At the earliest ending of winter,
In March, a scrawny cry from outside
Seemed like a sound in his mind.
He knew that he heard it,
A bird's cry, at daylight or before,
In the early March wind.
The sun was rising at six,
No longer a battered panache above snow...
It would have been outside.
It was not from the vast ventriloquism
Of sleep's faded papier-mache...
The sun was coming from the outside.
That scrawny cry--It was
A chorister whose c preceded the choir.
It was part of the colossal sun,
Here the poet emphasizes that this comedic renewal is exogenous to himself – it must be the case, because it does not depend on the poet’s mind for animation. This is a reassuring thought to him, almost like a religion. 
 (Source:   Open Yale Courses.  )
Not Ideas About the Thing but the Thing Itself