John McKnight, Northwestern University's "urban philosopher" with a story for any occasion, tells a story that just might make you take a new look at the way we look after poor people -- which, of course, is why he tells the story.

It was during World War II, this particular story goes, and the Japanese had captured the coastal towns of New Guinea. The Americans, in a countermove, parachuted commandos into the interior mountains to harass the Japanese from the rear so they wouldn't be able to run their ports.

The military value of that move is not what interests McKnight. His fascination, he said in an interview with Chicago magazine, is with what followed.

"These Americans came down in parachutes, and they cleared away the trees, and then their cargo planes dropped boxes full of the most wonderful things these natives had ever seen in their lives: food, clothing, guns -- everything."

In short order, the entire economy of the natives came to be based on the cargo drops. But then the war ended, and the planes stopped coming.

The people, convinced that they must have offended God somehow, began building huge mock airplanes out of sticks and clay, finally developing what came to be called "cargo cults." It never occurred to them that the airdrops were not primarily for the New Guineans but for the American military's own purposes.

McKnight is persuaded that we are doing something frighteningly similar by the way we seek to help America's poor. That is, we catalog needs, and then undertake to supply them, taking no notice of the costs -- neither the needlessly large governmental outlays nor the debilitating effect the process has on those we try to help.

He isn't the first observer to make the point. Even during the days of the War on Poverty, a number of liberal thinkers said (simplemindedly, we thought) that what poor people needed was not programs but money. More recently, Reagan administration conservatives have talked about "cashing out" programs ranging from food stamps to public housing.

But McKnight, being a storyteller, makes the point more dramatically. Would you, he asks, take a job that offered $10,000 a year, but only $3,500 in cash -- the rest going to pay teachers, doctors, and social workers? He doubts it. But look at what we are doing:

The money New York City spends on its low-income population amounts some $7,000 per person per year, or about $28,000 for a family of four. But only 35 perecent of that money represents income. The rest pays for social services.

McKnight is not just being cute. His point is that a focus on deficiency tends to produce just that sort of result. A focus on capacity, he believes, might cost far less and accomplish a good deal more.

He has a story to support that notion. A Chicago neighborhood organization, attracted to the "capacity" idea, decided to ask residents of a low- income neighborhood not what they needed but what skills they possessed.

"After they had visited the first 80 apartments and talked mostly with women," he said in a recent speech here, "they looked at the list to see what kinds of work experience people had. The most common was some work in a hospital, some work in a nursing home, or some work in home care.

"Nearby -- maybe four blocks away -- is a moderate, middle-class neighborhood. So they put an advertisement in the newspaper saying "Health Care Workers Available," because they had 50 people who thought they had that capacity. The phone rang off the wall. In fact, within one week, all of the people with those skills were employed within eight blocks of where they resided. These women have now formed a club that has become the basis for mutual support and planning to deal with the child-care issue. They are also developing the group into a cooperative business, and they are planning to use their purchasing power to support the development of a few new businesses in their community."

The "capacity" approach focuses on tapping the ability of poor people to become producers. The "deficiency" approach teaches them, like New Guinea's pitiful "cargo cultists," to become mere clients.