Ezekiel is an oncologist, bioethicist, and health-policy expert who served as an architect of the Affordable Care Act. He uses his medical experience to challenge the modern wellness industry, categorizing much of its advice as expensive and unproven. He advocates for a practical approach to longevity that prioritizes emotional and psychological well-being over physical data-tracking.

Benjamin Franklin is a Founding Father of the United States who lived productively into his eighties. After retiring from his printing business, he invented bifocals, negotiated the Treaty of Paris, and founded various civic institutions. He represents the ideal of using a long life for personal growth, friendship, and societal betterment rather than simply existing.

Benjamin is a pediatrician and Ezekiel's late father. He serves as the personal and philosophical anchor for the book's framework. His blunt advice to avoid self-destructive risks and his natural sociability form the basis for the first two rules of his son's wellness philosophy.

Aristotle is an ancient Greek philosopher who explored the ethical dimensions of human flourishing. He dedicated two full chapters of his *Nicomachean Ethics* to the nature of friendship. His assertion that humans are naturally social animals provides historical weight to the contemporary argument that relationships are central to physical health.

Robert is a professor of psychiatry at Harvard University and the director of the Harvard Study of Adult Development. His work involves overseeing an 85-year longitudinal study on human aging. His research provides the definitive empirical evidence that warm social connections are the strongest predictor of a long, happy life.

Robin is an evolutionary psychologist at the University of Oxford. He studies human social networks and developed the "Dunbar number," which suggests humans have a cognitive limit of approximately 150 meaningful relationships. His work outlines the substantial time investment required to form deep friendships.

Katy is a behavioral scientist at the University of Pennsylvania's Wharton School. She studies habit formation and willpower depletion, developing strategies like "temptation bundling." Her research explains why extreme health diets often fail, offering practical methods for making sustainable habit changes.