The title sounds like a silly self-help book, but the real scope of Michael S. Gazzaniga's Who's in Charge? is huge—it tackles the age-old debate of free will. And while it could easily be sheerly academic and overwrought, Gazzaniga does a good job making you care, insisting there's more at stake than you think. He broaches his question gracefully, with humor and a conversational tone, while still keeping the details; in the end he provides an answer by essentially throwing out the question altogether.

Gazzaniga has mega credentials. He's the founder of cognitive neuroscience. He discovered the split-brain phenomenon (now a part of pop culture—the idea that the left and right sides of the brain serve different functions). He's also the guy who discovered the "interpreter," a relentless piece of our brains that insists on constructing narratives.

His most recent book is the result of a 2009 Gifford Lecture (the great Scottish series devoted to the intersection of science and theology—past lecturers have included Niels Bohr, Richard Dawkins, and Carl Sagan). The author relies on not only his history in neuroscience, but also physics, philosophy, and ethics to reach his contentious finale. There are a lot of fun factoids in general, but the really juicy stuff is in the final chapter of the book, which explores the implications of free will within our judicial system.

In contemporary times, determinism has swept our thinking. Thanks to neuroscience we know that our brains work automatically, manipulating our body without much of our awareness (think of Freud's iceberg metaphor: the tip above the water is our consciousness, the hunk below is the unconscious). The book's main query is: What does it mean for our systems of rules and regulations, if we believe our actions are predetermined? If criminals operate automatically, what is fair and effective punishment?

Perhaps controversially, Gazzaniga opposes things like the insanity defense and softer punishment on youth. The concept of responsibility, he argues, does not exist in any particular location in the brain; responsibility is a contract, an invented interaction between people. Just like morality does not exist at some point within the brain—it can be learned by anyone, anytime. (The logic being: If there were only one person in the entire world, would morality still exist? No, he says.)

This idea is major. As it turns out, our understanding of the mind and its limitations directly affects how we act. To prove this, the author points to a recent series of studies where test subjects were primed with uplifting/positive rhetoric and determinist rhetoric, then put to a task. Those primed with positive language played by the rules; the subjects primed with deterministic rhetoric cheated. The conclusion: People "act better if they believe they have free will." This is among the most surprising aspects of the book—all of the evidence cited for how unfixed and completely permeable our minds are.

The convincing, final word is that the concept of free will itself is arcane and miscast. There is no central control system within the brain. Although it feels like we have a chief operator (a "soul," or "homunculus"), the mind is a complex system that is not even self-contained; it's determined by a layering of society, genes, and life experiences. Who's in Charge? may be a short book, about 200 pages, but it offers a lot to consider about what Gazzaniga deems the "scientific problem of the century."