Before Dr. Kinsey's 1947 study of human sexuality, people thought masturbation blinded people, that gay sex was rare, and that the missionary position was the only one widely used. In fact, almost everybody masturbates, a third of men have gay sex, and couples try many positions. Kinsey's critics controvert his methods and statistics, but recent studies confirm his findings, whose impact is huge - gay sex was decriminalized as a result.

A man brilliant at human studies but with no insight into human nature, Kinsey here is unaware of hurting feelings, of offending people, making enemies, and that his tunnel vision limits his image, family, associates, and even his funding. He first collects and studies a million gall wasps; switching to human sex, he views people with detachment, putting them at ease in interviews.

Kinsey begins sex research by accident; a young couple ask advice. Kinsey and Clara (Linney) were virgins in their 20s on their wedding night. Sexual thinking was limited to Ideal Marriage: Its Physiology and Technique, by van de Velde, advice too cautious to help. Kinsey's bestseller gives him renown, but Congressional witch-hunters target it. Convinced his ideas are communistic, a committee pressures the Rockefeller Foundation to withdraw funds.

Kinsey encourages his staff to record their findings after sex with each other; spurning secrets, he makes his wife cry by telling her he's had gay sex. Clara is as warm as her husband is heedless: she loves and understands him, and is his buffer. Kinsey sleeps little, drives himself, alienates colleagues, and falls ill from barbiturates, but continues discoveries. For one, people aren't gay or straight, but between 0 and 6 on a straight-to-gay scale. He's about a three, he says. When he interviews his strict father (Lithgow) about his sex life, he learns why the man is so bitter. In all, Kinsey is more interested in what people do than why.

"Kinsey" parallels "A Beautiful Mind" (2001); both men are brilliant in narrow channels. "Kinsey" captures political and moral fear and repression. A University of Illinois professor lost his job in 19959 for suggesting students consider sleeping with each other before marriage. Universities now give advice on safe sex and contraception, and still face opposition, but the difference is that Kinsey redefined what we call normal sexual behavior.