4 ideas
On Rakhat, the human mission plants a vegetable garden and teaches the Runa villagers of Kashan to grow their own food, meaning it as simple kindness. The Runa are a herbivorous species whose numbers are strictly controlled by their Jana'ata rulers. A food surplus lets the Runa raise unlicensed children, so the Jana'ata answer with a punitive massacre of the village, and the mission's members are killed or captured.
Rakhat has two sentient species: the Jana'ata are carnivores who eat the Runa, and the Runa are herbivores who serve them. The Jana'ata keep this order stable by licensing who may breed on both sides and by culling the Runa. Most Runa experience the system as normal rather than as oppression. The book uses this to show a social order that looks monstrous from outside but has an internal logic that outsiders cannot see until they break it.
Sandoz came to believe every coincidence that brought the mission to Rakhat was God's hand. That belief means his later mutilation and repeated rape cannot be dismissed as random. They seem to be part of the same divine plan, so either God willed them or there was never a plan. The stronger the conviction of being led, the more complete the spiritual collapse when the outcome is horror, and the novel's title presses this point: the sparrow still falls.
Sandoz returns to Earth accused of prostitution and of killing a child. He refuses to explain, and the Jesuit inquiry and the public treat his silence as an admission. That truth is exactly what shame keeps him from saying. Institutions fill a victim's silence with the most damning available story, and the testimony needed to correct it is the testimony that costs the victim the most to give.