In this work synthesizing thirty years of research, psychologist, historian of science, and the world's best-known skeptic Michael Shermer upends the traditional thinking about how humans form beliefs about the world. Simply put, beliefs come first and explanations for beliefs follow. The brain, Shermer argues, is a belief engine. From sensory data flowing in through the senses, the brain naturally begins to look for and find patterns, and then infuses those patterns with meaning. Our brains connect the dots of our world into meaningful patterns that explain why things happen, and these patterns become beliefs. Once beliefs are formed the brain begins to look for and find confirmatory evidence in support of those beliefs, which accelerates the process of reinforcing them, and round and round the process goes in a positive-feedback loop of belief confirmation. Shermer outlines the numerous cognitive tools our brains engage to reinforce our beliefs as truths.

Interlaced with his theory of belief, Shermer provides countless real-world examples of how this process operates, from politics, economics, and religion to conspiracy theories, the supernatural, and the paranormal. Ultimately, he demonstrates why science is the best tool ever devised to determine whether or not a belief matches reality.