LISTENING TO Jimmy Carter talk about arms control - especially about strategic nuclear weapons - is a novel experience. He does not sound like other Presidents. Mr. Carter is clearly at east with the subject; he is also clearly preoccupied with it; and he projects an unaccustomed sense of possibility, of optmism even, in his public discussions of the U.S. Soviet talks. The question is whether his expressions have an institutional life outside the Oval Office. Are they proposals likely to be the basis of successful negotiations with the Russians?

At his press conference the other day the President was evidently pushing on the Russians in several areas. He let it be known that he would like to take the cruise missile/Backfire discussions out of the SALT II bargaining and save them for another day - a proposal the Russians have rejected in the past. He alluded to the troubling aspects of the Russians' development of mobile installations for their SS-20 missiles, suggesting that if they halted work on these mobile missiles, the United States might be inclined to forgo its own. He reiterated his wish that the Russians would agree to a ban on "all nuclear testing," saying that he could evision some arrangement of this kind that would permit them to use nuclear explosives, if they wished, in a particular river-diversion project.

It was an extraordinary performance. There was something in it to gratify all sides in the heated domestic debate over national security and strategic arms. Taken together with his strong defense of Paul Warnke, his nominee to run the arms control agency and conduct the SALT talks, Mr. Carter's commitment to a comprehensive ban on nuclear testing was bound to please the more disarmament-minded among his constituents. Likewise, Sen. Henry Jackson and others sharing his outlook were pleased by the President's effort to remove the cruise missile/Backfire issue from this round of strategic arms talks.

Still, this kind of picking-and-choosing support that the President is acquiring is possible only because he has been presenting a kind of nuclear-arms smorgasbord to those concerned. That is different from a policy or a consenus or a program that has been subjected to the discipline of government. Such a discipline will, in the first place, mean that the various parts of the Carter program fit with each other and that they will have been fashioned, argued about and - in some measure, at least - approved by the various scientific, military and diplomatic bureaus best qualified to judge the merit and workability and impact of any new agreements.

Since the Carter team that would make the relevant judgements is not even in place yet, the President's various statements cannot represent glimpses of a genuine strategy that such a team has worked out. Nor do certain of the objectives he has publicly espoused strike us as likely candidates for acceptance by the Soviet Union. Since the Russians have already got much of what they want in nuclear testing agreements worked out during the Ford years, for example, and since Mr. Carter evidently intends to go forward with the signing of these agreements, it is not obvious why the Russians would be interested in the more rigorous ban he offers them now. So, welcome as the President's preoccupation with these deadly matters may be, his statements so far really tell us very little about his ability ro reconcile the divergent elements of his arms control position or about his prospects for negotiating a useful and reliable deal with the Russians.