Chapter 4

PSYCHOHISTORY?..Gaal Dornick,  using nonmathematical concepts, has definedpsychohistory  to  be  that  branch of  mathematics  which  deals with  thereactions of  human conglomerates to fixed  social and economic stimuli....
...  Implicit in  all these  definitions is  the assumption that  the humanconglomerate being  dealt with is sufficiently  large for valid statisticaltreatment. The  necessary size of such a  conglomerate may be determined bySeldon's First Theorem which ... A further necessary assumption is that thehuman conglomerate  be itself  unaware of psychohistoric  analysis in orderthat its reactions be truly random ...
The basis of all valid psychohistory lies in the development of the Seldon.
Functions which  exhibit properties  congruent to those of  such social andeconomic forces as ...
ENCYCLOPEDIA GALACTICA"Good afternoon, sir," said Gaal. "I?I?
"You didn't think we were to meet before tomorrow? Ordinarily, we would nothave. It is just that if we are to use your services, we must work quickly.
It grows continually more difficult to obtain recruits.""I don't understand, sir.""You  were  talking to  a  man on  the  observation tower,  were you  not?""Yes.  His   first  name   is  Jerril.  I   know  no  more   about  him.  ""His name is nothing. He is an agent of the Commission of Public Safety. Hefollowed you from the space-port.""But why? I am afraid I am very confused.""Did the man on the tower say nothing about me?"Gaal hesitated, "He referred to you as Raven Seldon.""Did he say why?""He said you predict disaster.""I do. What does Trantor mean to you?"Everyone seemed to be asking his opinion of Trantor. Gaal felt incapable ofresponse beyond the bare word, "Glorious.""You say that without thinking. What of psychohistory?""I haven't thought of applying it to the problem.""Before  you  are  done  with  me,  young  man,  you will  learn  to  applypsychohistory  to all  problems as a  matter  of course.  朞bserve." Seldonremoved his calculator pad from the pouch at his belt. Men said he kept onebeneath  his pillow  for use  in moments  of wakefulness. Its  gray, glossyfinish was slightly worn  by use. Seldon's nimble fingers, spotted now withage, played  along the files and  rows of buttons that  filled its surface.
Red symbols glowed out from the upper tier.
He  said,  "That  represents  the  condition  of the  Empire  at  present."He waited.
Gaal  said  finally,  "Surely  that  is  not  a  complete  representation.""No,  not complete,"  said Seldon.  "I am  glad you  do not accept  my wordblindly. However, this is  an approximation which will serve to demonstratethe proposition. Will you accept that?""Subject to my later  verification of the derivation of the function, yes."Gaal was carefully avoiding a possible trap.
"Good.  Add  to  this  the  known probability  of  Imperial  assassination,viceregal  revolt,  the  contemporary  recurrence of  periods  of  economicdepression,  the  declining  rate  of  planetary explorations,  the.  ...."He proceeded. As each item was mentioned, new symbols sprang to life at histouch,  and melted  into  the basic  function which  expanded  and changed.
Gaal  stopped   him  only  once.   "I  don't  see  the   validity  of  thatset-transformation."Seldon repeated it more slowly.
Gaal  said,  "But that  is  done  by way  of  a forbidden  sociooperation.""Good. You are quick, but not yet quick enough. It is not forbidden in thisconnection. Let me do it by expansions."The procedure was much longer and at its end, Gaal said, humbly, "Yes, Isee now."Finally, Seldon stopped. "This is Trantor three centuries from now. How doyou interpret that? Eh?" He put his head to one side and waited.
Gaal said, unbelievingly, "Total destruction! But ?but that is impossible.
Trantor has never been ?
Seldon was filled with the intense excitement of a man whose body only hadgrown old. "Come, come. You saw how the result was arrived at. Put it intowords. Forget the symbolism for a moment."Gaal said, "As Trantor becomes more specialized, it be comes morevulnerable, less able to defend itself. Further, as it becomes more andmore the administrative center of Empire, it becomes a greater prize. Asthe Imperial succession becomes more and more uncertain, and the feudsamong the great families more rampant, social responsibility disappears. ""Enough. And what of the numerical probability of total destruction withinthree centuries?""I couldn't tell.""Surely you can perform a field-differentiation?"Gaal felt himself under pressure. He was not offered the calculator pad. Itwas held a foot from his eyes. He calculated furiously and felt hisforehead grow slick with sweat.
He said, "About 85%?""Not bad," said Seldon, thrusting out a lower lip, "but not good. Theactual figure is 92.5%."Gaal said, "And so you are called Raven Seldon? I have seen none of this inthe journals.""But of course not. This is unprintable. Do you suppose the Imperium couldexpose its shakiness in this manner. That is a very simple demonstration inpsychohistory. But some of our results have leaked out among thearistocracy.""That's bad.""Not necessarily. All is taken into account.""But is that why I'm being investigated?""Yes. Everything about my project is being investigated.""Are you in danger, sir?""Oh, yes. There is probability of 1.7% that I will be executed, but ofcourse that will not stop the project. We have taken that into account aswell. Well, never mind. You will meet me, I suppose, at the Universitytomorrow?""I will," said Gaal.