This book rejects traditional, dominant—typically reductive and anti-realist—explanations of stress, PTSD, and resilience. Frank Tortorello presents the United States Marine Corps’ doctrinal explanation of stress, PTSD, and resilience as a case in point using new realist theoretical resources from Rom Harré and Charles R. Varela. The author systematically exposes the scientific and ethical failures of traditional explanations in accounting for the actions of stressed and resilient Marines on and off the battlefield. The power of new realist explanations emerges in application to the same ethnographic data, thereby supporting the author’s call to replace traditional explanations with those grounded in new realism.