Cixin Liu - The Dark Forest

“Yeah. That’s an easy feeling to find in a dark place like this.”

“Let’s call these two civilized worlds your civilization and my civilization. They’re separated by a great distance, say, a hundred light-years. You can detect that I exist, but you don’t know any details. However, I’m completely ignorant of your presence.”

“Right.”

“Now we need to define two concepts, ‘benevolence’ and ‘malice’ between civilizations. These words themselves aren’t very rigorous in a scientific context, so we’ve got to restrict their meaning. ‘Benevolence’ means not taking the initiative to attack and eradicate other civilizations. ‘Malice’ is the opposite.”

“That’s a low bar for benevolence.”

“Next, consider your options for dealing with me. Please remember that the axioms of cosmic civilization should be kept in mind throughout the process, as well as the distance scale and the environment of space.”

“I could choose to communicate with you.”

“If you do that, you should be aware of the price you’ll pay: You’ll have exposed your existence to me.”

“Right. In the universe, that’s no small thing.”

“There are different degrees of exposure. The strongest form of exposure is when I know your precise interstellar coordinates. Next is when I know your general direction, and the weakest is when I only know of your existence. But even the weakest form of exposure makes it possible for me to search for you, because since you’ve detected my existence, I know that I’ll be able to find you. It’s only a matter of time, from the standpoint of technological development.”

“But my boy, I could still take the risk to talk to you. If you’re malicious, then it’s my bad luck. But if you’re benevolent, then we could have further exchanges and ultimately be united into a benevolent civilization.”

“Okay, Da Shi. Now we’ve come to the crux of it. Let’s return to the axioms of cosmic civilization: Even if I’m a benevolent civilization, can I determine at the start of our communication whether or not you are also benevolent?”

“Of course not. That would violate the first axiom.”

“So once I’ve received your message, what should I do?”

“Naturally, you ought to determine whether I’m benevolent or malicious. Malicious, and you eradicate me. Benevolent, and we can continue communicating.”

The flame on Luo Ji’s side rose up and moved back and forth. Evidently he had gotten up and was pacing. “That’s fine on Earth, but not out in the universe. So next we’ll introduce an important new concept: the chain of suspicion.”

“That’s an odd term.”

“The term is all I had at first. It wasn’t explained to me. But, later, I was able to infer its meaning from the words themselves.”

“Who didn’t explain it?”

“…I’ll tell you later. Let’s continue. If you think I’m benevolent, that’s not a reason to feel safe, because according to the first axiom, a benevolent civilization can’t predict that any other civilization is benevolent. You don’t know whether I think you’re benevolent or malicious. Next, even if you know that I think you’re benevolent, and I also know that you think I’m benevolent, I don’t know what you think about what I think about what you’re thinking about me. It’s convoluted, isn’t it? This is just the third level, but the logic goes on indefinitely.”

“I get what you mean.”

“That’s the chain of suspicion. It’s something that you don’t see on Earth. Humanity’s shared species, cultural similarities, interconnected ecosystem, and close distances means that, in this environment, the chain of suspicion will only extend a level or two before it’s resolved through communication. But in space, the chain of suspicion can be very long. Something like the Battle of Darkness will already have taken place before communication can resolve it.”

Shi Qiang took a drag on his cigarette, and his contemplative face emerged from the darkness for a moment. “It looks now like the Battle of Darkness has a lot to teach us.”

“That’s right. The five ships of Starship Earth formed a quasi-cosmic civilization, not a real one, because they consisted of a single species—humans—who were very close to each other. But even so, when they were dealt that dead hand, the chain of suspicion emerged. In actual cosmic civilization, the biological differences between different groups might be as high as the kingdom level, and cultural differences are even further beyond our imagining. Add to this the vast distances between them, and you have chains of suspicion that are practically indestructible.”

“That means that the outcome is the same, regardless of whether we’re benevolent civilizations or malicious civilizations?”

“That’s right. That’s the most important aspect of the chain of suspicion. It’s unrelated to the civilization’s own morality and social structure. It’s enough to think of every civilization as the points at the end of a chain. Regardless of whether civilizations are internally benevolent or malicious, when they enter the web formed by chains of suspicion, they’re all identical.”

“But if you’re much weaker than I am, you’re not a threat to me. So I could always communicate with you, right?”

“That won’t work, either. Here we need to introduce a second important concept: the technological explosion. I didn’t get a full explanation for this, either, but it was far easier to infer than the chain of suspicion. Human civilization has five thousand years of history, and life on Earth might be as much as a few billion years old. But modern technology was developed over the course of three hundred years. On the scale of the universe, that’s not development. It’s an explosion! The potential for technological leaps is the explosive buried within every civilization, and if it’s lit by some internal or external factor, it goes off with a bang. On Earth it took three hundred years, but there’s no reason why humanity should be the fastest of all cosmic civilizations. Maybe there are others whose technological explosions were even more sudden. I’m weaker than you, but once I’ve received your message and know of your existence, the chain of suspicion is established between us. If at any time I experience a technological explosion that suddenly puts me far ahead of you, then I’m stronger than you. On the scale of the universe, several hundred years is the snap of a finger. And it might be that my knowledge of your existence and the information I received from our communication was the perfect spark to set off that explosion. That means that even though I’m just a newborn or growing civilization, I’m still a big danger to you.”

Shi Qiang watched Luo Ji’s flame in the darkness as he thought for a few seconds, then looked at his own cigarette. “So I have to keep quiet.”

“Do you think that will work?”

They smoked. The balls of flame brightened and their faces emerged from the darkness like the gods of this simple universe, deep in thought.

Shi Qiang said, “No, it won’t. If you’re stronger than me, then since I was able to find you, one day you’ll be able to find me. And then there will be a chain of suspicion between us. If you’re weaker than me, you could experience a technological explosion at any time, and that would take us back to the first case. To sum up: one, letting you know I exist, and two, letting you continue to exist, are both dangerous to me and violate the first axiom.”

“Da Shi, you’ve really got a clear mind.”

“My brain can keep up with yours so far, but we’re only getting started.”

Luo Ji was silent in the dark for a long time. His face emerged in the weak light of the ball of flame two or three times before he said, “Da Shi, this isn’t a start. Our reasoning has already reached a conclusion.”