Fashion in the communist world is on course for potentially dramatic change. Ideologues and their dowdy Marxist hemlines are going out. Pragmatists - even if not always radical reformers - are moving in. Hungary has taken a lead. Its party conference last month wrote finis to a book of old-fashioned ideological writ and then installed a more open-minded, younger, impatient, and ``with it'' leadership.
The Soviet Union perhaps will catch up later this month by adopting Mikhail Gorbachev's effort to replace traditional party fashion-setting with major limitations on its authority and power.
In a quite startling way, the recent superpower summit in Moscow provided a still wider background for the changes at work under communism and the new modes of ideological thinking that are appearing in the world at large.
On one side, some of the ``dragons'' - to use Mr. Reagan's word - of demod'e anti-Sovietism were slain. On the other, there was further evidence of Mr. Gorbachev's resolve to free serious business from the stereotyped anti-American attitudes of the Cold War.
Reagan told Soviet students they are living in exciting times. The same might be said of their counterparts in eastern Europe, where generational trends and movement - that a decade ago seemed as distant as many of the latest developments in the Soviet Union - are now in progress
In Moscow of all places, a ``democratic union'' openly demonstrated, unmolested, right after the summit. Church dignitaries from around the world gathered on a first-ever permitted scale for celebration of Russia's Christian millennium.
In Hungary, democratic forums, youth unions, a ``network of free initiatives,'' and embryo labor unions tumble over each other to be born. They operate within existing law as they wait for pending legislation on a ``right of association'' outside the strict Communist Party mandate. In Poland, something similar is afoot, though thus far with more official uncertainty and less tolerance.
These new forms transcend much of the old established mode of East European dissent. With the years it has tended to become standardized, a gallant part of the scene but predictably little heeded by the man in the street, who is concerned primarily with personal problems.
Gorbachev's glasnost (openness) now is striking a notably greater response among the younger, more sophisticated generation than the old pattern of lengthy cyclostyled declarations and underground sheets that proliferated on almost every subject under the sun.
The Hungarian conference was glasnost at its best. Only this could explain the unceremonious clean out of the old guard - prestigious leader for 32 years, Janos Kadar, among them.
As he left, Mr. Kadar took with him a whole portfolio of traditional ``party line'' which glossed over failure with fanciful premises of prosperity ahead.
His successors promise an altogether new look.
Top of the list - as on Gorbachev's - are curbs on the ubiquitous party control of society, a freer functioning government, a tremendous enlargement of opportunity for economic initiative, above all in major enterprise management, and, concommitantly, in opening up the private sector under genuine incentive conditions.
On paper, of course, it all sounds fine. But only the practice will show how far the promised reforms will reach the proclaimed goals of market economics and political pluralism, particularly the latter.
It is not a simple problem of outright opposition as in Czechoslovakia, or Romania whose archly-autocratic leader says the need for reform ``simply does not exist.''
Uncertainty relates more to doubts - even among some reformers - who still fear the new democratic forums as threats to the party's ``leading role'' which they believe is essential.
Open elections, yes. Constitutional reform to ``separate'' party and state also - even a second parliamentary chamber, ``a sort of senate,'' as one hears here. But the party is not yet ready to relinquish the finally decisive role. Open pluralism of interests does not apparently mean pluralism in parties.
For all the changes, the cul-de-sac remains and will do so until a communist party comes along which is realistic enough to admit that, if reform is really to mean what it says, the single party state itself must be modified.
One of the unequivocal reformers now brought into the Hungarian leadership put it this way. ``Let's get the market economy right first,'' he said. ``Then we can begin to think about party pluralism.''
For him, the essential first step is for a more ``legal'' society firmly rooted in law and individual rights. With this accomplished, he adds, ``We can take on the question of institutionalized interest groups. It needs time. But these in due course could assume a normal opposition or alternative ideas role within a `socialist constitution' just as British or American parties operate under a monarchy or a republic.''
Perhaps he has a point. Only time will show.