“The Hard Problem” is Tom Stoppard’s first work for the stage since 2006’s fantastic “Rock ‘n’ Roll,” and like “Rock ‘n’ Roll,” it asks whether there’s such a thing as a soul, or whether a human being is just “a pinball machine which thinks it’s in love.”

But where the earlier play offered a clash between Marxist materialism and the pagan ecstasy of rock music, “The Hard Problem” is a more blunt and programmatic conflict between evolutionary biology and a sort of heavily diluted Christianity, set in a brain-science research institute.

I saw National Theatre‘s broadcast production from London to international movie theaters, which closes May 27. “The Hard Problem” is short—only 100 minutes—and it feels undercooked compared to Stoppard’s other work. The problems and stakes are often stated too explicitly, and only one of the characters is fully fleshed-out.

That character is Hilary (Olivia Vinall), a young psychology researcher whom we meet as she’s using the Prisoner’s Dilemma to flirt with her tutor, Spike (a suitably greasy Damien Molony). Hilary argues that the abstractions of the Dilemma leave out everything that real-life arrestees would know about one another. “I’m gonna give Bob a chance to go straight!” she declares: she’ll hang tough, regardless of whether her fellow prisoner sings. And when her tutor asks why, she says, with just the right mix of irony and sincerity, “Because I’m good!

Spike replies, “Don’t say the word ‘good’ as if it meant something in evolutionary science.”

Hilary is good, we learn. (This is one of the very few artworks in which I can actually believe it when other characters praise the virtues of the hero.) She’s also something more than that: Spike comes out of a postcoital shower to find her kneeling by the bed they’ve shared, praying.

The rest of the play explores what Hilary thinks she’s doing when she prays, and whether it can fit into a scientific worldview. The conflict is over-simplified, in part because Hilary herself doesn’t seem sure whether she’s arguing for “God” as a Platonic Form—an “overall moral intelligence” that grounds human morality and allows us to distinguish “good” from “beneficial for species survival”—or whether she’s arguing for “God” as an active and loving Person.

But maybe that’s the point. “The Hard Problem” may be one of those works in which the surface question isn’t the real question. The surface question is: Does the inability of the sciences to explain consciousness and morality leave God “the last man standing”? Hilary makes the case most briefly when she says, “I agree with you, Spike. Morality isn’t scientific. So there must be something else, which isn’t science.”

But Hilary’s own life suggests that people don’t long for God the Explanation. When Hilary prays, what she says is: forgive me; protect those I love; thank you. Even as she argues that “When you get to [explaining] consciousness God pushes itself to the front of the crowd like a doctor at the site of an accident” her choice of metaphor suggests that she’s not really thinking about the philosophy of mind, but something more personal.

She’s the only character who does pray, the only one who considers prayer something more than nursery rhymes. Stoppard gets a lot of easy mileage out of the English discomfort with religious faith: “So you, as it were, pray to God, then?”

Hilary is a moving character, simultaneously brash and humble, whose arc within the play is poignant and satisfying. Vinall is a joy to watch, whether she’s challenging the materialist men who surround Hilary, or struggling to explain the source of her sorrow. Parth Thakerar, as an overconfident materialist who suffers a serious setback at work, is a scene-stealer, fierce and funny. His ecstatic little “but!” as he announces a market crash pops like a champagne cork: Everything’s good news for somebody. The National Theatre production is appropriately spare: strings of lights, beautiful and evocative of neural pathways, serve as backdrops.

There are other threads here: the unpredictability of the market as a mirror for the unanswerable questions of philosophy; children’s innocence versus their responsibility; the mentor/protégée relationship as a mirror for parent/child relationships.

It’s an eroticized mirror, though: All the mentoring relationships in this play are sexualized on at least one side. Sexuality is the only language these characters seem to have with which to work out their neediness, intellectual excitement, guilt, admiration—everything that could link them to other adults.

On a theoretical level this might sound like a good idea: Just as Spike reduces human motivation and morality to physical survival, so these characters (and/or the culture that shaped them) reduce all their longings and emotions to sexual attraction. But as an actual thing that happens in a real play that you watch, it’s slightly baffling and boring. One man openly says that he only understood another character’s motivations once he was informed that she was acting out of a lesbian crush, as if all other human motives have become utterly unintelligible to us. I know Stoppard knows how to write sublimation, so I’m assuming this was deliberate cultural critique.

This is not Stoppard’s best work, nor even his best work on these topics, but it’s well worth your time. There are good lines and sharp insights—and there’s Hilary, with her gentleness born of guilt and grief. Still, there’s too much “debate on stage” and too little character development—too little of “Rock ‘n’ Roll”‘s weirdnesses, ecstasies, and sudden sorrows.

For a play about the unpredictability of human action, “The Hard Problem” feels too planned.

Eve Tushnet is a TAC contributing editor, blogs at Patheos.com, and is the author of the recently-released book Gay and Catholic: Accepting My Sexuality, Finding Community, Living My Faith.