Ah, and this is the trouble with a diary. We are allowed to stand too long before its mirror and gaze at ourselves, where we unavoidably find vanity and fault.
-- Sophie (Part 1: Section 2 paragraph 3)

Importance: This quote deals with one of the novel's motifs; flawed humanity. Whether people have good intentions or not, they often still do the wrong thing. In a diary, people share their secrets, thoughts, and emotions and often display their true selves. Therefore, a diary reflects both the good and bad things about human nature, and when people look back on what they wrote, they see their shortcomings. Since Sophie is writing her sincere thoughts, she is realizing her own flaws that she may not have recognized without writing it.

Why, in our efforts to understand and observe life, must we so often snuff it out?
-- Sophie (Part 1: Section 3 paragraph 4)

Importance: Though Sophie asks this question in response to science and its "partnership with the macabre...