Sexual Perversity in Chicago.

-Mamet, David Alan
  Title of play.

Perversity is the muse of modern literature.

-Sontag, Susan
  Against Interpretation,'Camus' Notebooks'.

They who do not understand that a man may be brought to hope that which of all things is the most grievous to him, have not observed with sufficient closeness the perversity of the human mind.

-Trollope, Anthony
  OfTrevelyan's paranoia about his wife's fidelity. HeKnew He Was Right, ch.38.