MOST PEOPLE around the country are preparing to enjoy the abundance of the holiday season. Merchants may complain that Christmas sales are slow, but the wariness of the average shopper has less to do with any actual reduction in his purchasing power than with a slight feeling of guilt that comes from knowing that, for many Americans, good times are not just around the corner.

The most emblematic reminder of that distress is the national unemployment rate, which tells us that 12 million people, 10.8 percent of the U.S. labor force, are now jobless. If you're interested in more statistical detail, you can find out that in some areas the unemployment rate is more than twice that national average.

You'll also find that the duration of unemployment has been increasing -- 2.3 million people have been out of work for more than six months -- and that over the course of the year, perhaps a quarter of the labor force will suffer some unemployment. Two out of five of the unemployed will never get their old jobs back because those jobs have been permanently abolished.

Still, for most Americans, the statistics don't tell the story. Far more immediate reminders of hard times are the homeless people who now haunt almost every shopping center, business section and neighborhood. Even at the height of America's prosperity, these beggars-at-the-feast appeared now and then to remind the affluent that there were still dark corners in the nation's social structure. Now, however, such people -- the dispossessed -- are becoming harder to ignore, not only because they are more numerous but also because many of the newcomers bear a distressing resemblance to the family next door.

America's displaced persons now come in all sizes, shapes and colors. There are still the traditional winos and drug addicts. The bag ladies are a relatively newer phenomenon, but they are already a familiar part of the urban scene. Now they are being joined by displaced workers and their families who, having run through whatever savings and unemployment benefits they had, have been forced out onto the nation's streets and highways.

No one knows how many displaced people there are -- you can get estimates ranging from a half-million to 2 million, depending on whom you ask -- but there is no dispute about the fact that their numbers are growing. And there should be no dispute about the fact that this rich society has an overriding obligation to rescue these people from a fate that is unacceptable in America. This is not a country where families can live under bridges or in "cardboard cities" while the rest of us have our turkey dinner. In the next several days, we intend to come back repeatedly to this subject, by way of observing the Christmas Season, 1982.