In Faulkner's As I Lay Dying, what is the meaning of Darl's thinking about sleep and being and not being? How is this Faulkner-esque? What is...

Darl is the most perceptive and intuitive of the novel's
narrators, and the reader hears his voice more than any other character.  The other
characters are in some way limited in their narrations (Jewel is angry: Vardaman is
young; Dewey Dell is consumed with her pregnancy; Cash is overly regulated and
practical), so any sense of sensory perception most likely comes from
Darl.

Faulkner's stream of consciousness technique is
highly illustrated in Darl's sections as his mind wanders between his own internal
reality and the external reality in which he is forced to participate.  In many cases,
Darl is able to comment on more than one reality at a
time. 

In this particular scene, his notion of sleep  gives
the reader a true impression of his highly intuitive and perceptive nature.  Sleep to
Darl is not simply a rest from work, but an escape from a reality that he is seeing as
increasingly comical.  He is also exploring his own sense of being which is juxtaposed
to Vardaman's confusion of death, Jewel's status as a family outcast, and Dewey Dell's
new being growing inside of her.  To Darl, being alive is much more than farm duties. 
He senses nature and others. 

Oftentimes, as is common with
this narrative style, Darl is confusing.  His discussion about being emptied for sleep
ends with the line "And so if I am not emptied yet, I am is."  Here
Darl is struggling with two senses of selves:  Darl as a son and brother, and Darl as an
amorphous concept. In addition to dealing with the death of his mother in the moment,
 Darl is constantly searching for this concept, and it is this search that contributes
to his insanity.