THE CARTER proposals on illegal, or "undocumented," aliens are, as critics charge, "a patchwork compromise that attempts to respond to a range of opposing points of view." Most social policies are - and that's as much a strength as a weakness. In fact, the proposals represent, as the President states, Cabinet-level study (by successive administrations) and the groundwork laid by the key legislators Reps. Rodino and Eilberg and Sens. Eastland and Kennedy. The country has never had an explicit, comprehensive set of policies meant, in Mr. Carter's words, "to help markedly reduce the increasing flow of undocumented aliens in this country and to regulate the presence of the millions of undocumented aliens already here," Now it can choose.

Not everyone wants to reduce the flow: employers seeking cut-rate labor, for instance, and Hispanic Americans welcoming kin. But two groups that do are those troubled by labor competition from alens and those concerned about overhead costs. Mr. Carter would tighten enforcement at the Mexican border and lesser entry points. He would seek source-country cooperation, especially Mexico's, even though few expect Mexico either to close its border (and raise its already disastrous unemployment level) or to conduct the social revolution needed to give its people jobs.

He also proposes to put civil penalties on employers of illegal labor, hoping thereby to tarnish the lure. Such legislation is needed, but it faces formidable opponents: civil libertarians alarmed (unjustifiably, in our view) by the specter of a national ID system; Hispanic Americans fearful (with more reason) of getting caught in the illegal-alien dragnet; employers claiming the new controls would be too heavy; law-enforcement zealots and no-growth proponents claiming the controls would be too light.

Even more controversial are the proposals affecting illegals already resident. We think Mr. Carter had to propose, as he did, that illegal aliens who have been here over seven years be given permanent-alien status, affording eligibility for federal benefits and for eventual citizenship. It is in the nature of amnesty to excuse - if not in fact to reward - law-breaking. But it would be hard to dig out and deport the "over-sevens." If the figure sounds arbitrary, any cutoff would be.

The "under-sevens," almost certainly a much larger group, would be granted a new temporary-alien status and assured of not being deported for five years, during which time they would be counted and registered (but not given federal benefits) and their eventual fate decided; meanwhile new illegals, if caught, would be thrown out. This is a disquieting proposal: It creates a new legal class of second-class citizen. It is an incentive both for new illegal aliens to sneak in and for old under-seven group. The position of the already aggrieved Hispanic-American community could be complicated. We nonetheless lean to supporting the concept. It represents a game effort to catch hold of a problem that otherwise will lurch even further out of control. We have seen no more sensible alternative suggested by the critics.

Illegal aliens are the ultimate international status symbol. If the United States were a police state - if it were not, in fact, a mecca in the eyes of millions - it would not have the problem. This is a nice thought - but the problem remains entirely real. The Carter proposals won't by a long shot sove it. But they will engage the political system with it. Given past neglect, that's major progress.