THREE YEARS ago, Dr. Benjamin Spock was a defendant in the first conspiracy trial involving protesters against the war. Today he remains gleefully absorbed in urging political dissent.

Interviewed in Boston on April 15, Spock is currently stumping American colleges and universities on behalf of the Civil Liberties Legal Defense Fund (no relation to the Civil Liberties Union).

This is his third year working for the Fund, which has aided draft resisters, GI's, "conspirators," and Black Panthers. "The relatively radical causes of relatively radical people," according to Spock.

"I like to think I'm influencing middle-of-the road students," he says, "but if I'm not doing that, at least I'm raising good money."

He attributes the crowds he draws to "the simple fact that I've been indicted and convicted," referring to the "artificial success conferred on me by the federal government." Originally found guilty in the 1968. Boston Five conspiracy trial, Spock was later acquitted on appeal.

This time around, he is concentrating on the theme of dissent, he said. "The war in Vietnam was my excuse for dissent," he says, but he stresses the importance of action on many issues. "The first Harvard and Columbia strikes are good examples of how a very small minority can swing a majority to their support.... What is this law and order that the authorities are pulling to their support-what do they mean, telling black people they can't riot?" he asks indignantly.

He sticks to this point. "What you have to say to people-and it's more effective to say it to young people-is that justice is the most important thing. People have to help the law catch up with justice." His examples from history include the women's suffrage movement. "For heaven's sake, nothing was accomplished until women started smashing windows-society matrons, knocking the heads off statues."

Speck described a "profound change" of mood on university campuses in the last two years. "Two years ago in a community college, I would get a smattering of hand claps, then a deluge of hostile questions. Now it's hard to get anyone to even present the opposite point of view." Rarely invited to a Southern school two years ago, he has now spoken in every state in the South where even his expressions of support for the Panthers are applauded.

Spock is clearly applause-conscious, mentioning the audiences' response several times in the interview. "These standing ovations," he admits frankly, "I just love it."

ALTHOUGH an avowed admirer of young people, "especially idealistic young people," Spock confessed that he was disappointed at how easily some of them give up. "They're much quicker to arrive at a radical analysis of things but then they shrug their shoulders and say 'oh I tried that and it didn't work,' " he said. "It drives me absolutely frantic," he added.

He does not think the antiwar movement has lost its momentum, but simply that "you can't keep up a fiercely visible resistance 100 per cent of the time."

Spock is optimistic about the Left's ability to expand its traditional class base. Opposition to the war, he said, has been "definitely a class phenomenon," but remarked that now community colleges and high schools, "even in working class neighborhoods," are being politicized.

With regard to the relationship of the white left to the black movement, Spock said, "I think blacks who have become politically aware just can't stand white people. I don't blame them, but from a realistic point of view, I hope we can work together. Obviously, black people aren't going to get justice unless they become more radical and when they do that, they're eradicated. I think the lesser evil is to keep up the pressure."

As to his own political stance, Spock classifies himself as "somewhere between liberal and radical-in this stage of American history, militant and an activist." He is opposed to violence in most circumstances on the grounds that it "wins damn few people to your side."

He hastened-characteristically-to qualify this judgment, however. "I don't want to imply that I'm morally superior to the Weathermen-I'm certainly not as courageous and maybe not as sincere. But that doesn't make them right, necessarily."