Phineas Gage is the central figure in the book. All the book’s scientific questions are organized around him. In 1848, Gage was a foreman at a railroad construction company in Vermont when he suffered a severe head injury while attempting to blast rock. A tamping iron went through his skull and brain, and the resulting injuries made him a legendary figure in neuroscience. His survival of the accident, followed by apparent changes in his personality and judgment, offered evidence regarding how the brain affects behavior.

Through Gage, Fleischman explores the theme of One Case, Different Interpretations. Doctors, phrenologists, neurologists, and eventually neuroscientists interpreted Gage’s case differently. Consequently, Gage was transformed from an individual who had experienced an extraordinary injury into a test case.

Dr. Harlow was Gage’s treating physician immediately following the accident and went on to serve as a key witness to the case. Dr. Harlow saw Gage both during the initial medical crisis and during his subsequent recovery. He contributed much of the information available today about the changes in Gage’s behavior and personality.

Dr. Harlow represents the limited aspects of medicine during the mid-19th century, as he worked without much of the knowledge we have today, like germ theory and antibiotics. Despite this, he helped Gage recover from an injury that likely should have resulted in his death. Dr. Harlow’s later accounts illustrate how physical recovery doesn’t always result in complete psychological recovery. His observations suggest that damage to certain areas of the brain can lead to changes in thinking, planning, and interpersonal behaviors.

Dr. Bigelow was a Boston surgeon who helped popularize Gage’s medical case among a wider audience. When Gage arrived in Boston for treatment, Dr. Bigelow evaluated Gage, introduced him to other medical professionals, and helped make the case internationally recognized. He used Gage’s case to argue against previously held assumptions about brain structure. His interest in Gage reveals a key message of the book: Gage was both a person who experienced a catastrophic brain injury and a specimen who was studied and observed by physicians eager to use his case to support their theoretical positions.

Paul Broca is a leading figure in neuroscience presented in the latter portion of the book. His research moved brain science toward a greater degree of precision regarding issues related to localization. Broca gained international recognition for establishing that a location in the left frontal lobe—now referred to as Broca’s area—is specifically responsible for producing spoken words. Broca’s work demonstrated that sections of the brain correspond with specific functions.

Gage’s case raised questions about whether there are separate functional zones within different areas of the brain. Broca’s discovery facilitated development of a more systematic approach for researching brain function.

Carl Wernicke was another scientist whose work explored regional specialization within the brain. Wernicke identified a section of the brain that he believed was connected to comprehending language, later designated Wernicke’s area. In conjunction with Broca’s research, Wernicke established how there is localized specialization within various areas of the brain.

By discussing Wernicke and others, Fleischman illustrates how neuroscience develops incrementally. Researchers build upon prior knowledge and cases, revisit previous theories using improved data, and refine prior queries using better methodologies. While Wernicke didn’t play a role in Gage’s personal life directly, he sustained the impact of Gage’s case across decades within medicine and psychology.

Antonio Damasio is a modern neuroscientist. Using subjects with damage to their frontal lobe, he demonstrated that individuals can maintain relatively high levels of cognitive ability for many tasks while exhibiting serious impairments in judgmental reasoning, emotional responses, and interpersonal decision-making skills. Antonio considers Gage relevant to modern neurological practices.

Through Antonio and his wife Hanna’s research, Fleischman bridges a 19th-century case history and 20th-century neuroscientific inquiry. Ultimately, the Damasios’ work enables Fleischman to connect one isolated accident to a larger modern paradigm regarding how brains control personalities and everyday decision-making abilities.