Re: Nice reference
"psychohistory", a set of methods which could be used to manipulate the behaviour of large populations without their knowledge
LOLNO!! "psychohistory" was not about "manipulating populations" at all. It was about predicting what history has in store given the present political "state of things".
This is of course fanciful to the utmost as one cannot even predict the weather pattern one week out, and, as anyone how has glanced at von Mises realizes, history or economics are not physical system allowing scientific predictions, let alone tests. So stuff that. But this is Sci-Fi, so why not.
Now, if your psychohistory was working, you could position yourself NOW so that natural development of events lead to a preferred outcome in THE FUTURE. Thus, setting up a gaggle of archivists at the edge of the Galaxy would lead to new Galactic Empire in a few thousand years with high probability.
This probability being not 100%, it turns out that one has to finagle things behind the scenes using the "Second Foundation". In modern parlance, hack. Sadly, this is underwhelmingly done using another magic device, telepathy.
If suspension of disbelief is used, one could consider that psychistory sees history as a cellular automaton. One can then do a few billion runs of "history in the box" and select an outcome advantageous to oneself, then change a couple of cells at the NOW...
IIRC Sheldon could do the predictions using a slide ruler. Talk about "underspecified boundary conditions" doesn't even being to describe this kind of Mathematical Magic.