Fortune cookies are survivors. Through Szechuan peppercorn invasions, Hunan sauce incursions and threats of Yunnan and Fukien cooking superseding all, fortune cookies remain impervious to Chinese-food fads as they have remained impervious to generations of teeth. The same restaurants that long ago removed chicken chow mein from their menus still serve paper strips that promise "Opportunity knocks only once."

Though fortune cookies no longer yield, as they once did, army recruitment advertisements, and no politician since Nelson Rockfeller has been reported to have stuffed fortune cookies with campaign literature, there are hardly any noticeable changes in the messages; the fortunes are likely to be as stale as their cookie wrappers. Still, the imperatives of science lead us to examine the world in all its facets, to see if the key to evaluating the Chinese restaurants of Washington might not lie in its fortune cookies.

We gathered the cookies from 18 Chinese restaurants, half a dozen from each. Now, it may sound like an easy life, contemplating one's fortune in a hundred variations. But just breaking open all those rigid little confections is a new level of tedium. And then to try to figure out what to do with a couple of quarts of fortune-cookie shards . . .

One learns a lot. One learns by deduction that there are five local schools of fortune cookies, and that three of them use the same cookies, but just fill them with different fortunes. Nobody shuffles the deck very carefully; duplicated fortunes turned up in several batches. One of the hundred-odd cookies had no fortune, but as fortune number 33 reassured me three times in this study, "It is always darkest before the dawn." Another cookie had two fortunes. A third had a blank paper, but I refuse to dwell on the implications of that.

If you pick your Chinese restaurant by its fortune cookies, I predict you will be eating at Imperial Garden. First, the cookies themselves are a nice, smooth pencil-eraser color, with an understated, hardly sweet flavor. Second, I suspect that the waiters write the fortunes to order. One cookie suggested, "You love food; but love sex more." Another ventured, "You are a strong lover." I half-expected a plate of empty cookies for diners to reply to the waiters.

There is convincing evidence for a positive correlation between the quality of the cookie and savoriness of the fortune. The Lotus and the Shanghai clearly have the same source for their snappy little vanilla-flavored cookies, so thin and fragrant that I left myself a secret cache for nibbling later. I kept the fortunes, too, for later nibbling. They promised me a pleasant fellow traveler on a journey and foreign travel with my spouse (perceptive little pastries). They predicted unexpected treasure and presents, new and successful business ventures, a vacation by the sea - then dashed it all with, "You may lose your lover through false reports." Say it isn't so, Lotus, or I'll take my business upstairs to Germaine's.

Everything else was downhill, too, after the Lotus and Shanghai's happy futures. The next 15 restaurants yielded identical cookies - rock-hard, tan and tasteless, with no character beyond their muted rice-flour crunch. Worse, they were a morass of muddy fortunes that lent themselves to no scientiic generalizations. Odd numbers were no more stimulating than evens, high numbers only slightly less stultifying than low. Chinatown and suburbs, yellow and lavender, long fortunes and short: All needed a courageous editor, one who spoke fluent English.

Hu Yuan, for a start, fed me the kind of armchair philosophy that sounds viable until you read it twice and notice that it's meaningless: He ask advice in vain who will not follow it. Failure teaches success. He who suffers remembers. He who reads fortune cookies at Hu Yuan suffers.

Inn of the Eight Immortals left me with a new kind of Chinese Restaurant Syndrome - free-floating guilt. It lectured me in each cookie: It never hurts to crack a smile. You should be content to know you are loved. And twice it reminded me (did I seem a particularly stubborn case?) that kindness is worth more than beauty. I knew the message was squarely aimed at me when it later showed up again at the Szechuan Peking.

Whatever the meal at the Golden Palace, you are likely to leave satisfied after a batch of cookies that encourage you with, "There is much in life - so live." How could one better end dinner than with the restaurant's self-serving little message, "Eat and be happy"? Compare that, for instance, with the batch of cookies at Szechuan Mandarin, no less than two of which warned, "Live it up before it is too late." Should I not have ordered the spareribs?

Ya Shue Yuan gave me the same warning, which set me wondering whether I ought not to be eating in Chinese restaurants altogether. To its credit, Ya Shue Yuan, recognizing the coincidence between dining out and the good life, tells its diners, "There is no cosmetic for beauty like happiness." It even has special fortunes that are obviously aimed at waiters who snitch samples: "Anger makes dull men witty, but it keeps them poor." Take that, short-tempered servers.

Szechuan Peking, on the other hand, has never learned which side its bread is buttered on, reproving and sending its diners packing with "A man cannot spend all his life in frolic."

In the interest of ethnic charm, I think, the fortune-cookie makers hire special copy editors to turn fortunes into pidgen English. They got a little carried away, though, with the Szechuan Garden's "Man who make love to a girl on a hill is not level." Search in vain through your Little Red Book for that one. China Doll creates a new anatomy with "The way to a man's heart is to his stomach."

Then there are the just plain inscrutables. It's easier to untangle a plate of lo mein than the Far East's "The hook bait catches no fish." And did the Dragon Seed mean to tell me I was occupying a table too long by sending "Real friend hard to find, harder to lose"? I am still trying to work out the Seven Seas' "Rest is like fuel - it tires your ambitions."

Fortunately, the fortune-cookie tradition keeps up its standards at old standby restaurants like the Jade Palace - where no less that three cookies promised changes leading to happiness - and Tai Tung, which, knowing of my eating habits, cautions, "Great restraint is called for." They are good, old-fashioned personal messages, not those vague, universal "A friend to all is a foe to none." As one longtime observer of the fortune-cookie scene put it, "You really expect your fortune cookie to pay attention to you. If you can't hold the attention of your fortune cookie, you're really in trouble."

Yet, Fortune cookies have many important roles to play. At Ruby, a grave historical error was righted: Now we know where Franklin Delano Roosevelt must have come up with "The only thing we have to fear is fear itself." Think how different the world might be now if he had, instead, adopted "A wise cracker is a smart cookie." And thank goodness he didn't hang out at Ching Yung, where he might have been haunted by "He who hesitates is lost." Or maybe he did.

So, while people worry about what mysteries lurk in the Moo Shi Pork, they are being diverted from the real meat and potatoes of a Chinese restaurant. The lives of men hang suspended in those dark crevices. Not to be ignored are the messages of the fortune cookie. It was at the Szechuan Peking that the lesson was brought home with "While you read fortune other man take cookie. Solly!" CAPTION: Illustration, no caption; Picture 1, no caption; Picture 2, no caption, By Ellsworth Davis.