MARK RUDD'S sentences don't play back very well on the instant replay. He doesn't prepare what he is going to say in his speeches, and his mind seems to be listening to his own voice, forming its next ideas on the basis of what it hears. And he falls back on using a dogmatic-sounding language of generalization ("imperialism," "corporate expansion," "co-optation") that assume the listener already largely understands the things he is talking about.

But Rudd is not the spokesman of the Columbia revolt or its ideologue. He is the leader (like field commander) of the Columbia students who do already understand the issues Rudd generalizes about. And these intricate issues, such as the interests of Columbia's high-level decisionmakers, are easier to talk about when reduced into less painfully complex phrases.

So Rudd has an excuse for talking the way he does. But trying to figure out his ideas is still confusing. He contradicts himself, sometimes within the same sentence. In a discussion after the SDS film Friday night he told a group of people, "The Left is completely bankrupt; but the potential is there."

Rudd wants, let's call it, a revolution. His activities--stopping registration, holding buildings as ransom for six demands--have been an attempt to influence decisions students normally couldn't change and building strength for an even greater power in decisions. But how what the revolutionaries are doing at Columbia ties into what they hope is a world revolution Rudd can't tell us.

"We have no revolutionary program," he said. "We know we don't have any revolutionary program. We don't know what the agent for the revolutionary program is going to be. It's certainly not going to be the students, who have the power to work for change through the existing structure."

To find meaning and order in what happens to students and how they react to what happens to them, Rudd drags in too many irrelevant historical events. He insisted Friday that the situation at Columbia was "directly analogous" to the long chronology of the German student movement that his audience listened to just before they heard him. Perhaps because the difficult struggle of revolution unites those of similar causes, Rudd feels sympathetic to the Germans. But to lump together two such different and complex situations as the same is one of the dogmas of the old academics that new thinkers of the New Left are supposed to be trying to escape.

Rudd said that his ideas were always changing, and explained that right now they included Leninism and came out of what happened in France last May. Again one can question his application of ideas first from a country where the desperately poor were over ninety percent of the population, and second from a country where students and workers had a historic alliance.

Later Rudd was asked if the Columbia movement wasn't nihilistic. No, he answered; their struggle was based on a clearcut Marxian dialectic. One had, on one hand, the Columbia ruling structure, he explained. Complete opposition to this would give rise to the exact opposite, which was, he said, a national democratic socialism. Just why national democratic socialism has to be the exact opposite of the Columbia ruling structure isn't at all clear to me. And it seems to me that Rudd decided it was so because it would best fit his argument.

SOMETIMES Rudd says so little about what he's talking about it's incomprehensible. this can be irritating and insulting: "Being for McCarthy is not being for a democratic community; it's a barrier of ideology. That's what Deitrich (the German speaker) and I faced tonight. It's what we've got to break through."

Or the incomprehensibility can be just amusing: "These people would always stand on the side of the status quo. And that's the one main lesson of Columbia. And that lesson was pretty much embodied in our slogan, which was 'up against the wall, motherfucker." The slogan very clearly defined the enemy. It says you're there; and we're here." What the slogan really means is "we've got power, too." Rudd has a lot of ideas; but they are all jumbled. `

But let us remember that Rudd isn't a speechmaker, and that what is easy to pick apart with careful semantics on the clear white page of the newspaper sounds a lot better when Rudd says it into a bullhorn under the towering buildings that make up Columbia's campus. Rudd is a revolutionary leader, and a pretty good one. Using the kind of movement jargon that keeps the revolutionaries at home with each other (such as calling everyone "brother") and by taking a tough stand against all "undemocratic" institutions at Columbia, he has held the Left together.

The Columbia Left, then, initiates the action. If they take over a building, they then see if the liberals will decide to follow. If they don't get enough general support, the Left gives a little; but this way they don't have to spend a lot of time voting and deciding in the beginning.

Mark Rudd is an example of what future student leaders at other campuses might be like. Power, the role of leader, fell to him arbitrarily. He was the head of SDS at Columbia in the spring of '68 as he was trying to do. what other heads of SDS had always been trying to do. Then the sit-ins worked just right; and the press made him a national figure. Rudd, himself, insists that he is no more the leader of the revolt than half a dozen other people.

Leading the Left requires a new talent. The people on the Left have usually worked out the complexities of the issues in their own minds; they need to be stirred to action. So Rudd's self-contradictions often are buried in his complex grammar as he jabs his listeners' moral emotions.

And, too, Rudd is always being asked to explain things and is badgered by the press to vocal exhaustion. However, one can't help but feel that his tendency to let the urgency of political endeavor get in the way of a careful choice of his words is a little scary.