“Contrary to what these women seemed to think,” Waldman writes of Nathaniel P.’s flings and semi-steady girlfriends, “he was not indifferent to their unhappiness. And yet he seemed, in spite of himself, to provoke it.”

He provokes it by taking advantage of a social landscape in which sex has been decoupled from marriage but biology hasn’t been abolished, which means women still operate on a shorter time horizon for crucial life choices — marriage, kids — than do men. In this landscape, what Nate wants — sex, and the validation that comes with being wanted — he reliably gets. But what his lovers want, increasingly, as their cohort grows older — a more permanent commitment — he can afford to persistently withhold, feeling guilty but not that guilty about doing so.

Waldman’s portrait of Nate’s romantic life is sympathetic enough to have earned her fan mail from young men. But it’s precisely because Nate is sympathetic rather than toxic that the “Nathaniel P.” phenomenon — or what Rebecca Traister has dubbed “the scourge of indecisive men” — is a hard problem to escape. Indeed, it seems like one of the hidden taproots of well-educated women’s work-life-balance angst, and one of the plausible explanations for declining female happiness in a world of expanded female opportunity.

And lurking in Waldman’s novel, as in many portraits of the dating scene (ahem, Lena Dunham, ahem), is a kind of moral traditionalism that dare not speak its name — or that can be spoken of only in half-jest, as when the novelist Benjamin Kunkel told Traister that the solution was “some sort of a sexual strike against just such men.”

Because Kunkel is right: One obvious solution to the Nathaniel P. problem is a romantic culture in which more is required of young men before the women in their lives will sleep with them.

To the extent that parents tend to see the next generation’s world through their children’s eyes, that’s an insight that’s more immediately available through daughters than through sons.

And no matter what the next study says about your likelihood of actually turning into a Republican, once you’ve flirted with that insight, you’ve tiptoed a little closer to something that might be described as social conservatism.

Even if you live in Brooklyn.