When the Outs are being creamed by the Ins, a bold and unpredicted move may do as much to receive the spirits as a shrewd one. So it is that the Americans for Democratic Action -- the nation's oldest, largest and currently hopping-maddest liberal organization -- has chosen Robert Drinan as its new president.

No one on the thinking Left -- from Irving Howe and his humane socialism to Rep. Cardiss Collins, the Illinois Democrat and bright spirit of the Black Caucus -- has a background that is close to matching the activism and scholarship of Drinan. He is a man of hyphens (priest-professor-lawyer-politician-writer-traveler) whose loyalties to liberal ideals have not been hyphenized by the times into neo- or post-liberalism.

Some of Drinan's loyalties showed the other evening when he told the delegates to ADA's 34th convention that it was an occasion to remember the advice St. Ignatius Loyola gave to his followers in the 1550s when the Society of Jesus was founded: Pray as if all depended on God, but work as if it depended on us.

The ADA can be expected to leave the praying -- or at least the public look-how-pious-I-am-kind -- to James Watt and Jerry Falwell. But work is what it is ready for, especially now when its ranks have been increasing -- since January -- by 1,000 members a month. "Ronald Reagan," said Rep. Barney Frank (D-Mass.), an ADA blueblood, "is doing a lot more for us as an enemy than he ever did as a member."

Drinan's re-emergence into public life is a sign for unbelievers that God's sense of humor is divinely intact. Elected to Congress for ten years, Drinan found himself out of office on the one-pope one-vote rule. But the joke is on John Paul II. He was able to order priests out of politics, but he couldn't get politics out of priests.

Drinan the Jesuit is jesuitical about his new post. He expects no trouble from the Vatican because "the ADA is not a partisan organization. It is not affiliated with any political party. The papal decree, or the ruling canon law, applies to priests only in elected politics."

Drinan leaves his subtle side for Roman politics. For American politics, he unbosoms his mind in a frank description of the Reagan crowd: "a small group of extremists who have taken over our country." It is a time to be "frightened by their devastating assault on all what we hold sacred."

Conventional wisdom says that a test of strength is the last thing that liberals need right now. If they didn't understand that they were wiped out by the elections of 1980, then the message was sent again, via two-by-fours this time, in the budget vote two weeks ago.

Drinan is aware of all this, but he argues persuasively that the Reagan-Stockman-Laffer style of conservatism can do nothing to root itself because its subsoil is weak. Nothing will hold.

"There is no reason why we have to turn our back on the poor," he says. "There is no reason we should take the social programs that passed overwhelmingly by large margins all through the years and cut them back by 25 percent. Even in the name of the ideology or the economics of this administration, it's not going to cure inflation. They are transferring virtually all of this money from the poor to the Pentagon. Federal spending is not diminished.The budget will not go down."

That's a forecast worth remembering in the dark days ahead. But in skewering Reagan's policies, Drinan is sufficiently seasoned to know that mere thunder from the Left isn't enough. The claps may not be heard, with the audience having moved rightward. Many liberals are only now figuring out what has hit them, though groups like ADA were warning three years ago that even Jimmy Carter "has given us conservative domestic policies and Republican Party economic programs."

Drinan asks: "Is it not unbelievable that under Reagan some $40 billion is being transferred from the poor to the Pentagon? It may be that this fact is so unbelievable that people have not yet been able to believe, much less comprehend, it."

Drinan needn't worry: The comprehending is about to happen. His immediate challenge is to rally liberals back to their traditional combativeness. Reagan and the New Right aren't defeating liberals. It's worse: They are trying to tame them.

Almost as though papal infallibility were involved, Father Drinan's return to national prominence is timed perfectly. He is telling the liberals: Work as if it depends on us.