Book excerpt: OVER THE LAST CENTURY scientists have made tremendous strides in understanding the physical nature of the universe and the biochemical nature of life. Yet the most salient feature of individual lives--our day-to-day consciousness and experience of the world, or "sentience"--remains stubbornly immune to scientific explanation. This divide is called the "mind-body problem," and it is centuries old. In this book, author Carey Carlson performs two valuable tasks. First, he lays out the mind-body problem in crystalline common-sense prose. Second, he proposes an intriguing solution based on the work of early-twentieth-century philosophers Bertrand Russell and Alfred North Whitehead. This book will be of interest both to general readers of science and philosophy and to those steeped in the literature. The second edition includes additional arrow diagrams in Chapter 5 that fortify Russell and Whitehead's view of physics as a causal web of time-ordered events.