I heed not and have never heeded either experience,
    cautions, majorities, nor ridicule,
And the threat of what is call'd hell is
little or nothing to me,
And the lure of what is call'd heaven
is little or nothing
    to me;
Dear camerado! I confess I have urged
you onward with
    me, and still urge you, without the
    least idea what is our destination,
Or whether we shall be victorious, or
utterly quell'd and
    defeated.

 

Books by Whitman at Powell's Books