The prefrontal cortex of the brain enables people to have and maintain religious beliefs. Not surprisingly, a lesion in the dorsolateral prefrontal cortex (dlPFC), due to something like a traumatic brain injury, a psychological disorder, a drug or alcohol addiction, or simply a particular genetic profile, is associated with religious fundamentalism (or the narrowing of religious beliefs to exclude diversity of thought). Those with brain damage to the prefrontal cortex exhibit a significant decrease in cognitive flexibility and openness to other viewpoints. Cognitive flexibility refers to the brain’s ability to easily switch from thinking about one concept to another, and to think about multiple things simultaneously. Cognitive flexibility allows organisms to update beliefs in light of new evidence. Cognitive flexibility and openness are necessary for flexible and adaptive religious commitment, and such diversity of religious thought is dependent on proper dlPFC functionality. Of course, cognitive flexibility and openness aren’t the only things that make brains susceptible to religious fundamentalism. In fact, an impaired prefrontal cortex may account for only a fifth of the variation we see in religious fundamentalism scores.