The first book is about trust, the belief in something in the absence of understanding.
The Royal Society was founded in 1660, with the motto Nullius in Verba, "On No One's Word". The promise of science was that it would be a method for discovering truth without needing to trust anyone: because experiments can and would be replicated, incorrect theories and incorrect information would be !ltered out. By exploring systems that could be understood in full, scientists eventually made breakthroughs in our understanding of every part of the natural world.
You might hope that this sort of understanding can be expanded further — that you could come to understand every part of the world, look inside to see how it works, and personally arrive at true beliefs about it. This hope would be wrong. To understand everything in the world would take an amount of time many orders of magnitude more than historical human lifespans.
In place of being able to understand any system, we have its lowly sibling, trust. Can I believe what this paper is telling me, when I don't have time to replicate its results or even read every page? Can I trust my emotions when I don’t know where they come from? Some code on StackExchange I haven’t read?
A trained machine learning system off-distribution? These are questions where we can't feasibly get a repeatable, replicable setup. The essays in this book explore the judgments we make about how to decide which sources to trust, when building our models of the world and acting upon it.