"Toni Bentley has written a memoir about her three-year experience of sexual awakening via anal intercourse with a man. Like most sexual memoirists, Bentley claims our attention with the more or less tacit premise that she has transgressed custom, morality, or received opinion—in her case, by finding liberation in being in a “demeaning” submissive role in her sadomasochistic recreational affair. In order to find Bentley’s story compelling, the reader (whether neocon, ur-feminist, or third-waver) must grant that such an arrangement is somehow shocking. Given that the most likely audience for Bentley’s book veers to the left, the intended surprising counterintuition is that her “subjugation” through anal sex was satisfying for her. She did not turn the tables of paternalism with a large purple strap-on. But is there any way—scientifically, we mean—to prove that anal sex is unfair to women? We speak of equal opportunity. Let us examine a woman’s opportunities for penetration."