AN EVENING PERFORMANCE; New and Selected Short Stories. By George Garrett. Doubleday. 518 pp. $18.95.

THE SHORT STORY is popularly supposed to be having a renaissance. Those who never envisaged or foretold its death, and who are familiar with the brevity of popular rebirths, are little impressed by this announced resurgence. Good short fiction has continued to appear in the better literary magazines and university quarterlies which have always been, as George Garrett points out in his preface, a haven for good stories. They have been stories of great variety, strongly experimental, socially oriented, or dealing head-on with basic human emotions, behavior and needs.

The stories of George Garrett belong to the last of these groups, but he brings to them the formidable resources of his work in poetry and of the off-beat historical fiction of Death of the Fox and The Succession. The dangers for a short-story writer inherent in being also a poet and novelist are very real, and one of the major victories of this splendid collection is that those dangers have been avoided; there is no "poetic prose" -- although there is plenty of poetry in the stories -- as there are none of the lulls and detours which the novel can afford.

Of his stories, Garrett says, "I stand by them one and all with a full awareness that many of them are less than they might be, and none, not one, is as good as it ought to be. . . . Meantime, this is what I have and who I am."

What he has and who he is is a gift for all of us. These are stories never taped down and finished off with a stitch. They are open- ended: these people lived before the story began, and most of them will continue their complex and often desperate lives after its final word. One of Garrett's special triumphs is that, while he opts for the traditional action of moving human beings from here to there, showing their changes in the process, he also forces the reader to imagine something beyond the printed conclusion. Certainly that is a characteristic of the finest kind of short story.

Army life looms large in the book and is responsible for a number of Garrett's funniest (he is very, very funny when he chooses), most vivid and most appalling stories. One of the themes of the book -- perhaps its central theme -- is the grimness of self-discovery, its unforeseeable, irrevocable quality. Just as pride, loyalty, courage, and that battered word, compassion, are seen as the touchstones of what is most valuable and essential in human nature, so cruelty, treachery and brutality are seen as the interior enemy -- the unrecognized but ever-present possibility that any human may inflict or suffer shame. Here cruelty in a variety of forms is seen to be contagious as any plague; applied to the helpless, it can kindle its replica in the most unlikely spot.

In these stories, there is always a double level: the one on which we like to, and tend to believe we do, live, and the one below it, secret until brought suddenly into consciousness. "I was sick of walking about the fine avenues and boulevards of this world where you walk with your head up, strut if you want to like a god, and meanwhile all the time there's an invisible world breeding and thriving. In back rooms, in hidden corners, behind blank smiles." This, from a series of four short pieces grouped under the title "What's the Purpose of the Bayonet?"

Garrett is fascinated by the fringe figures who have in their oddity or loneliness something of the mythical: the circus-woman, grifter, lion-tamer, clown, prisoner, hobo, or, as we unctuously express it, "the physically disadvantaged."

A WORD WHICH frightens Garrett is "purity"; not purity in the sexual sense, but in that of an unflawed field of snow, a desert of printless sand, with no record of the blundering human foot. Humanly speaking, such purity is either an illusion, dangerously held, or a mask worn so long and tightly that the features beneath it have changed secretly beyond recognition. Though the writing is perfectly straightforward, every story carries with it what Garrett refers to as "the old sad weight of complexity." A nurse who witnesses the onslaught of a violent crime and refuses to become involved, loses her capacity for sympathy, first with herself and then with her patients. Full of contempt for them, she addresses herself furiously to becoming a popular and valued nurse. "She felt a sense of exhilaration . . . she saw herself wielding a knife she had not owned before."

It would be all wrong to give the impression that the overall impact of the book is grimness. On the contrary, humor is not only everywhere present, but a number of the stories, including some of the most sobering, are hilarious. A number are concerned also with the nature of justice and its virtual impossibility as humanly applied. In the section headed "In The Briar Patch," the epigram from Isaiah reads in part: "We look for judgment but there is none. . . . But if the achievement of justice is dubious, the search remains vital. It is when the spirit of resistance to cruelty, to smugness, to injustice dies that all is over; resistance is all."

"That's how real resistance goes on," Garrett writes, "and its strength is directly proportionate to the number of people who can let themselves be taken to pieces, piece by piece, without quitting too quickly. It is an ugly business and there are few if any wreaths for them."

Wisely, the book closes with a long story, "Noise of Strangers," which it is no exaggeration to refer to as a contemporary classic. To describe it would be to injure it, but it deals, brilliantly, with the possibility of justice, and its chances. The story moves easily, rich in detail, superb in characterization, to a conclusion that the reader is not likely to forget. In it Garrett's strengths are at their height: atmosphere, characterization, dialogue, scope. Read three or four times, it increases its force. It is very sad, and very funny, and has the kind of gritty pathos which makes it a small masterpiece. Alone, it would be, as we say, worth the price of admission.