Then one Saturday morning, two weeks after he moved out of Rachel’s place, Toby woke up and realized he was alone. His new apartment seemed like a set in a depressing play, bare and filled so sparsely with objects…simply to fill space.
-- Narration (chapter 1)

Importance: After Toby and Rachel separate, Toby has freedom to explore new relationships. However, despite the fact that he goes on many dates, none of the dates ever evolve into deep, consistent relationships. The above quotation describes the emptiness and loneliness of Toby's apartment, which parallels his sense of painful loneliness following the separation.

You have to look these people in the eye. This isn’t organs. This is people.
-- Toby (chapter 1)

Importance: After unconscious Karen Cooper is admitted to the hospital, and after Toby reaches a diagnosis, Toby and two other doctors confer with Karen's husband. Toby alter scolds the two younger doctors for being cold and detached when...