As I ponder'd in silence,
Returning upon my poems, considering, lingering long,
A Phantom arose before me with distrustful aspect,
Terrible in beauty, age, and power,
The genius of poets of old lands,
As to me directing like flame its eyes,
With finger pointing to many immortal songs,
And menacing voice, What singest thou? it said,
Know'st thou not there is but one theme for ever-enduring bards?
And that is the theme of War, the fortune of battles,
The making of perfect soldiers.
Be it so, then I answer'd,
I too haughty Shade also sing war, and a longer and greater one than any,
Waged in my book with varying fortune, with flight, advance
 and retreat, victory deferr'd and wavering,
(Yet methinks certain, or as good as certain, at the last,) the
These lines are decisive because the speaker is saying that he is ready to write the greater poem of the Modern Age; inspired by older poets but written with a modern perspective. 
 Indeed “Leaves of Grass” is innovative and revolutionary in style and content. In terms of content, Whitman addresses humankind in its common simplicity. By representing and celebrating everything in its real form, the speaker gives us the possibility to appreciate what is around us in a concrete way—overcoming the ideas and the spirituality of the traditional American Transcendentalism. 
 In terms of style, Whitman uses  free-verse  to free poetry of the constraints of metrical tradition and to represent all the different things with their different rhythms. 
 The Phantom (line 3) has become a Shade that is no more scary and less menacing than the first one.
As I Ponderd in Silence