THE GREAT PERIL facing President Carter is immobility - the political paralysis that seizes a man who has stared too long at conflicting choices. He has arrived at the point where every possible initiative in energy and economic policy seems to cut against some other cherished purpose, and every possible advantage seems to cancel itself out somewhere in the great equation. Guarantees of fuel to farmers aggravate shortages in the city. Decontrolling gasoline prices aggravates inflation - and for that reason, apparently, Mr. Carter has ruled out this quickest and simplest way to end the gasoline lines. Any serious attempt to produce synthetic fuels will jeopardize his hopes for a balanced budget. Mr. Carter's sharp analytical habit of mind keeps telling him that everything is connected to everything else.

This sense of stalemate is momentarily what accounts - in large part, anyway - for the current unpopularity of a president who has, in fact, done very little that is unpopular. But if he now concludes that, given his unpopularity, he can no longer afford to do anything at all that will make anybody angry - well, he is lost. Both he and the country will be infinitely better off if he draws the other conclusion - that his low standing in the polls liberates him to do, on a grand scale, what must be done.

The president is now beyond all the conventional considerations of placating his various constituencies; too many of them have already left him. As he establishes a course of action, he will find that most Americans understand perfectly well that one necessity often collides with another and not all choices are simple. Most americans also understand that circumstances change, and are less concerned with his past promises than he himself seems to be.

Where the president's inflation policy conflicts with his energy policy, it is clearly the energy policy that must have, for now, right of way. Much can be done to mitigate the inflationary effects of rapid fuel price increases. But amidst continual oil shortages, nothing can be done about inflation.

Where environmental standards conflict with power production, the protection of health has to prevail. Where those standards drive up production costs, the people who use the power can fairly be required to pay for it. To burn coal safely is largely a matter of adequate investment in the protective equipment.

The strategies to increase fuel supplies certainly won't work quickly, and perhaps some of them won't work at all. But if the country is going to have to live with less oil, it is essential for the government to demonstrate that every reasonable possibility is being pursued to relieve the dislocation and discomfort. The country is in a mood to experiment. Mr. Carter's office gives him a greater license for trial and error than he has seemed to believe. As Franklin Delano Roosevelt said of his first hasty farm bill, drafted in the dire distress of early 1933, "If the darn thing doesn't work, we can say so quite frankly, but at least try it."

If President Carter can now lay out a course of action that is comprehensible and forceful, he will find support flowing to it. The central requirement is, of course, a series of decisions that show a steady and unambiguous purpose.