The opening of Lem’s best-known novel, Solaris, illustrates his capacity, reminiscent of Arthur C. Clarke’s, to create believable accounts of futuristic technology, but the book’s central concerns are with the psychological and the theological rather than the technological.

The novel begins with a meticulous description of cosmic adventurer Kris Kelvin’s shuttle flight from the starship Prometheus to a research station on planet Solaris. The scientific verisimilitude of this introductory scene is followed by a mystical and claustrophobic tale of guilt and love by means of which Lem examines profound questions of identity, communication, creative thought, and divine power.

The central premise of the plot is that several generations of experimenters and theoreticians have attempted, without success, to comprehend and make contact with the godlike oceanic life form that surrounds the planet Solaris, an effort which is continuing. In the past, much of the research, which Lem describes by using his frequently employed device of elaborate digression, has involved cataloging complex architectonic structures on the planet’s surface and speculating on what thought processes might lie behind their appearance, evolution, and reabsorption. These speculations, a vehicle for conveying Lem’s own meditations on the nature of creative thought, vary from attributing nothing more than a mechanical origin to the structures to seeing them as something akin to the imaginings of Aristotle’s unmoved mover.

Most recently, a team of scientists has bombarded portions of the oceanic entity with high-energy X rays in the hope of eliciting a response. Ironically, the result is that the scientists themselves are experimented on by the intelligence they seek to understand. They exhibit the limits of their ability to comprehend and communicate with their own species. Gibarian, Snow, and Sartorius, the experimenters, have each been visited by neutrino replicas of people with whom they have had a past passionate entanglement, and each is driven to the brink of madness as he attempts to determine what his visitor is and how to behave toward it. By the time Kris Kelvin arrives and is haunted by his own companion, Gibarian has already killed himself and Snow and Sartorius are behaving bizarrely. Rheya, Kelvin’s visitor, is a nearly perfect replica of the beautiful young woman he had driven to suicide ten years earlier, and in relating to her, he must cope with the common science-fiction problem of how to treat an artificial human and the more original problem of how his past failed relationship with the replica’s model should affect his relationship with the replica. At first, he treats the new Rheya as a monster from whom he must escape, but gradually he accepts her individuality and refuses to abandon or destroy her despite the fact that he must remain on the planet to assure her continued existence. Although he sees her as a being separate from the woman he once wronged, by loving and protecting her he finds a way of expiating his past guilt, and she, in turn, frees him by accepting annihilation at the hands of the other scientists.

By the novel’s end, the planetary intelligence, which has put Kelvin in touch with his own humanity but at the cost of terrible torment to himself and others, remains as aloof from direct contact as always. His experiences on Solaris have suggested to Kelvin a paradigm for God, which solves the problem of the presence of evil in the world without attributing the creation of evil to God’s conscious choice. Perhaps God, like the oceanic entity, is “limited in his omniscience and power, fallible, incapable of foreseeing the consequences of his acts, and creating things that lead to horror.” Perhaps he is “sick” and driven by “ambitions” which “exceed his powers.” Here as elsewhere in Lem’s work, however, these suggestions are neither affirmed nor denied but simply left as tantalizing possibilities.

A film adaptation of the book was made in 1972 by Russian director Andrei Tarkovsky, and in 2002, Steven Soderbergh directed an epic Hollywood version starring George Clooney and Natasha McElhone.

Solaris, a planet which orbits a double star, is covered with an “ocean.” The ocean is a colloidal substance which, by altering its shape, somehow maintains the orbit of the planet, which otherwise would plunge eventually into one of its suns. Solaris was found by space travelers from Earth in the century previous to the setting of the novel. Its remarkable single inhabitant, the ocean, has caused an entire field of Solarian studies to arise and has produced an enormous library of scientific publications.

Kris Kelvin, a young researcher in “Solaristics,” arrives from Earth, descending from an orbiting rocket ship to a laboratory station which hovers above the Solarian ocean. He expects to join three researchers who have been there for some time. He finds the laboratory in great disorder and one of the scientists, Gibarian, dead from a recent suicide. Another, Sartorius, refuses to leave his room, and the third, Snow, reacts in terror to Kelvin’s arrival. He has to be convinced that Kelvin is who he claims to be.

Kelvin has an eerie feeling that he is being observed even when he is alone, and Solaris is thus, in part, a detective story, in which Kelvin, through a series of deductions, discovers what has caused the disruption in the work of the laboratory.

The Solarian ocean, in fact, is found to be a sentient being, capable of reading the human mind and creating, apparently out of its own substance, exact copies of persons from one’s erotic past. Gibarian has been driven to suicide by the presence of his “visitor,” a giant African woman whom Kelvin finds sleeping next to Gibarian’s corpse. Sartorius remains locked in his room, and Kelvin hears the wild laughter of a child through the locked door. Snow never permits Kelvin to see his visitor, who nevertheless always seems to be hovering nearby.

Kelvin’s first response to these apparitions is to assume that he has lost his mind, but when he checks what he has observed against the laboratory computer’s data he finds, somewhat to his dismay, that he is completely sane. At this point Rheya, Kelvin’s wife, who killed herself ten years before when he abandoned her, appears in his room—or so it seems. In fact, the visitor is not Rheya, though she obviously believes that she is. Kelvin’s response is to trick her into boarding a space shuttle, which he launches into orbit. This is only a temporary solution; a second “Rheya” appears. When she is shut in a room, she claws her way out because these “Phi-creatures” must constantly accompany their hosts. The wounds she suffers in this ordeal heal almost immediately, and when Kelvin tests her blood, he discovers that the ocean has created her body not out of atoms but from subatomic particles.

Kelvin has no illusion that this Rheya is the actual woman he once knew, but her devotion to him is so great that he is determined to save her, even though he suspects that the Phi-creatures cannot survive anywhere but on Solaris. Snow and Sartorius, however, develop a plan for destroying the visitors. Since they emanate from a human’s unconscious thoughts during sleep, they might disappear if an encephalogram of the person’s mind—his conscious thoughts—were beamed into the ocean. Kelvin agrees to let them use his encephalogram for this purpose.

Rheya listens to a tape in which Gibarian, before he died, explained his theories about the visitors. In despair, she attempts to kill herself by drinking liquid oxygen, but she recovers immediately. She and Kelvin both know that she is not Rheya, but Kelvin tells a lover’s lie: that she actually is human. He is determined to remain with her at the station for the rest of his life.

When Rheya asks Snow to confirm the truth of what Kelvin has told her and he does not, she convinces him to destroy her by means of the “destabilizer” which he and Sartorius have perfected. In his sorrow over the loss of Rheya, Kelvin asks Snow to join him in a recommendation to the four-power council on Earth for the total destruction of the ocean. Snow refuses; he still wants to achieve the great goal of human exploration of space—contact with an alien intelligence, a process understood in the novel as something resembling divine revelation.

Finally, Kelvin leaves the station to set foot on a kind of beach, a scrap of “land” created by the ocean, because he wants to make contact with the single creature of Solaris. When he holds out his hand to a wave, the “water” enfolds his hand but does not touch it. It is a despairing moment for Kelvin because he can see now that contact with the mind of the ocean is impossible and because he is sure that Rheya will not return. In spite of his disillusionment, he intends to stay on Solaris, hoping for nothing but persisting in “the faith that the time of cruel miracles was not past.”