Discussed in this essay:

Purity, by Jonathan Franzen. Farrar, Straus and Giroux. 576 pages. $28.

Purity Tyler, Pip to her friends, is a recent Berkeley graduate with $130,000 in student debt. Raised by a socially isolated single mother who works as a checkout clerk in a grocery store, Pip has no connections or mentors, only a vague notion of “doing good in the world” and the ambition “not to end up like her mother.” She’s a squatter in a makeshift household of activists and Occupy sympathizers in Oakland. She barely ekes out a living at a Bay…