“The Lonesome West,” written in 1997 by Martin McDonagh, is a tremendous play for many reasons, not the least of which is that it realizes the full dramatic potential of the Irish potato chip.

In the smallest of objects, McDonagh finds a world of theatrical possibilities. Taytos are the cause of much bickering, vein popping, head bopping, and general roughhousing between Valene and Coleman Connor, a pair of contentious twenty-something brothers living in the hamlet of Leenane, Ireland. In turn, the crisps are treated like religious relics, hostages and hand grenades. They are manipulated to build dramatic tension, explode for comedic release, and, consequently, crunch under the Connor’s footsteps as an ever-present subtext of disagreement and violence in the play’s final scenes. More than anything else, the crisps reveal Valene’s miserliness and his extreme territoriality, as well as Coleman’s insecurities and bottomless capacity for rage. Taytos create a rift between brothers and, later, are a stepping stone on their path toward reconciliation.

All this from a thin, tasty morsel.

Imagine, then, the options McDonagh has when he drags Catholicism, suicide, and redemption through the front door of the Connor’s small, grimy house. Having firmly anchored his drama in the minutia, he and director Brendan Hughes, a third-year director at the Drama school, can tread as lightly or as heavily over these larger issues as they deem appropriate, resulting in a tightly-written, well-acted evening at the Yale Repertory Theatre that stings with poignancy, wows in its simplicity, and chases with black humor in perfect balance.

The title makes reference to Sam Shepard’s “True West” — another grim tale of sibling rivalry — and ironically nods to the American West, a grandiose and mythical place where morality is cut-and-dried. McDonagh’s world, however, is insular and has no clear moral order.

By far, the greatest achievement in this play and production is the expert creation of Valene (Jacob Knoll), a timid weed who folds in on himself when he sits, and Coleman (David Bardeen), his unkempt lummox of an older brother, the kind of guy who will kick a priest in the shin and laugh at the priest’s misfortunes. The brothers are a modern take on Vladimir and Estragon from Samuel Beckett’s “Waiting for Godot,” set against kitchen-sink realism and given regular contact with the outside world. The Connors are both a little mad — but at first we shrug it off because they just returned from burying their father. But it becomes clear that, though the setting is a familiarly dreary Ireland, this pair of clowns exists in some alternate universe where, try as they may, they cannot change their lot.

Valene assumes the financial responsibility for the house after his father’s death, and his leverage becomes problematic, leading to boxing matches of words and memories between the brothers. Verbally, they spar like Martha and George in Edward Albee’s “Who’s Afraid of Virginia Woolf?,” using language as a violent force, making a dangerous sport of one-upmanship as they teeter between humanity and animalistic cruelty. Toward the end of the second act, the Connors attempt to put a lifetime of grudges behind them, at the behest of their priest, Father Welsh (James Lloyd Renolds). But even the apologies become acts of aggression. In a mesmerizing scene, the increasingly hostile wits comes to a head when Coleman, like Albee’s George, grabs a rifle and trains it on Valene’s chest. The difference between Albee and McDonagh however, is that McDonagh’s gun is actually loaded.

And that fact makes McDonagh’s world all the more lonely. McDonagh accepts a palpable reality that is refused by Albee and Beckett — and his play is more cruel because of it. The Connors are unable to comprehend death but they wield the power to take it away from anyone at any moment. It’s a wonder that the brothers have managed to coexist for so many years, having no sense of consequences for their actions. At one point, in a fury, Coleman turns the living room into a war zone by deliberately smashing each of Valene’s 46 ceramic religious figurines, which shatter into a thousand pieces when not reduced immediately to dust. Then Coleman gathers himself.

“Maybe we can glue some of them together,” he offers. “Do you still have your superglue?”

“I do have me superglue,” Valene replies, “although I think the top’s gone hard.”

“Aye,” Coleman nods, earnestly, “that’s the trouble with superglue.”

Knoll and Bardeen rightly resist going over the top with physical humor. “The Lonesome West” easily — and tragically — could be a farce. But Hughes’ production is a smart, haunting tale of human instincts and complex relationships. Hughes and his actors thankfully see the humanity of their characters before the humor — the taytos more clearly than the crucifix that’s centered above the mantle. The playfulness of McDonagh’s voice makes “The Lonesome West” seem like absurdist confectionery, but it’s the play’s darker underbelly that will seize you and refuse to let go as you stride down the sidewalk away from the theater.