A Martian looking at the way Congress treats the administration's aid requests for Israel and El Salvador might conclude that our political system makes potentially life- or-death decisions about dependent countries in truly inscrutable ways.

Israel, already far and away the dominant military power in its region, is being given-- no questions asked--a third of a billion dollars more than the several billion dollars that the administration asked for it. Meanwhile, El Salvador, fighting against the very real possibility of a guerrilla takeover, is being required to jump a series of extremely high political hurdles in order to receive a level of funding (6 or 7 percent of Israel's) that is barely adequate to keep its nose above water.

Congressional sponsors of this split-level approach, like Rep. Stephen Solarz (D- N.Y.), are ready to explain it:

Israel is a democracy and a strategic ally, and it will sooner take further risks for peace if it is shown proper appreciation for the risks it just assumed in its new agreement with Lebanon. Salvador is something less than a democracy and a strategic ally, and its government probably cannot avoid a guerrilla takeover unless it is pressed in a friendly but firm way to tame its undisciplined armed forces and negotiate with its foes.

These are not neglible considerations-- Israel and El Salvador do have different weights and predicaments--but they leave me feeling queasy.

There is, first, the matter of the Israelis' using their political influence in the American Jewish community in order to play a more pliant Congress against the president and obtain that extra aid. True, in this aid bill as in the last, the Reagan administration has seemed oddly indifferent to such congressional inroads into its foreign policy prerogatives. Still, it seems to me a wrongheaded and offensive form of intervention in the American political system, and one that is storing up some mighty resentments. Certainly it frees up an American president to play to the Israeli opposition and public in whatever effective ways he can.

The notion that aid not only rewards Israel for the last step toward peace but relaxes it for the next one is too simple. The Israelis, by going all the way to Beirut, landed themselves in a quagmire. U.S. diplomacy is pulling them at least part way out. They have little claim to be paid for a service we are doing them. Nor can one look at Israel's position in the West Bank and ignore that aid can be a relaxant but it can also reinforce a disposition to resist American policy pleadings.

The congressional treatment of El Salvador is questionable on its own terms. El Salvador has no popular constitutency in the United States and does not enjoy Israel's longtime consensus of favor on strategic and moral grounds. Thus lightly moored, it is vulnerable to buffeting by the political winds of the day and has become the object of the most intense liberal-vs.-conservative foreign policy struggle that Americans have known since Vietnam. The strength of the liberal view is marked by the conditions-- talks, reforms, rights--put on the new aid.

I have felt the tug, the itch, to lay on conditions, and the reasons go beyond feeling good. Conditions can help put the "good" Salvadorans in a position to say to their partners in power, "The Americans insist on change." There is something to this line. Without the pressure, El Salvador might already have collapsed.

But there is not everything to this line, just as there is not everything to the opposite line of permissiveness as preached in respect to Israel. Some Americans believe rights are the proper condition; some believe it is reforms, some believe it is talks. We compromise among ourselves by demanding that Salvador do them all. But we may already be perilously close to an overload. The structures are not there to carry the full burden.

At this point the congressional liberals, having met Ronald Reagan on his own terms and agreed that the outcome counts, shrug and say that there are certain circumstances of Salvadoran inadequacy in which they would bail out, or at least cut back--which might have the same effect. To promise to go all the way regardless of how the Salvadorans perform, they say, puts Salvadoran hands on the American steering wheel and probably ensures a fiasco in the bargain.

It would be enough for me if the people who are generous with Israel would have a little dialogue, strictly for educational purposes, with the people who are tight with El Salvador. Some of them could do it while looking in the shaving mirror.