While a biology professor at Indiana University, Dr. Alfred Kinsey pioneered the connection between science and sexuality with the results of a series of coded questionnaires about sex habits.

It seems like a no-brainer that similarly conducted surveys today would suffer the same negative moral-majority knee-jerk as they did in 1948, when Kinsey published Sexual Behavior in the Human Male.

In Kinsey, writer-director Bill Condon (Gods and Monsters) generates as much engaging material from his subject’s anti-establishment stance as he does in the unexpectedly moving character study. Pulling it off mostly with subtlety is a technique rarely seen in such films.

Of the numerous biographies with daddy-didn’t-love-me scenarios, none generates a theme as subtly fierce as this one. As the totalitarian Kinsey patriarch, John Lithgow’s brief turn echoes through the entire film, his traits showing up in Alfred later in life.

The most crucial component of why Kinsey works is Liam Neeson, taking a role that seems tailor-made for a resident oddball like Johnny Depp and making it his strongest part in a decade.

Aside from masterfully showing his father’s influence for better or worse, Neeson makes the egghead endearing, from mere physical appearance (that woefully unstylish hair) to academic smarts. (The unquenchable thirst for scientific statistics hasn’t been this entertaining since A Beautiful Mind.)

Neeson’s performance is so enthralling that almost everyone else with a featured role in the all-star cast (OK, at least by indie-film standards) must settle for revolving around him. Laura Linney fares well as Kinsey’s wife (a marriage forged more by friendly connection than furious passion).

But Peter Sarsgaard mixed danger and niceness better in Garden State, here showing up as a Kinsey researcher and part-time lover and surrogate son for both the Kinseys. Tim Curry, Oliver Platt and Dylan Baker — all capable of far more — are recognizable-face window dressing.

Condon reserves his best moments for the bit players, Lithgow among them. If Judi Dench can get an Oscar nomination for her brief turn in Shakespeare in Love, so can Lynn Redgrave for her divine work here. Her unnamed interview subject condenses her sad life story into a five-minute scene with great grace and composure.

And William Sadler, as the very definition of a sexual predator, is a true menace precisely because he seems so nonchalant about his actions.

It’s through his character that the film is unable to sustain its greatness, sidetracking a smart look at how far the detachment of Kinsey and crew can go in the face of detestable acts. The movie makes no apology for Sadler’s deeds, but it certainly doesn’t make much of them, either.

Instead, it offers up a retread riff that all you need is love, flying in the face of the previously inventive material before. Had the Kinsey marriage seemed founded on anything other than a casual respect for one another, this rekindling of emotion might have worked more strongly.

Kinsey is set in the past, but its skewering of Puritanical piety packs a present-day punch. We are, after all, the country that got into a tizzy over a nanosecond flash of Janet Jackson’s nipple.