"KNOCK, KNOCK" (the ancient outrage goes).

"Who's there?"

"Eskimo Christian Italian."

"Eskimo Christian Italian. Who?"

"Eskimo Christian Italian No Lies."

Har, har, har and so forth -- except that now the answer would be different: "Whaddya mean Eskimo Christian Italian Who? I'm your next Supreme Court Appointee."

Well, almost. Forgive us, but these bleak thoughts forced themselves upon our weary consciousness as the political argument (if that's what it was) turned ever so briefly to the propriety of Gov. Reagan's announcing that he would be of a mind to put a Person on the Supreme court if it came to that. The "if-elected-I-would-name-a . . ." syndrome is by now all too familiar, and any attempt to reverse it is probably doomed.

We still insist on registering some faint, residual protest at the idea of stocking the judicial and executive ponds with people whose distinguishing characteristic is first their ethnic or biological makeup as it relates to a political constituency somewhere and, second, their particular talent. But since no one has ever admitted to doing it that way, and since there is merit in making a deliberate effort to overcome discriminatory assumptions and reflexes from the past, it's just very hard to get a productive argument going on all this.

If you have any question about that, just look at the one that developed. From the White House, trapped between mutually contradictory impulses to 1) condemn Mr. Reagan for playing interest-group politics and 2) call attention to its own conferral of honors on the selfsame "interest groups," came some circularly dizzying remarks in the wake of the Reagan announcement. It was pointed out, first, that it was inappropriate for the Republican candidate to have promised a seat on the court for a female, although a distinction was maintained between that and Jimmy Carter's declaration that while it would by wrong to promise such an appointment, he would "be honored" to be the fellow who put the first female on the court. His extraordinary record of appointing women to the lower federal courts was pointed with (justifiable) pride.

There was also some White House displeasure expressed over Mr. Reagan's overtures to an Italian American group, although there was a little contention as to whether he had actually promised the Italian Americans a Supreme Court nominee or just said he would consider such a move. Either way, as with the female justice, he shouldn't have done it, and either way the Carter White House may be the last place on earth that should issue complaints about this ethnic and interest-group politicking with federal judicial appointments. Surely that was Jimmy Carter we remember David Broder writing about in this paper a year ago in Baltimore: "'I will make you an offer,' the President smilingly told Charles Caputo . . . who asked about the chances of expanding the number of Italian Americans on the bench. 'If the Sons of Italy and other distinguished groups aroung the country make recommendations for federal judgeships and if you cannot get an adequqte hearing in Benjamin Civiletti's office, you can come directly to me.'"

We have a feeling of near-certainty that the next Supreme Court justice, whoever she is, will be someone whose qualifications for the job are self-evident. The area of judicial appointments is one in which both candidates have performed a whole lot better than their political and politicized commentary on their performances would let you know. Sorry about that knock-knock joke.