A work of philosophy, mostly epistemology, with a bit of quantum physics thrown in. The theme is that all problems are solvable—“anything not forbidden by the laws of nature is achievable, given the right knowledge”—but that there is no end of problems or solutions, just as there is no end to knowledge or to mistakes. In contrast to both skepticism and “inductionism”, Deutsch promotes “fallibilism”.
I found this book fascinating and agree with much of it, although I disagree with many formulations, especially around induction and the base of knowledge. That said, it was one of those books where, even though I felt that I knew many of the points before I read them, I have found that the formulations have stuck with me, such that I am continually referring to the book and suggesting it to others. I particularly liked his identification that solutions always create new problems, which we meet with new solutions. Often people complain that a given solution created new problems, as if that is an indictment of the solution; when I encounter that argument, I now point them to Deutsch and explain that that is the nature of solving problems.
Recommended for the general reader.