Every time this country gets around to considering what to do about its postal service, we try to lean in two directions at once.

First, we lean toward to the idea that the post office is a public service with a great many special constituencies that ought to be subsidized.

Then we lean toward the idea that the post office is an enornous business enterprise that charges the consumer like any other business enterprise and ought to turn a profit on the job.

Which is it? If it's a service operating strictly for the public's convenience, then we should keep Saturday mail delivery, retain all those post offices and postmasters in remote hamlets and restore the lower rate for magazines, which complain that the current rate hurts too much.

If, on the other hand, the post office is a business, trying to perform the duty of business, which is to turn a profit, then we should cut out inefficient outlets, recognize the fact that Saturday has become a national holiday and make the magazines pay their way.

We can never quite seem to make up our minds. The latest example of our fickleness if HR 7700, which has passed the House Committee on Post Office and Civil Service and may be voted up or down during this season. Only six years ago, the Congress decided that the post office should "pay as you go." The new bill makes an abrupt turnaround.

It would add $1.5 billion to the present subsidy to ensure Saturday delivery and the maintenance of remote village post offices. It would abolish the board of directors established by Congress back in 1971. It would restore the Postmaster General to the list of presidential appointees and would make Congress itself the ultimate arbiter of all rates and of all service changes.

In short, it would put the post office right back into politics, which is where it was before 1971. Mail rates and services would be subject to lobbying, and soon magazine publishers would undoubtedly rest more comfortably at night.

Actually, the post office hasn't done too badly as a "business." In 1973 it very nearly broke even. But in 1974 a recession hit, mail volume dropped and the deficits became enormous again.

That's why the present post office, operating as a "business," wants to trim services. By so doing, the board of directors foresees a break-even point just ahead, particularly since mail volume is now on the increase again.

Operating as a "business," the post office has also cut the number of its employees substantially and has established a pretty good record for efficiency, if efficiency can be measured by the ratio of number of employees to pieces of mail handled.

But the "business" is still subsidized to the tune of $1 billion a year, not counting deficits, and Congress still gets most of its complaints from constituents who are unhappy about late mail delivery and about rumors that nice old Mrs. Grundy will be out of a job when "they" close up the post office at Mountain View.

So the pendulum now appears to be swinging back toward the old system of giving everybody what anybody wants, including President Carter, who has suggested that he would like very much to have the power to appoint the next Postmaster General.

If history is any guide we will run that way fora while, after which there will be a move to put the post office back on a businesslike basis, put some businessmen in to run it and make the thing pay for itself. Somebody will ask, Why can't the public pick pu its own mail at designated neighborhood stores?

By that time Myron A. Wright, chairman of the board of Exxon, whom Congress brought in to serve as chairman of the board of the U.S. Postal Service, will be back at his own business, doubtless thinking up ways to persuade the customer to pump his own gasoline.