An odd notion of Ronald Reagan, the Great Non-Communicator, has taken root -- shallowly, one trusts -- under the very roof of the White House. There one can hear the admission, accompanied by sighs and shakes of the head, that President Reagan has indeed and unfortunately failed to spell out his foreign policy goals, and that he needs to make a major address to accomplish that job.

Hard on the heels of this confession comes the rather defensive-sounding explanation that the president does, of course, have good reason for having left a gap -- to get the major parts of his economic plan out of the way first.

Talk about confusion of form and substance. One can forgive the town's once and future speech writers for suggesting that the process of preparing a Major Foreign Policy Speech, in which a president generates the basic themes for his aides to elaborate, refine and thrash out, itself electric and stately, virtually the crowning exercise of presidential leadership. But how can savvy aides close to Reagan be ululating in this fashion?

Say what you will about the Reagan foreign policy, it seems to me insupportable to say that we don't know what his goals are. What do we know better? When has a president ever communicated more clearly -- from where it counts: the heart, the hip -- where he wants to go in the world? Just who is in doubt? We may have known more about Ronald Reagan's international ambitions before his presidency began than we knew about Jimmy Carter's when his presidency ended.

Actually, to know Reagan's policy we do not have to rely entirely on the signals he has been sending for the last 15 or so years -- as constant, consistent and reliable as these have been. In his nearly five months in the White House, his administration has taken numerous specific steps around the world. We do not know all the particular steps he will take from here on in and how they will match up with each other. But Don Oberdorfer of The Post connected the dots the other day and came up with "an accretion of tactical decision [adding] up to a policy, if not a grand strategy." Quite so.

Some people complain, or allege, that the administration is still groping for a grand design, or is still groping for lack of one, but that is the last complaint I would make. My complaint is that Reagan has a grand design, one he shaped and firmed up in his years in the wilderness, and that he is not so much testing it against reality as he is imposing it piece by piece as he goes, without taking due care to see if it fits. Events have forced him to take some detours -- the grain embargo -- but the design seems no less operative for that.

In the circumstances, what possible advantage can there be for Reagan to let it all hang out in a big foreign policy speech? He already knows where he's going, as do the aides he shows the most confidence in. Those in the bureaucracies and the embassies who don't know have little to beef about. Precisely because Reagan has a design in his head, he has a special need for tactical flexibility, and he serves it up to himself by not saving everything at once.

Even those of us who are wary of his design can be pleased that he unfolds it slowly and gradually. That gives events and contrary arguments a chance, whatever it may be, to make their pragmatic mark.

As for Reagan's determination to keep foreign policy from distracting the administration's and the country's attention from the economy, he is completely right. One does not have to share his confidence in his economic plans in order to believe that 1) he has reason to establish his credibility by holding to his repeated pledges to make revival of the economy his first domestic and foreign priority, and 2) he can accomplish little that is important and lasting in foreign policy unless he makes headway in his mission of economic repair.

That goes whether you think that he deserves a chance to show his economic program will work, or whether you believe that his program, since it's going to be largely passed anyway, needs to be seen to fail so that something more promising can be tried.

Reagan's situation recalls Eisenhower, another president who enjoyed substantial public confidence even before he was elected and started articulating policy. We know better now than then that Ike nursed his popularity, and his options, by mumbling. This would seem to be a good model for Reagan.