Fermi paradox
The Fermi paradox, or Fermi's paradox, named after physicist Enrico Fermi, is the apparent contradiction between the lack of evidence and high probability estimates for the existence of extraterrestrial civilizations. The basic points of the argument, made by physicists Enrico Fermi (1901–1954) and Michael H. Hart (born 1932), are:
According to this line of reasoning, the Earth should have already been visited by extraterrestrial aliens. In an informal conversation, Fermi noted no convincing evidence of this, leading him to ask, "Where is everybody?" There have been many attempts to explain the Fermi paradox, primarily either suggesting that intelligent extraterrestrial life is extremely rare or proposing reasons that such civilizations have not contacted or visited Earth.
The Fermi paradox is a conflict between the argument that scale and probability seem to favor intelligent life being common in the universe, and a total lack of evidence of intelligent life having ever arisen anywhere other than on the Earth.
The Dark Forest
Back on Earth, Luo Ji and another contemporary, Da Shi, discover that star 187J3X1 has been destroyed, causing the UN to restore Luo Ji's Wallfacer status. Luo Ji explains to Da Shi the implications he derived from Ye Wenjie's two axioms of cosmic civilization: 1. Each civilization's goal is survival, and 2. Resources are finite. Like hunters in a "dark forest", a civilization can never be certain of an alien civilization's true intentions. The extreme distance between stars creates an insurmountable "chain of suspicion" where any two civilizations cannot communicate well enough to relieve mistrust, making conflict inevitable. Therefore, it is in every civilization's best interest to preemptively strike and destroy any developing civilization before it can become a threat, but without revealing their own location, thus explaining the Fermi paradox.