'New ideas' - are they an idea whose time has come?

DOES anybody have any ''new ideas''? The plaintive question threatens to become the issue behind all the other issues of the 1984 campaign. Rejecting the Republican Party as the condemned property of the 19th century, the Democrats have declared themselves the official party of ''new ideas.'' But now civil war has broken out among the Democratic candidates as to who really has the ''new ideas.''

Gary Hart may run on the presumption that he is the candidate of ''new ideas.'' Yet the other candidates are saying that, whenever a Hart ''new idea'' can be pinned down, it turns out to be practically, well, Republican.

The fact is, ever since the New Deal celebrated its 50th anniversary, the old liberalism suddenly seemed too old to boast about. But in spite of book-length manifestoes from younger Democrats - like Hart, like Paul Tsongas - a new liberalism has not yet emerged.

Everybody can, and does, set up a ''new agenda.'' We must clean up the environment, control the arms race, and so on. But when what-to-do sidles up to how-to-do-it, a great silence falls. ''New ideas'' are in danger of being reduced to just part of a politician's image.

A shortfall of ''new ideas'' is hardly restricted to politicians. Futurologists profess to specialize in ''new ideas.'' But rather than ''new ideas,'' they tend to give us scenarios - ''The Third Wave of Megatrends,'' to mix up our best-selling Alvin Toffler and John Naisbitt. One is provided with the demographics and high-tech profile of a projected ''Information Society'' and invited, somewhat uncritically, to adapt.

The implication is that ''new ideas'' will more or less automatically pop up as ''the technology of the day extends and enhances our mental ability,'' to quote one futurologist. Meaning, of course, the computer.

What would we all do without computers and our naive hope that their ''artificial intelligence'' will somehow generate ''new ideas'' for us? Presto!

''New ideas'' must come first. ''New ideas'' come before everything else and govern the course of everything that follows. Without ''new ideas,'' the new technology will be inclined to produce superbombs and supertoys.

Indeed, nothing so exposes the lack of ''new ideas'' as the self-proliferation of high-tech gadgets.

Once upon a time somebody invented the microwave oven so that everybody could have more leisure to - you know - think up ''new ideas.'' Now somebody has had to invent a radiation detector to sound the alarm if any microwaves are leaking out.

Another indispensable gadget will weigh the goodie you are slipping into the oven and give you a digital readout on exactly how many calories it contains as well as a count of vitamins and nutrients. Then, when you have enjoyed your goodie, you can step on a ''talking'' bathroom scale that will tell you in a sad synthesizer voice how overweight you have just become.

Are these ''new ideas'' or just novelties?

Our biologists introduce more and more sophisticated descriptions of how the brain works as they theorize about the process of thinking up ''new ideas.'' Our engineers devise electronic circuits capable of ''outthinking'' poor nonsynthetic intelligence. But where are the ''new ideas?''

''New ideas'' reconstruct our moral choices - reshape our very lives. ''New ideas'' show us possibilities we had never dared to see before. ''New ideas'' make us profoundly wish to be wise, to be good.

The national preference is to act rather than to reflect. But all at once, as Republicans and Democrats - as people - we Americans seem to feel trapped between our old went-thataway assumptions and our not-yet ''new ideas.'' Why, we're almost prepared to admit that, without ''new ideas,'' public life is power run amok, and private life is a cycle of fad-and-chic.

In 1984, this can pass as a ''new idea,'' if not an American heresy.