After Sophon, Cheng Xin, and Luo Ji's conversation becomes public, humanity turns almost collectively to the problem of creating a cosmic safety notice. Proposals arrive from every level of society, but the more people study the issue, the more the idea becomes a seemingly unsolvable riddle.

The proposals divide mainly into two camps. The declaratory camp wants to broadcast a message proclaiming Earth's harmlessness, but this approach fails because no unknown civilization in the dark forest would have reason to trust mere words. The self-mutilation camp argues that Earth must become genuinely harmless, proposing technological regression, the abandonment of the space and information ages, or even deliberate reductions in human intelligence.

Other schemes become more extreme, including self-deterrence systems that would automatically destroy humanity if humans acted inconsistently with their harmless claims. These ideas reveal both desperation and imagination, but they still miss the essential problem: a dark forest strike is casual, distant, and based on minimal observation.

Because most civilizations would see the Sun only as a distant point of light, any safety notice must be trusted without close inspection. Human acts of regression, sacrifice, or control would be like performance art with no audience. A real cosmic safety notice would have to make a remote observer instantly conclude that the star itself posed no threat, which appears impossible.

The excerpt ends by questioning why Sophon refuses to reveal the method for sending such a notice. Although the Trisolarans have reason to withhold technology and fear future human revenge, a genuine safety notice would also make Earth harmless to them, so Sophon's silence remains unexplained.