It is being said that it was an arms control summit, meaning in the main that no agreement was reported on the regional conflicts that express the deepest differences between the two superpowers. But that's too glib. Something happened at the summit, or, perhaps better, something is happening to make conceivable the resolution or easing of some of these disputes on terms serving the American interest.

It is not an accident and it is not a sham, I think, that in the Persian Gulf, Afghanistan and Nicaragua, to name three places, there are hints of brightening. A false dawn? Perhaps. But in the American effort that Jimmy Carter began and Ronald Reagan confirmed, and in the Soviet mood of review associated with Mikhail Gorbachev, new possibilities faintly stir.

The important thing about the three conflicts cited is that they are ''mature.'' They have all been going on nearly a decade. It is as clear as it gets in these situations what the odds and the costs are. Channels of mediation are available. These are not raw new disputes where the powers or their proxies are testing their strength and where the international community has not even a feeble grip on the situation. Something could perhaps be done about these disputes.

In the Gulf, the latest word is that the Soviets are finally responding to pressure to support a second United Nations resolution punishing Iran for rejecting the cease-fire called for in the first. Two conditions are reported. One is that the United States must pass a law to prevent further secret arms shipments. The Soviet purpose is understandable here, although the request for a law is mischievous. The second is that policing of sanctions should be done by a U.N. fleet. This would reduce the political advantage the United States gets by sailing its own ships in the Gulf, and it would legitimize a new Soviet Gulf role. But -- on the plus side -- it would also reduce American exposure and firm up the constraints on Iran.

Gorbachev has been talking about applying his ''new thinking'' to international affairs, and this Soviet feeler is apparently an example of it. Incontestably, it requires some rigorous new thinking from the United States. Does anyone argue that our Gulf policy is already so successful and promising that we have no need for it?

In Afghanistan, we are into a rather confusing public discussion of whether Reagan promised, and if so whether he was right to promise, cutting off aid to the Afghan resistance either when a prospective Soviet troop withdrawal begins or at some later phase of withdrawal. But surely the significant aspect of this discussion lies in the fact that the Afghan resistance has pushed the question of Soviet withdrawal to nitty-gritty end-game points like this one.

We Americans cannot avoid asking ourselves whether Gorbachev is trying to trick us -- to gain on the south lawn of the White House what his troops could not win on the Afghan battlefield. But almost certainly the Soviets are conducting a more anguished and momentous debate on whether they can count on Reagan to deliver on his pledge to be ''helpful,'' not simply to bleed Moscow, if Moscow will only set a prompt-withdrawal clock ticking. Cheaply, we are holding up one end of a war for which Moscow is paying dearly. Almost every country in the world and the whole American political spectrum believe we are right to do what we are doing and they are wrong to do what they are doing. Afghans are reclaiming Afghanistan.

In Nicaragua, we are into more postsummit churning masking a potential end-game. The Sandinistas say they plan or propose, whichever, to build what would be a giant, region-menacing defense force with Soviet aid. But Gorbachev broaches the completely contrary subject of a military-aid cutoff perhaps linked to the Central America peace plan.

Again, we have to ensure Gorbachev is not playing games. But we also have to keep our balance and to ask how the version of a close militarized Soviet-Nicaraguan future depicted in Managua can fit with the strategy of a Kremlin leader ostensibly attempting to reduce the Soviet international burden and to stabilize relations with the United States. Perhaps Gorbachev is practicing a monstrous deceit. If he is, we will have to deal with it -- and not only in Nicaragua. Meanwhile, we have to see if that is his true path.