In Andrei Tarkovsky’s Stalker, it’s said that the mysterious Zone that the protagonists explore is in a constant state of change. Tarkovsky’s cinematic universe is in the same condition. Film, for him, is a way of imprinting change. He is concerned with processes: fire, water flowing, the sun rising behind a farmhouse (in an incredible shot in Nostalghia), microcosms that are decaying but not dead (since matter is constantly being stirred by breezes or by the impulses that cause water to flow, and since out of the decay, life will come).

That Tarkovsky’s films themselves constitute an organic whole is apparent, and this will be confirmed by the MFA’s retrospective of all seven and one half of them. (The half is the medium-length The Steamroller and the Violin, the director’s 1960 diploma film, which will show on March 6 at 6 p.m. and March 15 at 11 a.m.) It’s pointless to warn viewers about the alleged slowness of these works, or about their refusal to make any concessions whatever to the supposed requirement that a movie should entertain. Tarkovsky’s films are foremost among films that make their own way of dwelling within time a primary preoccupation; they demand a level of attention far beyond that needed for the task of being entertained by commercial cinema, and they repay this attention with their complexity, precision, and depth.

Ivan’s Childhood (1962; March 14 at 6 p.m. and March 16 at 1 p.m.), Tarkovsky’s first feature, provides an access to things and sounds that seems unmediated: watching the film is like sharing in a dream being dreamed by the material world itself. Some of the plainest, most concrete images in the film — shots of animals, for instance — occur in dream sequences, whereas the sequence in which history enters the film most forcefully — the sequence of the war’s end — is filmed as if it were a dream.

In Tarkovsky’s later works, dream and reality fuse. Both Solaris (1972; February 27 at 7:10 p.m., February 28 at 7:10 p.m., and March 1 at 3 p.m.) and Nostalghia (1983; March 7 at 7:20 p.m.) end with objective hallucinations in which the heroes’ memories find concrete realization. The whole of Mirror (1974; March 14 at 8 p.m. and March 16 at 3 p.m.) is an extended act of remembering, the building of a personal myth with several levels (each Tarkovsky film is like a house or a landscape that’s familiar but different each time you visit it), in which remembered experiences, recounted incidents, dreams, poems (those of the filmmaker’s father, Arseniy Tarkovsky), and historical events reflect one another.

Mirror is the farthest Tarkovsky went in dissolving narrative. The war film Ivan, like the mediæval panorama Andrei Rublev (1966; March 8 at 10:30 a.m., March 9 at 2 p.m.), is structured in extended episodes that tell a linear story obliquely (since the episodes are at varying distances from the main story). In Solaris, key narrative events are elided; the movement of the film is keyed to changes in consciousness, perception, and atmosphere. Stalker (1979; March 13 at 7:15 p.m. and March 15 at 2:20 p.m.), with its simple journey structure, is a largely " linear " film, but one in which whatever belongs to narrative is beside the point. Here and in Nostalghia, storytelling is submerged in a wealth of detail, the data of consciousness: movements, waiting, recollections.

All Tarkovsky’s films are nostalgic: they view the world as in danger of being lost, and they see it from the point of view of someone striving to hold onto it. The heightened awareness of aural and visual detail in his work needs to be seen in relation to this emotional imperative. The melancholy opening of Solaris is characteristic: the hero wanders alone by the lake near his father’s house, taking leave of Earth, perhaps for the last time, before his trip to the planet Solaris. The optimism of the film lies in the affirmation that Earth can always be, and is always being, created by the human spirit: the struggle to remain human (or, in the case of the simulacrum Harey, to become human) gives value to existence under the most hostile conditions.

In Stalker, Tarkovsky returns to the theme of Solaris, this time abandoning the science-fiction trappings in which he seems to have been only mildly interested and that he regarded as a distraction from the essence of the story. He delegates to the dialogue the full responsibility of conveying the science-fiction premise; he leaves the decor (which he designed himself) free to represent a world that’s scarcely a stylization of late-1970s Soviet reality (the film was shot on location in the Estonian capital of Tallinn and in the Mosfilm studio in Moscow). The world of Stalker is fully real and present, and though the time of the narrative is shifted, we know, into the future (since no such disaster as that which has created " the Zone " has yet happened), the shift required to believe in the film’s world is a lateral rather than a forward one, since the disaster has already happened in potential and needs no particular actualizations to become real (not that these are lacking: Nagasaki 1945, Hiroshima 1945, Chornobyl 1986 — this last seven years after the release of Stalker, and eight months before Tarkovsky’s death).

The imaginative sidestep of Stalker is the same move made in Tarkovsky’s other films, which are about life lived alongside history, its effort and endurance, the creating and reviving of purely personal meanings, the formation and disintegration of families and small communities. The re-creation of mediæval life in the vast fresco of Andrei Rublev is a great achievement, the more so since it’s linked so thoroughly to a personal adventure that is also the journey of the human spirit: only through the hero’s experience of earthly suffering, fear, and hope can his art have meaning. Even more moving is Tarkovsky’s rendering of 20th-century history in Mirror, with its affirmation of memory as a vital principle and its sense of the machinery of history at work beyond the sphere of the film’s characters, who try to avoid getting squashed by it (a point made in the tremendous sequence in the printing shop, which evokes the daily experience of the Stalin era).

The central problem of Stalker is the central problem of all Tarkovsky’s films, but stated explicitly for the first time: the possibility of a single person’s taking responsibility for all humanity. Stalker postpones a decision on this question. In his next two films (which were also his last two), Tarkovsky answers it in the affirmative. In Nostalghia, the passage of a man carrying a lit candle across a drained pool is supposed to save and give meaning to the world. In The Sacrifice (1986; March 8 at 2:15 p.m.), nuclear war is miraculously avoided by one man’s private decision, before God, to give up everything he has and fall silent.

The Sacrifice is a film toward which I feel ambivalent. It’s a highly personal work that must occupy a key place among Tarkovsky’s films for anyone interested in them as spiritual autobiography, but it seems to me almost suffocating in its perfection and troubling both in its endorsement of the paternalism of the hero’s sacrifice and in its portrayal of women as hysterical or childlike (a tendency already obvious in Rublev, Solaris, and Nostalghia). Yet it has two of Tarkovsky’s greatest shots: the magnificent long take at the beginning of the film, and the long take of the burning house near the end.

Such shots are representative of the filmmaker’s insistence on extending the image in all directions: up (as at the beginning of Ivan’s Childhood and the end of The Sacrifice), sideways, down. Camera movements gradually unfold spaces, revealing unexpected distances (Andrei Rublev). In Mirror, the main movement is inward, toward the past, and it’s complemented by a movement back and out (emphasized by the winds that repeatedly come out of the landscape, toward the camera); in Nostalghia and, especially, The Sacrifice, sweeping lateral tracking shots emphasize the horizontality of spaces that resemble stages, suggesting a need to dramatize inner states.

Tarkovsky’s camera is intent on testing the reality of the people and the things it photographs, a reality that for him is confirmed by imperfections, dirt, signs of age and decay (in Solaris, all the characters have scars; the universe of Stalker is one of gorgeous wreckage, decomposition, flooded interiors). Mirror and Stalker are films of astonishing density: the eye is encouraged to go deeper into the multi-layered images, which give the impression that the detail they contain is inexhaustible. Video or DVD can at best only suggest this impression: only the experience of seeing Tarkovsky’s films in screen projection, in good prints, can make it clear why he is among the great explorers of cinema.