Self-knowledge isn’t what it’s cracked up to be.

Or at least it never used to be.

Among the many, many things that have changed in the 2,500 years since the debut of Sophocles’ “Oedipus” is the whole concept of what it means to know oneself — or, rather, what one could hope to gain from such information.

Steven Berkoff’s gorgeous but psychologically muted production, which opened Tuesday night at Spoleto Festival USA, tries to split the difference between these extremes.

By pairing his own demotic text with sumptuous tableaus straight off an Old Masters painter’s easel, Berkoff offers eye- and ear-catching glimpses into our inward-gazing present and our skyward-gazing past.

“In truth, we grow,” says the blind seer Tiresias, one of the men who leads Oedipus toward solving the murder mystery he insists on tackling. But by the preordained standards of the ancient Greeks, we only grow into the shape that the gods had measured out for us.

When it comes to the gods, Berkoff’s go-to visual reference, aided by Michael Vale’s superb lighting design, is clearly the Christian one.

His eight-man chorus is arrayed on either side of Oedipus (Daniel Rabin) in a formation eerily reminiscent of “The Last Supper,” and Tiresias enters raised up in the air with his arms out in crucifixion position.

While Berkoff’s staging nods to the sublime, his adaptation is agreeably earthy, complete with the occasional bit of salty language (though not the 12-letter word that is perhaps most applicable here).

And as Sophocles’ whodunit gradually, satisfyingly turns into a youdunit — the fate of Thebes hinges on Oedipus discovering who murdered the former king, paving the way for his marriage to Queen Jocasta (Anita Dobson) — Berkoff elevates his syntax to match the heightened stakes.

Notwithstanding the heights of his text and the beautifully calibrated precision of his chorus though, some of Berkoff’s decisions fall flat.

The somewhat arbitrary adoption of masks more than an hour into the piece muffles the impact of a final, harrowing mask used after the climactic moments of violence.

More damaging is the bombastic performance style favored by much of the cast; this is presumably a choice made by Berkoff, himself no shrinking violet in past productions.

The prime example of this is Rabin, whose matinee-idol charisma is belied by his nuance-free delivery. Rabin plants his feet, bends his knees and splays out his hands to convey rage, relief, grandeur, indignation and a few other emotions.

Berkoff’s text sounds splendid out of his mouth, but the performance is no more layered than those of his chorus members, who periodically break out to play the king’s various truth-tellers.

The one exception to this, curiously, is Berkoff himself, who plays Oedipus’ uncle Creon. In the middle of the most stentorian announcements, he twinkles with the Machiavellian delight of someone who’s been around long enough to realize that Oedipus’s downfall was a question of when, not if.

He’s the only one who seems to see the central tragedy as not only an inevitability but also a potential opportunity. That’s the kind of knowledge that trumps self-knowledge regardless of the century.

Eric Grode is a theater critic who teaches arts journalism at Syracuse University.