And now, before we all sit down in front of the fireplace to read the 60 briefs filed in the Allan Bakke case, a short pause . . .

For the past several months, a lot of legal attention has been focused on discovering the exact moment when - shazam! - a goal is turned into a quota and affirmative action becomes reverse discrimination. But very little mention has been made of the silent partner in this case, that great American ideal, The Merit System.

Mr. Bakke, a 37-year-old engineer, contend that the only reason he isn't Dr. Bakke today is because he's white, and the University of California gave "his seat" to a less qualified minority member. Now, it's always seemed to me that Bakke had a better case for age discrimination than race. At 32, he was rejected by 13 medical schools, not just one.

But beyond issues of race or age, Bakke's argument implies that there is some objective, fair and immutable way in which a medical school measures "merit." In fact, however, merit systems rest on shifting standards. The criteria by which we say that John Jones "merits" admission and Sam Smith does not are as imperfect and chaning as the humans who set them up.

There are a lot of obviously flexible criteria for admission - geographic distribution, "pull," extra-curricular activities, life experience and more. But the merit system for medical schools depends largely on college grades and admission-test scores. These numbers can, theoretically, be worked out in some cool mathematical equation.

But even this "numbers game" can actually be far less "fair" than it appears.

Grades are inflated here and deflated there. One university's A is the intellectual equivalent of another university's C-plus. The medical-school admissions committee needs a calibrator to correct for all the variables of academic grading.

The tests are another story. The Medical School Admissions Test (MSAT) has been the one uniform standard of comparison for all applicants. Yet these tests have changed so radically that the students who "clearly, objectively and fairly" deserved a place in the class of 1976 might well have been rejected in 1977.

Last April, 30,000 pre-med applicants took an exam that has been called "The Thinking Person's Filter." While the old MSATs tested the student's warehouse of rote knowledge, this new exam was created to determine which students were able to solve complex problems. It was a test far fariendlier to the nonscience majors than the old one, and now medical schools may accept more "rounded" college graduates than before.

The standards have changed - the social standards, not the academic ones - and so the merit system has changed.

The medical community is now trying to devise a personality test that would separate out the premed students who will be able to take care of people, not just test tubes.

Does all that mean that the earlier crop of students should never have been accepted to medical school? No, not necessarily. It means that merit is a matter of definition. Merit to a large degree is what those who define it say it is.

Therefore, it is always possible to set up a perfectly "objective" set of criteria for admissions to medical school - or any other school - that could still effectively eliminate almost all the people you want to eliminate.

You could even set up a "merit system" that favored minorities and the poor, by insisting, for example, that only those - of any race, you understand - who have spent a significant part of their lives in the inner-city ghettos deserved a seat.

Merit is an objective measurement of a subjective set of criteria. It is defined by the changing attitudes of the people in charge.

If Bakke's position is affirmed by the Supreme Court, medical schools may return to a policy that virtually excludes minorities, but they won't be restoring a fair, impartial or equal merit system. There is no such a thing.