A few years ago I read Cixin Liu's Remembrance of Earth's Past trilogy (The Three Body Problem, The Dark Forest, and Death's End) and I recently revisited it in audiobook format. The Dark Forest is my favorite in the trilogy because it touches on so many different ideas. The title of the book comes from the dark forest hypothesis, a solution to the Fermi paradox - which is the contradiction between the high probability of extraterrestrial civilizations existing in the universe and the lack of evidence they exist.
The dark forest hypothesis suggests that many alien civilizations exist in the universe, but are silent and thus undetectable out of fear of being destroyed by other hostile civilizations. These silent civilizations may also be "hunters" themselves in that when they detect another civilization, they attack and destroy it.
The framework for cosmic sociology is introduced in the book and explains how a dark forest universe would come about. Cosmic sociology simply refers to the study of how intelligent civilizations might interact on a cosmic scale. The dark forest hypothesis is born out of cosmic sociology.
Suppose that survival is the primary need of every civilization. Civilizations are likely to expand. Resources in the universe are finite. Destroying any potential rival civilization ensures access to resources and the continued survival of the civilization.
A Hobbesian trap explains another reason why preemptive strikes occur between two civilizations. The chain of suspicion, as Cixin Liu describes, both sides fear imminent attack from the other and therefore will seek to destroy the one another. A civilization cannot be certain that another civilization is not hostile, or may not one day become hostile. If guaranteed survival of your civilization is the goal, a preemptive strike is a rational course of action.
Here's an excerpt from the book:
Because they don’t know what we’re thinking.
Suppose they know that we’re not devils?
The problem still exists.
They don’t know what we’re thinking about them.
They don’t know what we’re thinking about what they’re thinking about us.
That carries on in an endless chain of suspicion: They don’t know what we’re thinking about what they’re thinking about what we’re thinking about what they’re thinking about what we’re...
The explanation for why we don't see other civilizations in the universe is because they're intentionally hiding themselves. This hiding is because of the perception that any other civilization would be a potential threat to their own, likely destroying any other civilizations they come across.
The book also touches on the Berserker hypothesis, another solution to the Fermi Paradox, and similar to the dark forest hypothesis with some overlap. The hypothesis suggests that the reason why we don't detect other civilizations is because they've all been wiped out by another highly aggressive force via destructive Von Neumann probes. This force could be an expansionist civilization that wants to wipe out any and all competition, or anything that could be a threat to their continued existence. Or it may not even be an expansionist civilization, but an artificial intelligence.
Although I tend to be agnostic toward these ideas, I love to think about them. Personally, I don't believe that the universe is teeming with life, at least not in a way where we would be able to meaningfully contact each other. Life itself is an exceptionally rare occurrence, and it when life does emerge, it's extremely unlikely that that life is intelligent enough to be capable of science, technology, interstellar travel, etc. Civilizations with these capabilities are separated by an infinitely vast amount of space and time.
Thanks for reading. Feel free to send comments, questions, or recommendations to hey@chuck.is.