DIONYSUS has long been hailed as the patron saint of the theater, but of late I'm wondering if Merlin isn't the man to take over the title.

Dionysus, of course, was the Greek god of the grape, and it was out of the wine-soaked festivals in his honor that Western theater was born. What Dionysus inspired in his followers was, apparently, trancelike states of ecstasy, and I suppose one of the reasons he seems curiously inappropriate these days to reign over the theater is that the theater is producing very little fare worthy of our deepest ecstasies.

By comparison, Merlin was a mere magician--one who instilled in King Arthur some noble ideals, perhaps, but whose most intriguing quality, as I see it, was that he assumed somewhat capriciously any number of guises and rarely turned up where King Arthur expected him. Now a hawk in the trees, now a fish in the brook, he was a most unpredictable presence. If I've been thinking of him recently, it's because the theater in Washington has also been behaving in a highly capricious fashion.

Anticipation is one of the basic pleasures of my theater-going, as it is for most of us. Give me a press release or show me a flier announcing, for example, that Michael Kidd is going to direct "Room Service" at the Kennedy Center and I automatically begin

Putting a production together in my head. Kidd did the choreography for "Li'l Abner," one of the first Broadway musicals I ever saw as a teen-ager, and to this day I remember my excitement over the spectacular Sadie Hawkins Day romp he concocted for the second act--the women of Dogpatch pursuing the men of Dogpatch with an acrobatic zest that suggested the stage was actually a trampoline.

Factor into that memory the prospect of "Room Service," a farce about a frantic Broadway producer willing to go to any and all ends to get a flea-bitten epic on the boards, and you have something for the imagination to work on. "Room Service" has 22 actors, constantly careering in and out of three slamming doors. Surely, here were the conditions for inspired pandemonium, a succe s de steam in the making.

What happened? "Room Service" was tame stuff at the Kennedy Center, a teapot that never whistled.

Now come at the problem from the other end: the Studio Theatre, which like most of the city's smaller theaters, has had its troubles rallying an acting company of consistent talents. So when the Studio let it be known that it was reviving Lanford Wilson's "Fifth of July," at least part of me--the dubious side--wondered how. A slice of Missouri life, almost Chekhovian in its texture, the play demands, above all, a tightly knit ensemble to depict a houseful of 1960s protesters, more or less marooned in the 1970s. What's more, I had seen "Fifth of July" toward the end of its Broadway run--admittedly, a night two understudies had been rushed into the breech--and I had found the play slightly tedious and just a little mean-spirited.

So I can't say I would have placed a sizable bet beforehand on the Studio's chances. The upshot this time? One of the superior productions of the Washington season, directed and acted with a kind of love I hadn't seen in the theater, certainly not at the Studio, for months. And there--in the role of a coke-sniffing heiress with a freeze-dried brain--was an actress, Rosemary Walsh, who was doing something truly remarkable. Flipped out, prey to every neurosis, real and imagined, that could be inflicted on a pampered dropout, Walsh didn't once downplay the character's colossal absorption in her own extensive problems. But at the same time, she managed to be vitally interested in the problems of everyone else. Quite a trick.

Who, for that matter, would have expected The Source's revival of "Equus"? In its original staging, the London and Broadway hit had played the National with top-of-the-line performers and those awesome actor/horses conceived in the fertile imagination of designer John Napier. Surely all of the play's values had been wrung dry, its depths fully plumbed. And the Source, like so many of our smaller theaters, is perpetually pinched for funds. Well, the Source had put its finger on Robert McNamara, a director uncannily attuned to the play and who, funds or no funds, was determined to re-animate every little corner of a familiar script. To that end, he won two exceptional performances--from Krystov Lindquist, as the tormented stableboy, and from Marcia Gay Harden, as the young girl who seduces him.

This is the sort of thing that drives crystal-ball gazers nuts.

It would be folly to think such surprises turn up weekly. They don't. The act of getting a play successfully on its feet depends on the fine meshing of so many disparate talents and so many imponderable temperaments that failure is the general rule. There's no shame there. You can't do a triple somersault on the flying trapeze every time, and the theater, in its way, is no less risky an endeavor.

I think that may be why the Kennedy Center seems to dwell under such a cloud of public disenchantment these days. It has not proved risk-free. For whatever reasons--of chance or error--the mishaps have been piling up. You had to be grateful merely for getting away from the TV set to take much delight in "Twice Around the Park." Brad Davis and Kathleen Turner playing sado-masochistic games with each other as a mad rapist and his not-so-helpless victim in "Toyer" generated more heat in the billing than they did on the stage. (That's anticipation at work, again.) There was the courtroom drama "Outrage," which lived up to its title only by virtue of its jerry-built structure. Soon after, "Make and Break" pulled into town, trailing its London laurels, and promptly tripped on them. If the sprightly revival of "You Can't Take It with You" hadn't reversed the downward slide, the Kennedy Center, I suspect, would be sitting in the Potomac right now.

And yet, this much can be said in its defense. The Center is a theater (four theaters, really) like any other. Because of its size, its national prestige and the hoopla invariably attending its productions, it is thought to be immune from the general capriciousness of the art form. Not so. The Center is fated to stumble like all the rest. The stumbles just happen to be more visible--and costlier--than most.

Yes, this is a distressing state of affairs. But a certain amount of democratic solace goes with it. Everyone, you see, is up against the same whimsical odds. Big theaters, little theaters, storefront theaters. Somehow, that strikes me as encouraging. It may make theatrical life easier to have a vast support staff, budgets for sets and costumes, and the ability to summon gifted performers at the drop of a play title. But in the final count, it doesn't help that much. Each production is built from the the ground up and establishes--or doesn't establish--its own rules and dynamics along the way. Each production is an experiment without precedent.

True, Arena Stage often seems to manage the propitious laboratory conditions with some regularity. But just pause a minute, while you're mulling over the delights of "Candide," and recall the protracted agonies of "Cymbeline," quite possibly the season's silliest offering. The Folger has shaped up, under the leadership of John Neville-Andrews, as a bright space to watch, but not that long ago it was making terribly hollow noises and futile gestures. If this year the New Playwrights' hit upon "Out of the Reach of Children" and "And They Dance Real Slow in Jackson," back-to-back crowd-pleasers, it was after how many years of scratching the dirt fruitlessly?

I'd like to say I have the key to such mysterious goings-on, but I don't. I have noticed a trend of late, and whether or not it's actually lowering the astronomical odds against success, it is a heartening development. There's an increasing amount of traffic among our theaters. Rivalries continue to exist and when grant proposals go out, it's still every theater for itself. But the walls are coming down here and there and personnel are shuttling back and forth through the gaps.

Marcia Gay Harden, after her stunning supporting performance in "Equus," migrated south a few city blocks for "And They Dance Real Slow in Jackson," where she galvanized the whole play as the wheelchair-ridden victim of a mean-spirited Indiana town. Remember that pint-sized delight Yeardley Smith, who emitted steam from her ears in New Playwrights' "Bride of Sirocco?" The same Yeardley Smith who popped up this season at Arena in "The Imaginary Invalid" and "On the Razzle." Even the actors in the Arena company, generally considered the best berth in town, have sallied beyond the portals--Richard Bauer to the Folger, where he lent grave mischief to Shylock; and Stanley Anderson to the Round House Theatre, where he's helping infuse the current "Talley's Folly" with warmth and humor.

Or take "Burrhead," an intriguing if flawed new drama that recently closed at New Playwrights'. Playing its dusty backwoods heroine was Marcia Gay Harden again. One of its two directors was James Nicola, a producing associate on the literary staff at Arena. And the set was by Russell Metheny, who has been functioning as the acting artistic director at the Studio, which hatched that superlative "Fifth of July."

What happens in such cases of free exchange is that established patterns get broken down, a way of looking at things is subtly altered by the introduction of a new actor, a fresh perspective, an idea from the outside. Routines, which are the bane of any theater as they are of any life, are not so easily fallen into. For years, David Cromwell was automatically cast as the fool whenever the Folger did Shakespeare. Ever since he left for other theaters that see him in other lights, he's been a far more persuasive performer. As Norman, "The Dresser" in Olney Theater's revival of the London hit, he's shed his old skin entirely. Shuffling the troupes may not be the answer, but it can be a productive tactic.

Still, the reality persists. For all the planning, the considered casting, the deep thought and late-night rehearsal, theater is quixotic business. When we talk of a particularly impressive production, it's no accident that "magic" is the word we use. Or that players who are hitting their stride are said to cast a "spell." Which is probably why Merlin, that old enchanter, keeps coming to my mind.

Necromancers play fast and quick with us. In the general uncertainty they engender, this much is certain: If you're looking to the right, the miracle will happen to the left. Plan for it on Tuesday, and it is likely to occur on Wednesday. The same holds for theater. No one has the sure-fire formula. As a result, everyone does.