On Being Certain is among the most useful books I read this year. I am not putting it on my best-of-the-year list, because the list is already too long, and the book is longer than its topic is.
On being certain is a tour of what people now know about how the mind works. There's all sorts of interesting stuff in there, but the summary comes down to...the mind doesn't work how you think it does. It doesn't even work in a way that is compatible with how you experience the world.
Perhaps the most interesting factoid in the book: The mind is well known to actively re-arrange the time-order of events in your head. If you see a kid fall in the water, you think about it, then jump in to save. If you see a baseball coming towards you, the batter, you decide whether to swing, then swing. Nonsense. The decision to swing, or to jump in the water after a kid is made and acted upon before the thinking part of the brain receives the message. After the fact, the brain fills in the explanation for why one did what one did. And then you, the actor, think and tell other people what your brain made up to cover for your acting first and thinking second. This applies to all sorts of stuff.
The target point of the book, finished after nearly 200 pages of discussion about how the mind doesn't work how you think it does, is that certainty is not a cognitive state. It is an emotional state. And the emotional experience of certainty is managed entirely separately from the cognitive understanding. Which means that certainty can be felt (very easily) without truth, and truth can be apprehended clearly without feelings of certainty. Takeaway: the sense of certainty tells you NOTHING useful about the truthiness of a proposition.
Lots of other good info in the book. The religious-experience center of the brain is hit on.
Question for the reader: assume that if you act/decide quickly, your brain is lying to you about whether you acted first or thought first. Assume also that the "why" constructed after the action is a semi-pure fabrication. How does that change your life?