It is one thing to do a television biography of a historical

figure; it is quite another to do one about a living person. The historical figure is mythicized; the living person may be, too, but there are boundaries. Current

images, common knowledge, popular consensus shape them. ''Pope John Paul II,'' with Albert Finney in the title role, is at once enhanced and hindered by this. In real life, the Pope's story is so good that it is sure-fire for a biography. And in real life, we carry around our own picture of the Pope. A filmmaker can tamper with this only lightly, not only because heavy tampering would be distasteful, even irreverent, but because it would be jarring, an assault on our sensibilities. ''Pope John Paul II,'' therefore, stays with the facts, or the facts as we know them. Mr. Finney walks through history in a three-hour movie that is almost a series of anecdotes. It will be shown on CBS at 8 o'clock tonight.

The vehicle for the movie, which has an original script by Christopher Knopf, is the flashback. Thus, it is Sept. 29, 1978, and Pope John Paul I has died in Rome after a reign of only 33 days. Mr. Finney, as Karol Cardinal Wojtyla, hears the news in Cracow, Poland. He stares out the window and sees some boys playing soccer. An instant later, it is Wadowice, Poland, 1938. Karol Wojtyla, 18 years old, is playing soccer. He is an upright, open youth, serious, though not solemn, religious, but not pietistic. The persona matches the one we think the Pope probably had at 18. Michael Crompton, the British actor who plays him from 18 to 26, even looks the way we think he looked. There is nothing jarring.

Around young Wojtyla, meanwhile, there is the swirl of great catastrophes. While he and his father say the rosary together in the kitchen of their modest apartment, they hear the sound of marching feet. It is the Germans, come to occupy Poland. Immediately, we see Archbishop Adam Sapieha (Jonathan Newth) facing the Nazi Governor General. ''Poles, like Jews, are untermenschen - subhuman,'' the German says. ''They have no right to life. The task of the priests is to keep the Poles quiet, stupid and dumb witted.'' Obviously, you cannot show the life of the Pope without showing his times. It is certain that they shaped him. But the problem is that the film sometimes seems to be telling two stories: one about the Pope, the other about the times. Sometimes, when the two join, there is confusion. Young Wojtyla is at an underground religious meeting of some kind. There is an argument. A youth hands over a pistol. Presumably, this has something to do with how one fights oppression - with faith or guns - but this viewer wasn't sure. The incident, one suspects, is based on something that really happened, and the filmmakers, striving for fidelity, declined to take liberties. One wishes, however, that they had. We get the outline of the Pope's life, but we seem to be missing the essence. Or, we are in Cracow. It is 1940. Young Wojtyla, the victim of an accident, awakens in a hospital bed. ''It's what I want to do - the answer,'' he tells his father. ''It's what I want to do with my life.'' He means that he will become a priest, but we have to guess at that. The scene has no antecedent. Credit the script writer, Mr. Knopf, the director, Herbert Wise, and the tasteful producers, Alvin Cooperman and Judith DePaul, for not inventing the Pope's interior life; yet, at the same time recognize the problem: It is the interior life that presumably separates the Pope from the rest of us. We would like to know something about it.

The problem is compounded when Mr. Crompton leaves the film, at about the half-way mark, and Mr. Finney takes over entirely. (Father Wojtyla, newly ordained, goes to Rome. When he returns three years later, he is Albert Finney.) Mr. Finney is a fine actor, but he is not playing a man so much as he is portraying a monument. He takes children for a hike; he argues with the Communists; he is told he will be a bishop. The film is dealing then with the more publicized parts of the Pope's life, and so there is even less room for invention than before. Historical incident leads to historical incident. Mr. Finney, in a way, is bound and gagged. He has no room to maneuver.

Some incidents, meanwhile, just seem to be there because they are there. In Rome, Bishop Wojtyla forgets the red socks he must wear for a ceremony. He wears black socks, instead. In the film this is meant to show us he is a regular guy; presumably, this episode is based on a real incident. But unless you're paying close attention, you'll miss the significance of the ceremony: Bishop Wojtyla is being made a cardinal. Or, on skis in the Tatra Mountains four years later, he is stopped by border guards. Apparently, he inadvertently strayed into Czechoslovakia. The guard captain is respectful. The Cardinal skis away. The point seems to be that the Communists now realize he is someone to be reckoned with, but once again we have to guess.

All this is unfortunate because ''Pope John Paul II'' has some nice things going for it. For one, there is the cast. Mr. Finney may not have much to do besides pose, but a number of interesting actors tumble in and out, even if briefly. Among them are Robert Austin as the Nazi Governor General, Alfred Burke as the Pope's father, John McEnery as a monsignor and Nigel Hawthorne as Stefan Cardinal Wyszynski.

In real life, Cardinal Wyszynski appeared to do a good deal of campaigning to have his friend and colleague Karol Wojtyla elected Pope. The movie makes a few references to Vatican politics - arguments between conservatives and moderates, for instance - but otherwise the election seems to have been ordained only by God. It is even possible that the Pope did a little discreet campaigning himself in the years before he was elected. He left Poland, traveled about and met other cardinals.

Certainly, Karol Wojtyla was ready to become Pope. Most Vatican observers agree that he moved into the papacy without hesitation, becoming in the process one of the most remarkable, and interesting, figures of our time. The movie is respectful. It doesn't jar our picture of the man, but it doesn't add much to our insight, either. You may wish it had taken a few risks.

photo of Albert Finney