A few weeks before Secretary Haig's resignation a State Department spokesman was in our office talking about a new unity in US foreign policy. If his hopes were premature then, they could be fulfilled now that President Reagan has appointed a secretary, George Shultz, who describes himself as ''simpatico'' with the administration.
Much speculation has already arisen over what the post-Haig foreign policy might be. The question is, what should it be? Consider some major needs:
* A strong and stable Western alliance.
Policy should be built on the overarching importance of the alliance - militarily, economically, and politically. Mr. Haig's recognition of this, fostered by his NATO experience, has been perhaps the principal contribution of his tenure.
The administration should not lightly sacrifice European interests to its entirely understandable concern for refusing aid and comfort to Moscow. It seemed to be doing so when Mr. Reagan overrode Secretary Haig's objections and imposed new restrictions on technology to block the pipeline from Siberia for natural gas wanted by the Europeans.
The sanctions themselves - like the forthcoming decision on whether to renew the US grain sales agreement with the Soviets - can still be argued. Are they effective? Even if not effective are they morally demanded so long as Moscow flagrantly defies human and national rights in Afghanistan and elsewhere?
But, whatever the US position on sanctions that affect Western Europe and Japan, it should be implemented only with the full knowledge and understanding of the allies. There must be no repetition of the damaging diplomatic slippage that evidently upset Mr. Haig as much as the allies; namely, President Reagan's letting them believe one thing on sanctions when he was in Europe and doing another after he got home.
* Arms reductions.
President Reagan's chief START negotiator, Edward Rowny, says Haig's departure should make no difference to the Geneva talks beginning today. It is to be hoped that this is true in the sense that Secretary Haig, with his strong anti-Soviet credentials, has supported realistic bargaining.
Mr. Haig sees that both sides will have to benefit if agreement is to be reached for the good of mankind. His exit could tempt administration superhawks to try to throw monkey wrenches into the process. Or there simply may be less impetus to move forward without Haig's firm backing of the European interest in checking the nuclear arms race. President Reagan and his new appointee ought to ensure that neither of these outcomes occurs.
* Peace in the Middle East.
In the immediate situation US policy could benefit from a tougher public posture on Israel's Lebanon invasion than Mr. Haig evidently favors. If it is true that President Reagan has been ''tremendously upset'' about the massive civilian tragedy in Lebanon, it would be consistent to let both Israel and international opinion know. The question of the use of American arms for offensive purposes is one for urgent administration attention in line with requirements that Congress be informed.
Mr. Haig reportedly preferred to let Israel achieve its full objectives in Lebanon without White House outcry. The hope would presumably be stability in Lebanon after a political sorting-out in the wake of Israeli elimination of other outside forces and eventual removel of its own. The result up to the time of Mr. Haig's resignation was the apparent failure of Washington to use its influence to reduce the devastating expansion of the Israeli invasion from its originally stated aims.
Now the need is to revive that influence in behalf of Israeli peace terms that do not abjectly humiliate the Palestinians and their more moderate PLO (Palestine Liberation Organization) representatives. Otherwise, apart from the justice of the Palestinian cause - a cause which is not going to disappear - it could become the excuse for the worst sort of terrorist activity.
For long-term peace the Palestinians and other Arabs have to be brought into the conciliation process, not alienated from it. It is not only proper but prudent for the US to make sure that its rock-bottom support of Israel as a friend and a secure state be combined with encouragement of moderating Arab influences.
Among further areas for adjustment between Haig policies and those of other administration figures are the Far East and Latin America. It should not be a matter of whose views win out so much as which are best for overall US interests in keeping with those of the nations affected. Here Mr. Shultz's reputation as a negotiator and team player of integrity should stand the process in good stead. The idea, as in modern problem-solving theory, should not be one side against the other but both sides against the problem that divides them.
Add to this a legacy of professional thoroughness from Secretary Haig, and US foreign policy could be on the way to the new unity heralded by that State Department spokesman - notwithstanding the loss of a secretary who brought so much more to his office than the skeptics had predicted.