BECAUSE FEWER Americans than ever are farmers, the original sense of Thanksgiving has faded and shifted a bit. As a farmer walks through his barns and sheds with their loaded bins at this time of year, he knows that all of his sweat would have produced nothing without the sunshine and rain sent at the right times by a benign providence. However much botany and agronomy the farmer may know, it's still impossible to bring in a crop after all of the hazards and turns of luck of the growing season without a deep sense of gratitude.

You might think that the same sense of gratitude would touch the other 98 percent of Americans who aren't farmers, as we walk throughthe aisles of supermarkets loaded with thegreatest and most diverse abundance that any society has ever enjoyed. But somehow that doesn't often happen. It's the paradox of prosperity: the more bountiful and reliable the food supply becomes, the less notice and gratitude it evokes.

At the supermarket, where fresh tomatoes will arrive all winter long from the Caribbean, the harvest is continuous and routine. Life, in its dinner-table aspects, has become vastly more interesting and healthier over the past several generations -- but it has also become less wonderful. The harvest has ceased to be a miracle. It follows naturally that Thanksgiving should increasingly seem to have less to do with either thanks or giving but become simply a jolly get-together opening the most convivial season of the year.

For some, of course, the season will benot convivial, but painful. To one largegroup of these -- the Americans serving far from home in the Gulf, and the families from whom they are separated -- the rest of us owe our thanks.

And to another group -- those here at home who are impoverished and unable to afford the bounty of the season -- we owe our help. Here in this wealthy metropolis there are plenty of people who live in ignorance, sleep on grates and die for want of rudimentary medical care. Society in general has been rather careless of these people in recent years. It has the resources to do a great deal for them, and that is certainly a reason for thanksgiving. There are now some incipient signs that over the coming months it will put more of these resources to work for them. The obligation could hardly be clearer.