Matt Walsh has a simple question — but he sure has trouble getting a straight answer.

Walsh is the blogger whose hard-line conservatism has, over the years, garnered much hate and even some death threats. Having recently joined Ben Shapiro’s “Daily Wire” — which according to Wikipedia, is the second-most-popular publisher on Facebook — Walsh has completed his first full-length documentary, plainly but provocatively titled “What Is a Woman?”

In it, the iconoclastic writer does little more than interview a range of people on the titular question — along with other hard-hitting queries about biology, gender, and sex reassignment.

I don’t need to tell you that viewers’ take on gender identity will largely determine how they react to Walsh’s film. It certainly determined how his subjects responded.

Walsh questioned a pediatrician, a psychologist, a surgeon, a professor, a transgender man, a couple of authors, more than one teacher, a “gender-affirming therapist,” an aging blue-collar shop-owner, a slew of sign-carrying protestors, high school and college athletes, and a Canadian father who’d been jailed for trying to prevent his 13-year-old daughter from getting court-ordered cross-sex hormones.

With a few exceptions, answers Walsh got run along the lines of “A woman is someone who identifies as a woman.” When he pushes for something more specific and less circular, many subjects dig in — such as, for example, the college prof who says Walsh’s professed aim of “getting to the truth” sounds “transphobic, condescending and rude.”

The blogger’s interviews took him to Boston, Hollywood, Times Square, Toronto, Connecticut, Washington State, San Francisco, Vancouver, and even Nairobi, where he discusses gender with the colorful and friendly Masai people. Predictably, these down-to-earth Kenyans react with amused disbelief to Americans’ insistence that a man can be a woman and vice versa.

Walsh’s most poignant interview is with Scott Newgent, who started life as a woman and transitioned to a man — but now regrets it. He spends most of his screen time with tears in his eyes, begging society not to promote radical physical changes for uncertain adolescent girls. With hard facts to support his pleas, Newgent points out that these procedures often have untold complications and can be followed by even more severely suicidal tendencies than the person had beforehand.

Sadly, these kinds of facts are absent from much of Walsh’s film, which occasionally feels almost as subjective as the folks he interviews. His ending is a case in point.

A final “definition” provided by his spouse and followed by a classic wife-request; it is — like many other moments in the film — quite amusing; but it does not serve him well as a clear-cut rejoinder to what has gone before.

Nonetheless, Walsh’s wide-ranging conversations constitute a real eye-opener — and a sharp dissection of medical and academic befuddlement.