For many of us, the difficulty in grasping what Mikhail Gorbachev is up to is in fitting the notion of reform to our belief that Soviet society is organized by a Marxist-Leninist party precisely to contain reform. It is not simply that it's hard to understand why the single ruling party would want to loosen its grip. It's hard to understand how that can even happen under a communist system. We know it can't.

But how do we know? It's not enough to say that we consult our suspicions or our hopes, as the case may be. That gives us a political judgment -- conservatives have suspicions about Kremlin change, liberals have hopes -- but hardly the last word. If we turn from peering into the Soviet future to peering into the Soviet past, then we arrive at an even more clouded place. For students of the Soviet past are torn.

A British student, Aileen Kelly of Cambridge University, writing in the Sept. 24 New York Review of Books, observes of the two principal contending schools that recent events have increased the distance between them, ''as each attempts to influence Western reactions to Gorbachev's reforms."

A ''totalitarianism'' school, including (more or less) Richard Pipes, Adam Ulam and Zbigniew Brzezinksi, sees the reforms as cosmetic and tactical, and warns the West not to lower its guard. This school, Kelly suggests, leans on the late British scholar Leonard Schapiro's premise ''that Stalinism was the logical successor to Leninism, and that the dynamics of Soviet history since 1917 can be explained by one determining factor: the ruling party's commitment to total power.'' Believing the Soviet system to be unique, this school tends to ascribe its sole paternity and all its evils to the Russian revolutionary tradition.

A ''revisionist'' school, including Stephen Cohen (who named the schools) and Jerry Hough, takes the reforms seriously and urges the West to respond positively to this rare opening. This school finds that the party, rather than being a frozen monolith, now offers a genuine competition of factions and interest groups within the elite. The revisionists believe that the Soviet system, like other systems, is a complex product of many historical strands.

So says Aileen Kelly, reviewing a posthumous collection of Leonard Schapiro's writings, ''Russian Studies.'' She goes on to make a learned critique of the Schapiro contribution, and I go off on a little personal detour.

As a graduate student in Russian history in the 1950s, I read Schapiro and accepted him as a giant in the field. He and his like taught us everything we knew about the communist party -- knew then, anyway. Certainly what he taught seemed completely consistent with what was going on -- the Hungarian revolution, the admissions of Stalin's terror -- in the real world. Unquestionably his influence in the realm beyond scholarship was immense.

Now, 30 years later, comes Aileen Kelly to tell us in a respectful but unmistakable way that what we learned was not the revealed truth but merely the ''dominant orthodoxy in Soviet studies'' of the day.

I forgive Aileen Kelly, who is probably still in her teens. I am even prepared to acknowledge she has a point. New experiences and expectations can contribute to generational variations in writing and reading history. All of us know people who failed to replenish intellectual capital. In any event, the two schools in Soviet studies have been going at it hot and heavy for the last few years, and I want to believe improved understanding will result.

It would be an awful thing, however, if one ''dominant orthodoxy'' were to be replaced by another. Already in historical circles, and in political and journalistic circles, there is a striking readiness to accept as accomplished fact schemes that are no more than a glint in Gorbachev's eye. The Bork controversy has sensitized all of us to the phenomenon of ''result-oriented'' jurisprudence. We do not need result-oriented scholarship.

The great argument about the Soviet Union has always been whether it is a state among states, with its own tradition and style but ultimately motivated by the same aims as other nations, or is one of a kind, bound by no rules other than its own. I think it best to regard the question as still open -- open and urgent