Perelandra is a novel about Life. It is inherent in the plot, the characters, and even the landscape of the Perelandran world. Perelandra is a young planet, and its sole rational inhabitants had not yet been tempted by sin. Maleldil sends Ransom in order to act as a counterforce to the efforts of the Tempter, who is going to try to seduce Tinidril and convince her to sin against Maleldil. "The wages of sin is death" (Romans 6:23), so preventing sin is, in effect, preserving life on Perelandra. Ransom's mission is therefore a life-saving one, working to maintain it against the forces of Death.
The planet of Perelandra is a beautiful and life-infused one. Being the equivalent to the pre-Fall Garden of Eden, it is perfectly free from sin and death. All its inhabitants live in peaceful harmony in worship of Maleldil, free from anxiety. An interesting parallel: the sin of Adam and Eve in the Garden of Eden that led to the Fall of Man was the consumption of a fruit from the tree of Knowledge of Good and Evil. In Perelandra, Tinidril (the Eve-figure) seems to have no concept of good or evil as such, implying that this is the ideal, pre-Fall state of humanity. When Ransom arrives, saying that he comes in peace, she asks, "What is peace?" Having no concept of brokenness, she does not understand the concept of goodness as the opposite. Living in perpetual peace, she does not know an alternative, and therefore the word "peace" means nothing to her.
The preservation of this innocence is Ransom's mission in the novel. He works against the efforts of Satan (the "black archon") in the form of Weston by debating and, when that fails, physically attacking him to prevent his victory. By defeating the power of Death, Ransom succeeds in his mission, ensuring that the Fall of Man on Venus will never occur. There is an intriguing side effect to this positive development: man will never fall from grace, so there will be no need for Maleldil to sacrifice himself as a substitution for the sins of humanity. This act of loving sacrifice is the act by which God most glorifies himself, and it is no longer possible to enact on Perelandra. However, as Ransom points out, God works all things out for good, and even the lack of evil cannot stop the abundance of his goodness.
There is another interesting parallel between Ransom and Maleldil (Jesus). Ransom's mission is to travel to a world in which he is an alien in order to preserve the innocence and purity of its inhabitants. Jesus did the same thing: he came to Earth, a place in which he was an alien, and provided a way for its inhabitants to preserve their lives and enter into harmony with God. Even some of the smaller points indicate this symbolism: Jesus had to descend into the grave (Hell) for three days following his crucifixion (the act by which he took the punishment for man's sin). Similarly, after attacking and wounding Weston, Ransom descends into the dark and occasionally fiery subterranean caves on Perelandra, where he does battle with Weston, who represents the powers of darkness. He ultimately triumphs and reascends to the surface, paralleling Jesus's resurrection. In the battle, though, he becomes wounded in his heel. This image is a Biblical one, an allegory for Jesus's experience of Death (corresponding to Ransom's descent) from Genesis 3:15: "He will crush your head, and you will bruise His heel."
