If you’ve sat through a freshman-level science-and-religion class, you’ve heard most of what passes for argument about evolution vs. creation in Darwin in Malibu. But that’s OK: When it’s not recapping that tired old squabble, it’s a sturdy-enough little meditation on living in the shadow of mortality, a debate dressed up with just enough of the fantastical to keep an audience engaged in other questions that can’t really be settled.

It goes down pretty easy, too, in Steven Carpenter’s modest staging for the Washington Stage Guild, not least because of the considerable pleasures of Leo Erickson’s droll, laconic Darwin. That worthy, when the lights come up, is ensconced in a deck chair at an oceanfront residence in the California town of the title—and yes, the facts of the play’s geography (fault lines, anyone?) will turn out to be an important theme rumbling underneath playwright Crispin Whittell’s metaphorical jousting.

Darwin’s only companion in the early going is a young woman (Alejandra Escalante) with whom he seems only newly familiar; she makes him banana smoothies, listens to his gentle interrogations about a boy who seems perhaps to have broken her heart, and forgets to mention the man who’s waiting at the front door to talk to the author of The Origin of Species. This of course will be Thomas Huxley (Robert Leembruggen), Darwin’s great champion, dead 100 years and more—I did mention it’s a fantasy, yes?—and he’ll be followed hard by Samuel Wilberforce (Jeff Baker), the Oxford bishop at whom Huxley famously lobbed snark in an 1860 debate.

It takes a bit more setup than you might hope (42 minutes’ worth, by my count, including a bluntly expositional section that might as well be prefaced by a title card saying “Let Us Tell You Who We Are, If You’ve Forgotten”), but once the forces are all assembled, Wilberforce announces that they’re all trapped in some sort of purgatory, and he’s there to Bring Darwin to God. Certain rhetorical festivities, it will not surprise you to learn, then commence.

Leembruggen contributes a pretty delicious slow burn during one particular conversation about the logistics of ark-building; Baker turns in a bishop whose stoic defense of his faith seems rooted less in a careful theology than in a patrician sense of entitlement about how things ought to run; and Erickson’s Darwin observes it all, bemused, lobbing in the occasional dry one-liner and generally creating the sense that he’s the sort of man who’s content not to have all the answers. And as a trio of books—Darwin’s opus, the Bible, a soapy romance novel—become lenses through which the men begin to see their old familiar worldviews a little differently, a sea breeze blows in to scatter and mingle the pages of all three.

With that melancholy, ambiguous final gesture, the play confronts the audience with the notion that we all live in a kind of purgatory: unable to unknow what we know courtesy of Darwin and his scientific heirs, conscious that we’ll never really discover all the facts about the clockwork of our ever-expanding universe, grasping about in the growing darkness of our approaching end, hoping to get our hands on some larger truth that’ll make sense of the facts at our command.

Washington Stage Guild’s Darwin in Malibu runs to Nov. 21 at the Undercroft Theatre.