Predictably, the recent visit of Pakistani President Zia sparked a brisk debate over the wisdom of the Reagan embrace of Pakistan, and settled nothing. Such is the sensitivity of the real issue that the argument was never truly joined.

Zia promised not to build a nuclear bomb. Congressional critics told us not to believe him. But administration officials said we should take his word for it. For them to have done otherwise would have risked rejection of their $3.2 billion, six-year military and economic aid program for Pakistan under rules of the Nuclear Non-Proliferation Act.

Zia was rightly taken to task by the press and Congress for his dictatorial rule, his political repression, his low grades from Amnesty International. His reply -- that nobody's perfect and, anyway, democracy takes time in developing Third World nations--wasn't nearly good enough for human-rights activists. 5 But the administration smiled politely. Zia stands as Exhibit A in the Reagan case, as laid out by U.N. ambassador Jeane Kirkpatrick, for doing business with strategically placed authoritarian (as distinct from totalitarian, which is to say communist) regimes. So Ronald Reagan gave Zia a huge hello and placed him "at the front rank of the nations shouldering a great responsibility for mankind."

For as long as the issue is dealt with in this fashion, the tax-paying public is going to be in a poor way to judge whether Zia is (a) a faithless, ruthless opportunist, to be cold-shouldered, or (b) a potential asset to be generously, if gingerly, encouraged.

Prudence counsels the latter course -- if you are prepared to be a little cynical. Indeed, by its juxtaposition to Afghanistan, Pakistan offers a perfect test of the choice between the relative wickedness of totalitarian and authoritarian regimes. Pakistan may not be a pretty case, in Amnesty's eyes, but Soviet-occupied Afghanistan today is a human-rights monstrosity. And it is the role that Pakistan might (or might not) play in some resolution of the Soviet's brutal presence in Afghanistan that makes the Pakistan issue so difficult to argue publicly.

Zia won't say it and the Pakistanis hate to have it said. But an open Pakistani border with Afghanistan -- which is to say, the availability of Pakistani territory as a sanctuary and a supply route for the rebels (and a safe haven for some 2.8 million refugees) -- is quite simply a necessity. Without it, the insurgency within Afghanistan would dry up within a matter of weeks.

The result for the Soviets would be the winding down of an ugly, draining war; a free hand to consolidate their grip on Afghanistan in less overtly ruthless ways; an easing of the worldwide condemnation the invasion has earned. This would heighten the threat to U.S. interests in the region, most notably in the Persian Gulf. On its face, it would seem to menace Pakistan itself.

So what would encourage Zia to tighten border controls and make things simpler for the Soviets? Nothing, he has indicated, and U.S. officials tend to believe him. But a large part of the case for generous military and economic aid rests on the estimate of top Reagan policy- makers that Zia is not entirely his own master -- that he must deal with elements profoundly suspicious of the United States, but also fearful of the Soviet Union, and inclined toward accommodation with the superpower next door.

Hence the anguish at high levels over the possibility that the first installment of the new aid program for Pakistan may get lost in the last-minute rush of the lame-duck Congress. If that happens, high administration authorities by no means exclude the possibility that the "accommodationists" in the Zia government might prevail with the argument that, if Pakistan can't count on the Americans, that's all the more reason for cutting a deal with the Soviets to close the border and ease the way for a "pacified" Afghanistan. The Soviets would be grateful. The potentially explosive Afghan refugee problem would be solved. Pakistan would somehow be a safer place.

But from an American point of view, it is hard to see how this would advance the interests of either the human-rights critics or those who would seek to deter Pakistan's development as a nuclear power. Withholding American aid would remove any U.S. leverage on the Pakistani government. The question is whether, in a situation where a certain balancing of evils is required, some leverage is not better than none.