West Berlin — Baron Richard von Weizsacker comes from one of those aristocratic families in which public service is taken for granted. It is not surprising that he is a former vice president of the Bundestag, a former lay moderator of the Protestant Church Assembly, the present mayor of West Berlin, and the future president of West Germany.
What is surprising is the way he has blossomed in the past 2 1/2 years in his chosen service of politics. He is, after all, somewhat reserved, a patrician from head to toe.
He is noted for not trimming conscience to politics: He was one of only four conservative members of Parliament to vote for Social Democratic Chancellor Willy Brandt's detente with the East back in the early 1970s. And when the Christian Democrats sent him to the Social Democratic stronghold of West Berlin at the end of the '70s, he came as a man with no practical experience in the rough-and-tumble of municipal politics.
Yet von Weizsacker won City Hall away from the demoralized Social Democrats in the next election. And in his years in office he has come to personify conciliation of clashing viewpoints in this often difficult city.
And in a West Germany that is entering a period of polarization, it is precisely this talent that will be called on when he becomes federal president - unopposed by the Social Democrats - next spring. He himself sees the presidency as something of an extension of his task in West Berlin - ''to combine tolerance among all those diverging views on the one side and yet keep people together in the feeling of being Berliners'' - or Germans.
Berlin has ''so many divergent groups, people, initiatives, aims,'' explaines von Weizsacker in an interview. ''Not to let them just fall apart and just fight one another, but rather to keep them together with all their conflicts, is the main task of a metropolitan area. A generation conflict usually is decided in such a metropolitan area.''
Now, von Weizsacker continues, ''We are heading for growing tension, separations, for a lack of orientation'' in West Germany as a whole as young people express their dissatisfaction with the answers of their elders ''as to the safeguarding of a decent life in their future.''
Many young people, von Weizsacker goes on, referring especially to the current missile debate, ''do not trust our ability to ethically command what we can do technologically.'' And he adds, ''they have of course the credit of having alerted the older people in various fields (such as) environmental questions and the relationship between material and nonmaterial aims.''
As head of state, von Weizsacker hopes to meet this ''growing uneasiness, uncertainty, lack of orientation'' not by ignoring or riding roughshod over it. Rather, he honors young people's questioniong, if not necessarily agreeing with their specific answers.
It is not always completely clear to outsiders just how von Weizsacker's conciliation works, but obviously it has worked in West Berlin.
He has kept together the cantankerous conservative and liberal wings of his own party for a start - a not inconsiderable feat in this city. He has calmed down the squatters (and their violent fringe) by a combination of slow negotiation of rental contracts, some controversial evictions, and a healthy housing construction program. Through it all, von Weizsacker has won the affection of West Berlin's large middle class and its many pensioners - and even the grudging respect of the city's lively countercultural ''scene.'' He is no butt of intellectual's jokes, as some of his conservative colleagues are.
Die Zeit's West Berlin correspondent concluded that von Weizsacker has brought ''serenity, magnanimity, and breadth of thought'' to his job - and is probably the second-best mayor West Berlin ever had, after the great postwar Ernst Reuter.
Von Weizsacker will have ample occasion to draw on these qualities after assuming the West German presidency next spring. The post is above politics. It is intended to represent and unify the broad spectrum of West Germans.