Algorithms to Live By by Brian Christian and Tom Griffiths is a book written for a general audience about a number of ideas in computer science and how they are applied in practice. Despite the widespread interest in all things related to computers, very few such books have been written, and I know of no others that cover the particular subjects included here. The book gives clear, almost entirely math-free, accounts of the ideas; narrates their historical development, enlivened with many personal anecdotes1; and describes a variety of applications. The applications fall into three categories. First, there are applications within computer technology itself; unsurprisingly, these form the majority of the applications discussed in the book. Second, there are applications in commercial or institutional settings; for instance, there is a fascinating discussion of techniques for testing new medical treatments which balance the need for control groups in reliable experiments against the problems involved in denying control subjects the new treatments that they need. Finally, there are applications that are presented as solutions to everyday problems that arise for the man on the street. These last seem to me the least successful aspect of the book. A few seem interesting, such as deliberately introducing random elements into projects you are working on. Most of them I find unconvincing, and a couple, which I will discuss below, seem to me completely crazy. Finally, the authors argue that there is reason to believe that people in any case naturally use these kinds of ideas in their ordinary thinking and action. Some of this seems to me reasonable; much of it seems to me overstated. I will discuss this in section 4. The authors’ view of their own work is very different. As the book title indicates, they consider that the central point of the book is precisely the application of computer science to everyday problems. Moreover, Christian and Griffiths claim optimistically that “looking through the lens of computer science can teach us about the nature of the human mind, the meaning of rationality, and the oldest question of all: how to live.” I agree that the ideas are somewhat relevant to the meaning of rationality and to the question of how to act sensibly in various situations (“how to live” is a rhetorical exaggeration). However, I am skeptical that the ideas are very helpful in understanding the nature of the human mind; the problems that they address are a small and rather eccentric selection of the tasks faced by human cognition.