Cassandra's Computer

THE world is full of prophets, most of them equipped with state-of-the-art computers.

They grind out their often-grim forecasts about the exact year the last tree will fall in the last rain forest. Or the exact month the ozone layer will be perforated over Nome, Alaska. Or the date -

mark your calendar - when life on Earth ends as a result of the greenhouse effect.

The latest prophecy deals with the anticipated diversity of the population of the United States in the mid-21st century. Census Bureau predictors have said the number of Americans will increase by 52 percent between now and 2050, with Hispanic Americans outnumbering blacks, Asian Americans growing at a faster rate than any other constituency, and all minorities adding up to a collective group about the same size as whites.

Unlike a lot of projections, this one offers a neutral, even benign vision of what's to come. If the multicultural scenario serves to stress the continuing need for ethnic tolerance, where is the harm in that? Still despite the need for planning, the vogue for peering a little obsessively into the future runs risks. There are at least two chief objections to an excess of futurology:

First, now that humming computers, not peeping wizards, are the agencies of forecasting, the dangerous presumption is that the ancient practice has graduated into a science. In fact, the score card has not improved all that radically. The most sophisticated prophets of only 30 years ago thought we would all be wearing disposable clothing and commuting to work in hovercars by now. If futurology games are treated as just that, they can be an amusing form of entertainment. But they need to be seen for what they are -

a department of ``virtual reality.''

Second, too much futurology is as diversionary as too much nostalgia. Worse, in the process of mistaking apocalyptic half-fantasies for facts, the public may resign itself to a sci-fi equivalent of predestination.

Confronted with all these models of things to come, what should a dazzled citizen do? The best response may be a healthy skepticism combined with the assurance that, if the present is properly attended to, one day at a time, the future should pretty well take care of itself.