Earlier, aboard Judgment Day, Mike Evans conducts his twenty-second real-time exchange with Trisolaris through a sophon display. The Trisolarans explain that they cannot understand part of humanity’s cultural materials because, in their experience, “think” and “say” are effectively the same act: their brains openly emit thoughts, so they have no private inner speech and no separate organs of communication.

Trying to locate the gap between the two species, Evans tells a simple story about a wolf deceiving children by pretending to be their grandmother. The Trisolaran response reveals the central difference: because their thoughts are always exposed, they cannot grasp lying, cheating, scheming, or pretending. Once Evans realizes that Trisolarans live in total mental transparency, he understands why they struggle with human behavior; after a pause, the Trisolaran speaker reaches the same conclusion and ends the conversation with a decisive shift in attitude: “I am afraid of you.” This is Evans’s last message from Trisolaris.

At dusk at Yang Dong’s grave, a brown ant crawls over the gravestone while Luo Ji arrives with flowers and then meets Ye Wenjie. Luo Ji had known Yang Dong in high school and now teaches sociology rather than astronomy. Ye, walking there regularly after her daughter’s death, uses their chance meeting to steer Luo Ji toward a new field she names “cosmic sociology,” arguing that a universe filled with many civilizations can be studied more cleanly than ordinary human society.

Ye explains that cosmic sociology should begin from two axioms: survival is every civilization’s primary need, and civilizations continuously grow while the total matter of the universe remains constant. She adds that two further concepts are necessary to build the theory: chains of suspicion and technological explosion. Ye refuses to elaborate, insists Luo Ji is clever enough to work them out, and hints that she will not be available for future guidance, saying she has now fulfilled her duty before departing into the twilight.

After Ye leaves, Luo Ji remains silently at the grave for a time and then goes. The ant and a spider continue their instinctive routines, unaware that they have witnessed a pivotal moment: the formulation of the basic principles of cosmic civilization. The chapter frames immense historical consequences through tiny, indifferent observers, contrasting instinctive life with the dangerous new understanding taking shape between humans and Trisolarans.