There are only a few shopping days until Christmas, the Pentagon is buying at the rate of $700 million a day, and Randall Forsberg is talking peace on earth. If you think that makes the founder of the freeze movement an idealist, read on.

Five years ago, she initiated a movement with an idea: stop making nuclear weapons. The freeze was to be the first step to arms reduction. It was a shortcut through the defense debate to touch something every citizen could understand: the insanity of making more and more and more nuclear weapons.

But this month, sitting in her Boston office at the Institute for Defense and Disarmament Studies, Forsberg admitted that her shortcut was not a victory trail. Yes, more than two-thirds of Americans support the idea. Yes, the freeze organiations raised abut $2.6 million and put 20,000 volunteers into the past national election. But in the biggest arena of all, the presidential campaign, their man and their issue lost.

Forsberg blames only part of this defeat on the candidate. She says, "Mondale came across as a paler version of Reagan. Mondale had no vision of a different, a fundamentally different future. . . . What you got was the same idea as the Republicans have had for a long time, which is that . . . we're going to have a permanent technological arms race."

At a deeper level, Forsberg says the freeze failed to have a wider impact for one reason. It never addressed the underlying belief that nuclear weapons prevent war, conventional war, between the superpowers.

Many argue that it is only the risk of nuclear warfare and nuclear winter that prevents another World War II. If this is true, says Forsberg, if fear of conventional warfare is the motive for the nuclear arms race, then the only way to halt that race is by reducing the risk of war itself. So much for shortcuts.

Forsberg is at once an elitist and populist, an academic and political organizer, the head of a think tank and the winner of a coveted and cushy MacArthur Foundation grant for "exceptionally talented individuals." Soft-spoken and committed, she believes that in its second five years, the freeze movement will give birth to a wider peace movement whose goal is nothing less than changing attitudes toward the use of force.

"The main point is that as long as people use force as a tool of power they can't trust each other and they rely on nuclear weapons instead," she says. "So the connection is you can't get rid of nuclear weapons unless you get rid of the interventionary use of conventional force."

As Forsberg spells it out, the first step is to stop U.S. and Soviet interventions in the Third World. The second step is to make deep cuts in conventional forces. The third and hardest step is to get the Soviets to give up their hegemony over Eastern Europe.

If this agenda sounds like the wishful politics of folksinger peaceniks, the level- headed strategist behind it understands. At the beginning, she says, "the freeze was also a pipe dream." This is not, Forsberg admits, a five-year plan but a 50-year plan or a 100-year plan.

How do you plan for a 100 years' war against war when nuclear winter is on a hair trigger?

"Many people will say this is hopeless, this is too much, this is too big, it's too hard," admits Forsberg. Indeed, the movement will continue to push the freeze directly with a comprehensive freeze bill and a test ban. But at the same time she is convinced of the need for a wider approach.

In fact, her strongest selling point is with the opposition. The people in charge of current defense policy have no alternative. Under their leadership, she says, "It's going to go on forever. We're going to spend $300 billion a year (for defense); we're going to have 25,000 nuclear weapons; nuclear weapons are going to spread to more and more countries. . . .

"All I'm talking about is that people understand what's being done in their name, what they're going along with. That people look at their own feelings about the way the world works, about human nature, about warfare, and look around them at their neighbors' feelings."

In Randall Forsberg's life, peace on earth is more than a season's greeting.