MOST OF the people now receiving the Social Security minimum benefit are not the sort who can launch massive letter-writing campaigns or work ther halls of Congress. Perhaps as a result, an administration proposal eliminating the minimum benefit for people with low earnings records moved with little notice into both the budget bills being reconciled in a Senate-House conference.

Now one group among the 3 million people potentially affected has been heard from -- about 14,500 nuns and male clerics belonging to religious orders.Last week, spokesmen for the nuns caused a good deal of squirming among members of Congress on both sides of the aisle, lending strength to efforts by House Majority Leader James Wright and others who are sponsoring a resolution -- scheduled for a House vote today -- calling for retention of the minimum.

The appearance of the nuns and male clerics came as a surprise to almost everyone. Under the normal conventions of Social Security and other social insurance programs, members of cloistered religious orders wouldn't be eligible.Since they have taken a vow of poverty, they receive no wages and pay no payroll taxes, relying instead on the orders they have joined to provide them with room, board and other necessities. Amendments to the Social Security law in 1972, however, allowed the orders to make contributions on behalf of their members on the assumption that the benefits they receive have an income value of about $100 a month. The Social Security benefit formula is weighted to give a very high rate of return on low earnings, but in this case the taxes paid are so low that the nun's benefits would be very small without the minimum floor. They would, however, retain full eligibility for Medicare.

Spokesmen for the religious orders pressed for a special exemption from the minimum-benefit termination. They argue that their members do not have available the welfare alternative suggested by David Stockman as the proper recourse for the needy, since they have taken a vow of poverty. Since welfare and Social Security are, as far as we know, paid in the same currency -- and since welfare benefits are typically set so as to make sure that recipients stay in poverty whether they want to or not -- this seems a curious argument. Moreover, since other minimum beneficiaries actually sacrifices income to gain coverage while the nuns and clerics did not, special treatment is hard to justify.

Putting a spotlight on the religious orders has, however, drawn useful attention to the plight of all the elderly for whom adjustment to a sudden reduction in circumstances will be even more difficult. While ending the Social Security minimum for future beneficiaries can be justified -- under current law, the benefit is already scheduled for a gradual phase-out -- abruptly changing the rules for people already relying on the benefit does not. Of the group at risk, 1.5 million are over the age of 70, close to 100,000 are over 90. Two million stand to lose an average of 40 percent of their current benefits and, according to the Congressional Research Service, 800,000 are potentially without alternative sources of income. Gradual disclosure of one sad case after another caused by an almost unexamined budget decision is not a happy prospect for Congress or this country.