WHEN WE TALK about history in this town, usually -- and oddly -- we are talking about the future, not the past. As in: History will probably say that . . . etc. History is our out, the highest court of appeal, the repository of our eternal hopes. History will vindicate us, we think; people then -- as distinct from the dummies now -- will know what we were trying to do and what we did do and they won't think we were such a bad or useless lot after all. Presidents, habitually rendered politically terminal cases after a period in office, must place their trust in the clarifying and rehabilitating powers of the passage of time. Look at Truman -- a departing, mussed-up president must think -- look at Eisenhower, look at Johnson, look at (even), yes, Nixon .

We thought of this while watching a somber, matter-of-fact Jimmy Carter the other evening bidding his farewell to the American people -- the same American people who had sent another melancholy president packing four years ago to make way for him. The supposition that he will get a better judgment in the future is bound to be Jimmy Carter's solace now. And certainly in the themes he chose to stress and thus to identify as the central purposes of his administration, he was reaching for that larger, long-run judgment. This president who, maddeningly, on other momentous occasions (e.g., his renomination) had consented to give tedious laundry-list speeches, this time chose to speak of his efforts not in a lot of little realms but rather in a few gigantic ones: those realms of policy and behavior that concern our very physical and spiritual survival.

You can fault the president's SALT negotiations and the accords he brought home from Vienna for ratification; you can fault the execution of some of his administration's regulation-generating environmental policies; you can fault the application of his human rights doctrine in various places. Some part of all of the above came to grief or came to naught, and it is not obvious that any particular set of approaches to these questions is the best or only means of achieving the transcendentally important purposes involved. But the president was right to dwell on these few themes -- right politically and right from the point of view of his audience.

We say he was right politically because clearly Mr. Carter, hitting hardest on arms control, environmental protections and the human rights campaign, had in mind areas in which he expects to look good in comparison with his successor over time. Whether he will or not we do not know, but Jimmy Carter was laying claim to the territory Wednesday night. And by not seeking too much more he helped his audience too, giving them at least one overall vision of what their government had been about for the past four years, a way, if they choose, of beginning to think about and place the Carter administration. The president lifted the discussion, for the moment anyhow, above tactics and personalities and follies and chance (all of which have much to do with a government's success or lack of it) and said, in effect, this is what it was all about . . . this is what I had hoped to do. It was a dignified and poignant moment.