Valentine and Noonan are speculating why aliens visited Earth. It is this exchange that leads Valentine to describe the effect of their visit as the reaction of beasts and insects to the aftermath of a human picnic:
“I have to warn you, Richard, that your question falls under the umbrella of a pseudoscience called xenology. Xenology is an unnatural mixture of science fiction and formal logic. At its core is a flawed assumption – that an alien race would be psychologically human.”
“Why flawed?” asked Noonan.
“Because biologists have already been burned attempting to apply human psychology to animals. Earth animals, I note.”
“Just a second,” said Noonan. “That’s totally different. We’re talking about the psychology of intelligent beings.”
“True. And that would be just fine, if we knew what intelligence was.”
“And we don’t?” asked Noonan in surprise.
“Believe it or not, we don’t. We usually proceed from a trivial definition: intelligence is the attribute of man that separates his activity from that of the animals. It’s a kind of attempt to distinguish the master from his dog, who seems to understand everything but can’t speak. However, this trivial definition does lead to wittier ones. They are based on depressing observations of the aforementioned human activity. For example: intelligence is the ability of a living creature to perform pointless or unnatural acts.”
“Yes, that’s us,” agreed Noonan.
“Unfortunately. Or here’s a definition-hypothesis. Intelligence is a complex instinct which hasn’t yet fully matured. The idea is that instinctive activity is always natural and useful. A million years will pass, the instinct will mature, and we will cease making the mistakes which are probably an integral part of intelligence. And then, if anything in the universe changes, we will happily become extinct – again, precisely because we’ve lost the art of making mistakes, that is, trying various things not prescribed by a rigid code.”
“Somehow this all sounds so… demeaning.”
“All right, then here’s another definition – a very lofty and noble one. Intelligence is the ability to harness the powers of the surrounding world without destroying the said world.”
Noonan grimaced and shook his head. “No,” he said. “That’s a but much… That’s not us. Well, how about the idea that humans, unlike animals, have an overpowering need for knowledge? I’ve read that somewhere.”
“So have I,” said Valentine. “But the issue is that man, at least the average man, can easily overcome this need. In my opinion, the need doesn’t exist at all. There’s a need to understand, but that doesn’t require knowledge. The God hypothesis, for example, allows you to have an unparalleled understanding of absolutely everything while knowing absolutely nothing… Give a man a highly simplified model of the world and interpret every event on the basis of this simple model. This approach requires no knowledge. A few rote formulas, plus some so-called intuition, some so-called practical acumen, and some so-called common sense.”
“Wait,” said Noonan […] “Don’t get off the track. Let’s put it this way. A man meets an alien. How does each figure out that the other is intelligent?”
“No idea,” Valentine said merrily. “All I’ve read on the subject reduces to a vicious circle. If they are capable of contact, then they are intelligent. And conversely, if they are intelligent. Then they are capable of contact. And in general: if an alien creature has the honour of being psychologically human, then it’s intelligent. That’s how it is, Richard. Read Vonnegut?”
“Damn it,” said Noonan. And here I thought you’d sorted everything out.”
“Even a monkey can sort things,” observed Valentine.
Taken from pp.129-131 of Roadside Picnic by Arkady & Boris Strugatsky, tr. Olena Bormashenko. Orion, 2012. (Original Russian version 1972).