IT IS HARD to know what to think about Rosie Ruiz. Either she has (almost) pulled one of the great escapades in the history of sports and is quietly chortling about it now, or she is being meanly deprived of savoring a remarkable physical feat.

Miss Ruiz, of course, is the young runner who was officially proclaimed the women's winner in the Boston Marathon last Monday. She had no more than walked away with her laurel wreath, however, when others began to say, first in whispers but soon in full voice, that she had won the race without running it.

The evidence has been piling up ever since. None of the acknowledged leaders in the race recalls seeing Miss Ruiz on the course until she approached the finish line. Some of them say that when they did first see her, she didn't look near enough death to have run 26 miles. The Boston Globe reports that she doesn't appear in a single frame of film taken by 10 photographers it had at the event. And a Harvard senior has come up with a plausible explanaton: he says he saw a woman stuble out of the crowd and join the race just a mile from the finish line.

To be added to that is the suggestion of a New York woman that the same thing happened in the New York Marathon -- Miss Ruiz's only other comptitive race. That woman says she and Miss Ruiz rode the subway together on the day of the race to a station near the finish line.

The evidence is all circumstantial, but pretty convincing, don't you think? If so, read on.

Miss Ruiz insists she ran every step of those 26-plus miles. A police officer says she was the first woman to reach Heartbreak Hill, six miles from the finish. Two New Yorkers say she was the first woman to pass the 25-mile point. And a spectator from Needham, insists Miss Ruiz took a water cup from her hand during the race.

Obviously, no one but Miss Ruiz will ever know whether she ran all that way or not. The officials can't be sure. They take note of only the first 100 runners past each checkpoint, a curious procedure when a woman champion is to be proclaimed and no woman is among the top 100. Obviously, the officials ought to do better, but when a race starts with 5,400 compeitors and offers, as every marathon does, innumerable opportunities for cheating, keeping the final result honest depends heavily on the integrity of those who run.

Miss Ruiz may be like that American runner who crossed the marathon's finish line first in 1904 Olympics at St. Louis to be disqualified becaused it turned out that he had ridden for 10 miles in a car. So you see, there is a precedent fo this sort of thing. Nevertheless, getting there is supposed to be half of the fun. Some streak in people who don't think any of this could be fun, however, is secretly gratified by the idea that Miss Ruiz rode and pulled a fast one on the judges. But this sentiment must at all costs be resisted. Fair is fair, and anyhow think of the example and so forth. Non-runners spoiling for evidence that the Adidas set is not necessarily morally superior to them are going to have to be big about it.