The crucial question in the Middle East now is whether the Arabs will have the vision and good sense to join the peace process. In this context, the meeting between PLO leader Yasser Arafat and King Hussein of Jordan can be counted a step in the right direction. Such talks between former enemies would not have taken place a few months ago. Yet the discussions were obviously serious, and Mr. Arafat emerged from them saying that he saw ''some positive elements'' in President Reagan's Middle East peace plan.
To be sure, Mr. Arafat is a long way from accepting the plan, which calls for association of the West Bank with Jordan. The official PLO position is that an independent Palestinian state must be set up in the Israeli-occupied territory. But Mr. Arafat at least is willing to talk about the idea of confederation (once an independent state has been established) and does appear to have given enough of a green light to enable the Jordanian monarch to engage in exploratory talks with Washington without fear of being criticized. So a little progress has been made.
To get King Hussein to actually join the autonomy negotiations, however, is the objective, and his reluctance to get involved remains deep. It is not clear whether his favorable reaction to the Reagan proposals stems from a genuine enthusiasm for them, or is merely a prudent stance given his desire to acquire more US arms. The fact is, he has long believed that the autonomy negotiations are a snare, that they simply delay dealing with the final status of the West Bank while Israel is given breathing time to carry out de facto annexation of the territory. This is why he has said he will never negotiate as long as Prime Minister Begin is in office.
Nonetheless, whatever their misgivings, King Hussein and Mr. Arafat should realize that time is not on their side. The moment is propitious to seize the diplomatic opportunity opened up by the Israeli invasion of Lebanon and not let it slip by as the Arabs have so often done in the past. The mood in the United States is favorable, the mood of the Israeli people is favorable, and the Reagan administration has finally committed itself to a specific initiative. All this could go down the drain unless the Arabs are willing to talk. Mr. Arafat may be in trouble in the PLO as dissident factions, following his meeting with King Hussein, denounce the idea of a Palestinian federation with Jordan. But Mr. Arafat may be out of the picture altogether if American public opinion concludes he is not seriously interested in negotiation.
The Arabs certainly see that a slowdown of the peace initiative would suit Mr. Begin's interests just fine. At the moment the focus of attention is on the US diplomatic effort to get all foreign troops out of Lebanon. With Israel no longer insisting that the remaining PLO fighters pull out before the Syrians and Israelis do, the withdrawal problem now looks to be manageable. Yet this could be deceptive. Israel's insistence on a 25- to 35-mile security zone in southern Lebanon and a key role for its client, Major Haddad - plus the complexities of getting the Syrians and PLO to leave - could drag out the negotiations for some time. Meanwhile, the Israeli grip on the West Bank tightens - to the point where there ostensibly would be little territory left to negotiate about.
It is important, therefore, not to get bogged down in Lebanon at the expense of momentum on the West Bank. This will require, first, the continued vigorous involvement of the United States in the diplomatic process and, second, Arab willingness to shed the passivity and hesitancy of the past.