The psychoanalytic lens is when you look at the characters individually on a personal level. You look at the state of mind of the characters, their emotions, and how they feel about life by reading in between the text.
"I am still a little afraid of missing something if I forget that, as my father snobbishly suggested,...A sense of the fundamental decencies is parceled out in equally at birth" (p. 2)
He has sets up his philosophy throughout the whole book by basically saying