An argument is brewing over proposals to abolish the Private Express Statutes, which give the Postal Service a partial monopoly over the delivery of letter mail. Under these proposals, the responsibility for mail delivery would shift from the federal government and the Postal Service to the invisible hand of the marketplace and private companies. The premise is that men and women driven by the profit motive can deliver all the mail more efficiently, and at a lower cost, than the Postal Service.

This is nonsense. Certainly, a private business can make a profit by delivering some mail at a lower price in certain easily accessible, densely populated areas. But the consequences for nationwide postal delivery would be disastrous. The universal postal system as we know it today would be destroyed.

Scores of private postal operators would spring up in populated areas to offer delivery services for local mail. As smart businessmen, these operators would limit themselves to high-volume, low-cost areas, such as Wall Street and similar downtown business districts. They simply would not bother to deliver mail to high-cost areas, such as rural America, less densely populated suburbs and poor inner-city neighborhoods. They would also not be likely to offer postal customers conveniences that we have come to rely on, such as window service.

No wonder mail service by some of the private operators would be less expensive --they would only provide low-budget delivery service in high-profit areas.

The consequences for the Postal Service would be ominous. This "cream-skimming," as it is called, would take a considerable volume of mail away from the Postal Service. The cost of providing service to rural communities, center-city neighborhoods and other high-cost areas would skyrocket due to the loss of urban business volume.

The Postal Service would either have to raise its rates dramatically or, more likely, look to Congress for the lost revenue. The mailers or the taxpayers would be left to bear these costs. If the postal monopoly were eliminated today and the taxpayers subsidized delivery in unprofitable areas, the cost of delivering mail to those areas would add $100 billion to the federal deficit by the mid-1990s.

The consequences for the American consumer would be worse, for we would have a balkanized postal service with many delivery systems. In addition to first- and second-class mail, we would have first- and second-class communities.

Where would the buck stop under such a balkanized system, and who would accept the ultimate responsibility for the many services the public has come to expect:

* For forwarding mail when it has to go to another part of the country?

* For protecting the privacy of the mail?

* For protecting the public against fraud and false advertising?

* For handling the huge volumes of foreign mail?

* For ensuring uniformity of service?

To force the American people to depend on the services of private carriers is to ask them to play Russian roulette with their personal correspondence, their bills and their financial transactions.

It would also impose upon them a crazy-quilt system of rates that a genius couldn't keep in his head. The public has trouble enough calculating zoned parcel post rates. Think how difficult it would be to calculate the cost of mailing a letter from New York to Louisville to a rural route outside of Paducah, Ky.--via three different carriers, or two carriers plus the Postal Service.

The continuation of a nationwide system is a clear benefit to the American public and to American business. In putting a first-class stamp on a letter, a mailer in New York City or Biloxi or Honolulu can reach anyone in the 50 states from the mailbox on the nearby street corner. In a world without the Private Express Laws, the Postal Service simply could not offer such service to everyone at a relatively low, uniform price.

The Private Express Statutes exist to protect the American mailing public. They enable the U.S. Postal Service to be the most efficient postal system in the world. Abolition of these laws would be costly to our taxpayers, chaotic to our systems of commerce and communications, and a reversal of a 200-year policy that mail delivery in our democracy is a basic and fundamental service provided to the people by the government of the United States.