What are the motifs in Prelude to Foundation by Isaac Asimov?

Power is a recurring idea in the narrative. Hari Seldon's "flight" around Trantor is largely about who will enjoy the power of psychohistory, once he has turned the theoretical into the practical. His paper at the Decennial Mathematics Convention makes clear (he believes) that this is a strictly theoretical field; its scope-the twenty-five million inhabited worlds of the Galactic Empire-is too vast to be covered in several lifetimes, and by the time the fastest computer delivers an answer to a question, it is obsolete. No one in power hears Seldon, however. The Empire has been degenerating for decades and its downfall seems likely. Emperor Cleon I, wants a tool that can prevent this. His more practical chief of staff, Eto Demerzel, wants at least to ameliorate the effects of the break-up. Hearing Seldon proclaim he cannot deliver such a tool, they put him under reconnaisance and Demerzel is prepared to "eliminate" Seldon should a "competitor" try to control him.