Asimov continues with his narration of the history of the interregnum between empires in pretty much the same anthology format used in Foundation. Actually, upon further thinking, there's probably no way really to tell the story of a 1,000 year journey on the part of humanity without doing it in snippets. More and more the series begins to read more like a history book with some dramatic events being highlighted for their importance as turning points. These turning points are called Seldon Crises, foreseen events by Hari Seldon, Psychohistorian, which impel the people of the Foundation forward to galactic dominance. Throughout the first book and a half, Asimov establishes a bit of fatalism - nothing can stop the foundation by historical imperative, and for that reason the people of the Foundation, especially it's leadership, become apathetic.
Asimov throws a wrench into the status quo with the rise of a mutant, a statistical improbability and anomaly that could not possibly be accounted for in the creation of the Seldon Plan and therefore the first truly unknown quantity with the ability to destroy the Foundation. This mutant, called the Mule, has psychic ability and the great revival of technology in the Foundation is powerless to stop him from manipulating people and working his way to dominance. The Mule consolidates his power, takes over the Foundation and destroys the remnants of the former galactic empire and it looks like Seldon's prophecies could be wrong. That a single individual upset the 1,000 year plan to turn the Foundation into the Second Empire, in only 5 years.
Asimov again explores the themes of individuality, stagnation, complacency and religion. Choice and free will are major foci for the novel. If the Seldon Plan is mathematically and psychologically accurate like a prophecy, if certain things are meant to happen, just because human beings will predictably react in the same ways in given situations, do we really have free will? What is the role of the individual in society in in the historical process? Asimov treats history like a Marxist, influenced by Hegelian dialectics. Conflicts and crises between opposing forces give birth to a third new status quo until it comes into conflict with an opposing force. These moments of intersection are the Crises predicted by Seldon and the focus of Asimov's 1,000 year narrative. But the Mule changes that. He challenges the notion of inevitability and proves the fallibility of Seldon's prophecies. But by doing so he introduces another free will paradox. The Mule has the ability to modify emotions and create complete loyalty in people. He wins victories by converting the opposing sides' generals and leaders into giving up and then serving him, destroying free will again by creating it out of the tight confines of the Seldon Plan. It's truly and interesting concept. How will the Mule be stopped? Enter: the Second Foundation. Established on the other side of the galaxy as a failsafe in case of the failure of the Foundation. But no record exists of where that foundation is or what type of society it will become. Will the Mule find it and destroy it? Does it exist after 300 years?
My major problem throughout the narration is that it is assumed that the Seldon Plan represents the ideal in some way. Seldon was a human being, capable of manipulating and creating situations a millennia in advance and manipulating the fate of quadrillions of human beings. Who says his plan needs to be fulfilled? What if people don't want Seldon's future? What if they don't want to live in an all-encompassing empire? I would maybe believe Asimov wants you to question that, but he gives himself away in little asides in the narration, inserting emotional declamations against the upset of the Plan.