THE APPOINTMENT of Charles W. Duncan as Secretary of Energy suggests a strange reading of the job immediately ahead.Mr. Duncan has a strong reputation as an administrator and technician. He appears to score well on the new standard of loyalty and, according to advance reports, will do as he is told. But who is going to tell him?

It's quite true that his prodecessor, Jamrs R. Schlesinger, has become a political liability to the president. It is in the nature of that job that it uses up people rapidly. Mr. Schlesinger has been inconviently right on a wide range of policy issues where the right answer is unpopular. Most recently, he has favored decontrolling gasoline prices and raising the federal gasoline tax. He is, incidentally, firmly in a line of presidential energy advisers, stretching back to the Nixon administration, who urged higher gasoline prices and paid for it in political standing.

But it is also true that Mr. Schlesinger has never found a way to respond persuasively to the social concerns and regional anxienties that higher energy costs generate. He has become a liability to the White House because, to a great many voters, he seems too much the voice of the computer. He has had trouble making his logic clear to people who are poor, or who are frightened by unpredicable price jumps, or who live out at the ends of the pipelines. The next secretary would be, in an ideal world, a person capable of seizing the Schlesinger logic and presenting it in comprehensible and compelling terms to those Americans who are not economists and engineers. Mr. Duncan does not look like a candidate whose background prepares him for that job.

Instead, the choice of Mr. Duncan indicates that the president wants a secretary who will devote himself to the unquestionable administrative chaos within the department. Chaotic administrative chaos of the counts against Mr. Schlesinger, but it's the least of them. Welding together a new department out of many established agencies, with devergent political interest, always takes longer than presidents Expect. The Department of Health, Education and Welfare was the country's standard for internal confusion for fully a decade after it was established. The Energy Department's lapses are serious, but they are conventionally, and properly, the concern of people at the second and third levels rather than the secretary.

The implication of Mr. Duncan's appointment is that Mr. Carter intends to direct energy policy from the White House. But how? He cannot do it all himself and his staff cannot do it, yet his recent speeches have set in motion programs requiring the most skillful and forceful political guidance. Mr. Schlesinger's departure had become inevitable. But in replacing him, Mr. Carter does not seem to have addressed the central necessities of a strong and widely supported energy policy.