Weston
Dr. Weston is the novel's main antagonist. His name is no accident: "Weston" acts as a symbolic representative of "Western" culture in all of its imperialist, capitalist, individualist glory. He does not act for his own material, individual interest, however; he represents that modern trend of utilitarianism in the world of academia and industry. By making Weston the novel's main villain, Lewis is making a statement about his own Western culture: it is a perversion of the ideals God has given to mankind as a result of the fall, prioritizing Man over all else. Weston's characterization further emphasizes this distinction: he is eloquent and composed when in his language and element, but when confronted with the goodness of Oyarsa and Malacandran language, he becomes a bumbling, comical figure who stubbornly holds on to his perversion in the face of redemption.
Devine
Devine's symbolism is perhaps a bit more obvious and less grandiose than that of Weston. He also represents a certain aspect of Western culture: materialistic greed. Even his name reflects this: "dives, divitis" is a Latin adjective meaning "rich." His only motivation in making the voyage to Malacandra is to acquire precious materials that will make him rich on Earth. His discourse with Ransom reveals that he views all other ways of life with a lens of harsh cynicism and flippant sarcasm, valuing only money above all things. His motivation is far more selfish than that of Weston, but even more perverted.
Ransom
Ransom himself is a symbol representing the substitutionary atonement of Christ - he is the novel's "Christ-figure." By stumbling upon Weston's experiment, he saves the life of the innocent Harry, unwittingly offering himself as a sacrifice in Harry's stead. By being offered to the sorns (to appease their appetites, as Weston believes), who in turn report to Oyarsa, Ransom has effectively become a sacrifice to God, paralleling Jesus's sacrifice to appease God's wrath on humans. His symbolism continues in the later novels of the series as well.
The Silent Planet
The Silent Planet is a symbol used by the Malacandrans and their Oyarsa to refer to Earth, which has been corrupted by evil forces and "bent" away from the true and good path. It is silent because it does not live in community with the other planets, who delight in holy communion with each other and with the Old One (and his son, Maleldil the Younger). Its silence reflects its fallenness; Ransom's task is to bring light to this darkened world.
The Sun
The Sun comes to represent the power and omnipresence of divine goodness. When Ransom first enters space, he marvels at the contrast to what he imagined: it is not cold and dark, but warm and bright. Weston sardonically asks if he's forgotten about the Sun. The Sun's warmth and light extend throughout the entire galaxy, showing the magnitude and greatness of the Old One's (God's) love and power.
