NOT TOO long ago, in the middle of a play that had nothing at all to do with guitars -- that's precisely what I found myself musing about. Guitars and the people who tended to play them back in the 1960s.

I think I know why.

Guitars, if you will bear with me for a paragraph or two, were the ubiquitous instrument of the 1960s. Wherever you went, someone -- usually in a long flowered dress, sandals, headband, Indian tunic, patched jeans or some combination of the above -- was there before you, guitar resting on the knees, all too ready to take requests. I've hated the guitar ever since.

I've hated it because most of those who felt called upon to play it didn't know how. Every song was shoehorned into one or two keys at best, and set to the same relentlessly plodding rhythm. No one seemed to object that the musician's credentials extended no further than his desire to commune. Everyone beamed and mumbled beatifically, "How many roads must a man walk down . . . "

So, the other night in the theater, when I was thinking about guitars, my subconscious was clearly trying to tell me something. The players certainly weren't. They were pretty inept -- not merely miscast in their roles, but miscast, I suspect, in their profession. The audience went right along, however, and at the end the applause was considerate. The actors, I realized afterwards, were the recipients of the same benevolent indulgence my generation once lavished on the guitarists in their midst.

True, it is very hard to be an actor these days and actors deserve some charity. Meaningful employment is rare and the pay scale is patently ludicrous. But it's also very easy to be an actor: You merely say you are. Unlike most of the performing artists in this city, actors are largely a self-anointed breed. Taking into account some vague yearnings in their souls, factoring in a desire for the fabled glamor of a life in the theater, and maybe remembering Aunt Suzie's warm words of praise, they proclaim their ambitions. The proclamation suffices for certification. At this point, charity becomes harder to muster.

Perhaps they think about training -- maybe a class here or there -- but the basic urge is to find a stage, learn the lines and get up and do it for the customers. No other art form suffers quite such premature displays from its practitioners. The dancer who can't yet manage a split ordinarily doesn't get to do a cancan for the crowd. The pianist knows he's got years of Czerny exercises ahead of him before anyone other than close friends and relatives will lend an ear. The coloratura soprano who can't go beyond high C usually stays out of the public eye until she can, while the harpist whose fingers keep getting tangled in the strings keeps his glissandi to himself.

The actor doesn't stay tucked away, probably because the essential skills of acting are far more difficult to pinpoint. Assuming he can learn lines and doesn't careen into the furniture, he seems ready to take on the task. The inspiration of opening night, the last-minute shot of adrenaline, the sudden injection of magic are expected to take care of the rest. They rarely do.

The movies may be partially to blame. Our national mythology is replete with tales of overnight discoveries -- sweet young things whisked out of drugstores and onto the silver screen; timid understudies who are thrust onstage at the last moment and win a standing ovation. If you land on a magazine cover regularly enough these days, it seems to follow that you eventually land a part on TV. No wonder so many neophyte actors think that acting is a snap -- a matter of having the right hairstyle or a thick enough mustache.

What acting really is, of course, is a kind of friendly persuasion. Using the particulars of his own person -- his voice, his body, his aura -- the actor persuades us that he, in fact, is someone else. But it's quite the opposite of a masquerade. Stripping away the defenses the rest of us rely on to protect ourselves in daily life, he makes himself psychologically naked and utterly vulnerable, and builds from there. Disguise has nothing to do with it; exposure is all. There are tricks and techniques of communicating, perhaps, but at the core of every good performance is a kind of ruthless self-honesty that most of us avoid.

Since you can't really measure the qualities we're talking about -- not the way you can, if need be, measure a singer's lung power or the height of a dancer's leap -- a lot of actors show themselves before they're ready. They have convinced themselves that they have the stuff. Who's to say otherwise?

This is not to imply there is no good acting in Washington. The Kennedy Center will engage now and again the services of an Irene Worth or a Zoe Caldwell, consummate actresses both. The cast of "The Dining Room" constituted a marvelous ensemble. And last year at about this time, Christopher Plummer, as a splendidly evil Iago, was burning scorch marks into the stage of the Warner Theatre. But those actors were just passing through.

For the home-grown talent, you have to look to Arena's resident company where a Stanley Anderson, a Richard Bauer, a Halo Wines and (although he's since moved on) a Robert Westenberg have amassed an extraordinary portfolio of performances. The common complaint about resident companies -- you always see the same faces -- is precisely what makes them such good yardsticks for taking stock of talent. An actor can beguile us only once or twice with mannerisms and idiosyncracies. If he's to appear in four or five plays a season, he has to do more or run the real risk of getting found out.

In that sense, the Folger Theatre Group's recent move to establish a resident company this season has to be considered a major step forward. And while the Round House Theatre's youthful company is still green and tentative, it, too, looms as a potential seedbed. (You'll note, by the way, that two of the Folger's new resident performers are Round House alumni.)

For the most part, however, the reality of acting in this city is that it is mediocre and sadly self-serving. It also knows no modesty. The Studio Theatre blithely takes on Shakespeare -- or the Source, Brecht -- with little apparent awareness of the immensity of the challenge. The Rep has a tendency to confuse street behavior with performing skills. And though the New Playwrights' Theatre claims its first order of business is discovering new plays, it is sometimes difficult to appreciate the scripts at their true value because the actors are horning in with errors of their own. For every authentic actor who turns up on a local stage, there are 20 dilettantes, and the real actor usually ends up running off to New York anyway.

This is, of course, seditious thinking. Ever since the arts began booming in the 1970s, we have been lectured time and again that our artists must be nurtured. Not to pay them heed is to slam the door on the future. If we care, we should encourage and coddle and applaud. Criticism, if there must be criticism, should be gentle and constructive. We may, however, have gone overboard. Who's serving whom?

Like most theatergoers, when I watch a play, it's the play I want to think about. Certainly not guitars. However, my mind strays occasionally and I've learned not to feel guilty about it. After all, it's the actors' function to shape and channel our thoughts.

If we're running over the laundry list when the performer is rallying friends, Romans and countrymen, if the leading lady can't quite banish our preoccupation with an unpaid electric bill, if the Shakespearean rustics are prompting reveries of Acapulco in the winter, the fault is not ours.

It merely means that the actor, like the ubiquitous guitarist of the 1960s, hasn't mastered the instrument.