The Heart Is A Lonely Hunter - Part III

As the novel closes, Biff felt "he was suspended between radiance and darkness.  Between bitter irony and faith.  Sharply he turned away" (McCullers 359).  What is McCullers purpose or rather what is McCullers saying about Biff or even all the other characters in this line? 
Look at each of the four chapters of Part III where each of the four visitors of Singer are described.  Mick, for instance, seems to be stagnant--she admits that "some good" was left in her, but "no music was in her mind" (353-354).  Then Jack who participates in a fight, "the dead were Jimmy Macy and Lancy Davis" (346).  He seems angry, haunted with "the old terror that always came as he awakened" from nightmares, but at the same time he feels "there was hope in him" (350).  How can that be?  And of course Dr. Copeland, who is off to Grandpapa's senses "the fire in him and could not be stilled"...there is radiance, but darkness as well (336).  He felt right at the beginning of the chapter that "neither truth nor purpose [were] in his thoughts" (329).  These are just some of the instances where I see these characters living in between 'radiance and darkness'.  Were they living this way from the start of the novel, did Singer's death exasperate their pain, or help them to move forward in their lives?

Part Two Question

After reading section two, one thing that I have noticed is McCuller's deliberate use of light and dark. For each character, darkness and lightness represents a different feeling-whether it be uneasiness or the fact that they feel most at one with themselves in either the dark or the light. After tracing the use of dark and light in each character's section, ask yourself these questions: How does darkness verse lightness display the characters' feelings of isolation and those of solitude. How does lightness reveal something about the characters? How does darkness? Why does McCuller's purposely use light and dark to reveal certain aspects of her characters? How does this enhance the feeling of isolation?

Feel free to talk about any character, or multiple characters if need be.

Some pages in part two where darkness and lightness come up are:

pg. 101, 111, 119, 138, 143, 178, 181, 203, 213 etc.

There are many other references, seeing as this is quite a long part, however, here are just a few to get you started with the idea.