In a flashback, Menakem remembers his grandmother soothing herself by humming, singing, and rocking in a chair. She knew how to settle her soul nerve–the unifying organ of the nervous system. The soul nerve stretches through most of the body from the throat to the gut. It is the largest organ in the body’s autonomic nervous system. Through vibes and sensations, the soul nerve not only communicates between different parts of the body but also from person to person.

The soul nerve connects directly to the lizard brain. Although aspects of how it functions remain unknown, the soul nerve is where humans experience strong emotions, such as love, fear, grief, and disgust. The soul nerve is vital to health and well-being, regulating breathing, heart rate, and blood pressure, as well as preventing inflammation and reducing pain. It is also responsible for making the body relax or freeze. These responses are largely outside conscious control.

However, one can learn to relax the muscles and settle the body through soul nerve training. Menakem guides readers through a series of exercises aimed at soothing the body during stressful situations. Among these are humming, belly breathing, buzzing, slow rocking, and chanting.