The trouble with liberals in the 1980s is that they seem hopelessly out of ideas, social as well as economic. They know that they are unhappy with Reaganism, and they also know that a return to pre-Reaganism is no solution to anything.

They acknowledge that many of the programs that Reagan has axed were not working very well in the first place, and some of those that were working reasonably well had become unacceptably expensive. They insist that the programs should not have been cut unless the administration had other, more effective and efficient programs to put in their place. But the liberals themselves have not come up with proposals for reasonable substitutes. They simply don't have the ideas.

Jesse Jackson has had a different problem. His troubles have not come from a lack of ideas but from a disinclination to follow through on them. He fairly oozes ideas: some of them as old-fashioned as his notion that black children need to spend less time agonizing over racism and more time taking advantage of the advantages, educational and otherwise, that do exist; some as insightful as his thesis that blacks face problems of both caste and class, and that their salvation requires attacks on both fronts.

The criticism of Jackson, founder and head of Operation PUSH, has been that he delights in giving birth to ideas but has little interest in nurturing them.

No more. His latest notion is that corporate America must be induced to treat black America as it treats any other underdeveloped nation in which it wants to do business: that is, to engage in aid as well as trade.

So far, in a campaign that started nearly two years ago, PUSH has signed agreements with Coca-Cola and Heublein and, last Saturday, announced a $61 million agreement with 7-Up. Other civil rights organizations are taking a hard look at the PUSH idea, and indeed the NAACP already has announced a program it calls Fair Share.

Jackson's idea is that black America's focus on government assistance and job creation has been shortsighted. His goal is not full employment but full development for the black community. The 7-Up agreement, for instance, includes commitments to use black banks, insurance companies and advertising agencies as well as to increase the number of black executives, including an additional member of the board of directors.

"If you are an American corporation that wants to set up an operation in, say, Nigeria, you have to go in with a development formula," he said in a recent interview. "You have to promise more than jobs and an ad in the souvenir program at the annual banquet. When you go into Nigeria, X amount of the ownership must remain there. You can't say you'll hire all Nigerian workers but have only white executives, that you will use only British banks. It's the same in Mexico --in any developing country."

But in black America, he says, business has been a one-way deal. "We bought $12 billion to $14 billion worth of automobiles last year. Chrysler has used our labor, our purchasing power and (through federally backed loans) our tax dollars. They had $7.5 billion in sales and $3 billion in procurement contracts alone. Less than $20 million of that trade was with blacks."

Jackson, who earlier this month began trade negotiations with the auto industry, says black America's fair share of trade with the Big 3 would be $5 billion a year.

Jackson's leverage in his corporate negotiations is what he terms a "withdrawal of our enthusiasm" for the corporation's product: in effect, the threat of boycott.

"I don't think of it as a boycott," he said. "I prefer to think of it as a legitimate tool to keep corporate America from boycotting black America. They have been boycotting black executive talent, black attorneys, black CPAs . . . and black trade."

But shouldn't employment be black America's priority?

"Employment is inherent in development," he argues. "The Marshall Plan was not a plan of full employment, but it produced full employment. Full employment by itself is not enough. We already had that --on the slave plantations."