Foundation and Earth

"Come, Golan. I can't think of any trick that would allow me to predict what will happen five centuries from now."

"Nor can you think of a trick that will allow a conjurer to read the contents of a message hidden in a pseudo-tesseract on an unmanned orbiting satellite. Just the same, I've seen a conjurer do it. Has it ever occurred to you that the Time Capsule, along with the Hari Seldon simulacrum, may be rigged by the government?"

Pelorat looked as though he were revolted by the suggestion. "They wouldn't do that."

Trevize made a scornful sound.

Pelorat said, "And they'd be caught if they tried."

"I'm not at all sure of that. The point is, though, that we don't know how psychohistory works at all."

"I don't know how that computer works, but I know it works."

"That's because others know how it works. How would it be if no one knew how it worked? Then, if it stopped working for any reason, we would be helpless to do anything about it. And if psychohistory suddenly stopped working-"

"The Second Foundationers know the workings of psychohistory."

"How do you know that, Janov?"

"So it is said."

"Anything can be said. Ah, we have the distance of the Forbidden World's star, and, I hope, very accurately. Let's consider the figures."

He stared at them for a long time, his lips moving occasionally, as though he were doing some rough calculations in his head. Finally, he said, without lifting his eyes, "What's Bliss doing?"

"Sleeping, old chap," said Pelorat. Then, defensively, "She needs sleep, Golan. Maintaining herself as part of Gaia across hyperspace is energy-consuming."

"I suppose so," said Trevize, and turned back to the computer. He placed his hands on the desk and muttered, "I'll let it go in several Jumps and have it recheck each time." Then he withdrew them again and said, "I'm serious, Janov. What do you know about psychohistory?"

Pelorat looked taken aback. "Nothing. Being a historian, which I am, after a fashion, is worlds different from being a psychohistorian. Of course, I know the two fundamental basics of psychohistory, but everyone knows that."

"Even I do. The first requirement is that the number of human beings involved must be large enough to make statistical treatment valid. But how large is 'large enough'?"

Pelorat said, "The latest estimate of the Galactic population is something like ten quadrillion, and that's probably an underestimate. Surely, that's large enough."

"How do you know?"

"Because psychohistory does work, Golan. No matter how you chop logic, it does work."

"And the second requirement," said Trevize, "is that human beings not be aware of psychohistory, so that the knowledge does not skew their reactions. But they are aware of psychohistory."

"Only of its bare existence, old chap. That's not what counts. The second requirement is that human beings not be aware of the predictions of psychohistory and that they are not-except that the Second Foundationers are supposed to be aware of them, but they're a special case."

"And upon those two requirements alone, the science of psychohistory has been developed. That's hard to believe."

"Not out of those two requirements alone, " said Pelorat. "There are advanced mathematics and elaborate statistical methods. The story is-if you want tradition-that Hari Seldon devised psychohistory by modeling it upon the kinetic theory of gases. Each atom or molecule in a gas moves randomly so that we can't know the position or velocity of any one of them. Nevertheless, using statistics, we can work out the rules governing their overall behavior with great precision. In the same way, Seldon intended to work out the overall behavior of human societies even though the solutions would not apply to the behavior of individual human beings."

"Perhaps, but human beings aren't atoms."

"True," said Pelorat. "A human being has consciousness and his behavior is sufficiently complicated to make it appear to be free will. How Seldon handled that I haven't any idea, and I'm sure I couldn't understand it even if someone who knew tried to explain it to me-but he did it."

Trevize said, "And the whole thing depends on dealing with people who are both numerous and unaware. Doesn't that seem to you a quicksandish foundation on which to build an enormous mathematical structure? If those requirements are not truly met, then everything collapses."

"But since the Plan hasn't collapsed-"

"Or, if the requirements are not exactly false or inadequate but simply weaker than they should be, psychohistory might work adequately for centuries and then, upon reaching some particular crisis, would collapse-as it did temporarily in the time of the Mule. Or what if there is a third requirement?"

"What third requirement?" asked Pelorat, frowning slightly.

"I don't know," said Trevize. "An argument may seem thoroughly logical and elegant and yet contain unexpressed assumptions. Maybe the third requirement is an assumption so taken for granted that no one ever thinks of mentioning it."