An attempt to understand the human brain, including consciousness, via the nervous system. Even the mathematics of the brain is dauntingly complex: It houses about 90 billion neurons, and in merely one section of the nervous system, there are about 250,000 different neural input connections. However, it’s estimated that there are only 20,000 genes in a human body, and possibly 10,000 to 15,000 provide instructions governing the operation of the brain. According to Adams, those instructions are, therefore, necessarily as efficient as they are general. His overarching purpose is to explain (or, more precisely, hypothesize) how the brain, given such a limited set of instructions, is able to perform complex operations like the development of reflexes, the exercise of judgment, and the emergence of consciousness. The author describes the early embryonic development of the nervous system and its successive maturation to increasing levels of sophistication, what Adams calls “bootstrapping.” This process ultimately produces the stunningly labyrinthine “biological machine” that supports motor coordination, emotion, memory, and decision-making—functions that express themselves at both the conscious and subconscious levels. The author also tackles perennially controversial issues like the nature of consciousness, which he explains as the ability to differentiate and recognize different sensory perceptions. Along the way, Adams furnishes an anatomical tour of the brain’s inner machinations, replete with helpful diagrams to explain the interactions among its various parts. The author has a doctorate in neuroscience from UCLA’s Brain Research Institute, and the depth and breadth of his expertise are apparent on every page. He writes in what is likely the most accessible language available to adequately describe such a prohibitively challenging thesis, meaning there are still plenty of sentences like this one: “The neurotransmitter molecules are packaged inside vesicles within neurons and are expelled from axon terminals via the process of exocytosis.” Also, he skirts rather than confronts some of the principal philosophical problems regarding the relationship between the brain and consciousness by reducing all intentional choice to the brain’s circuitry. Still, Adams supplies a provocative set of original arguments that deserves attention. An exhilarating contribution to the debate regarding the brain’s inner workings.