A Founding Father whose long and intellectually active life illustrates the book's principles of mental sharpness and social engagement.

The author's late father, a pediatrician whose practical wisdom serves as a personal anchor and model for the book's core wellness rules.

The ancient Greek philosopher who provides a classical foundation for the argument that social connection is essential to a fulfilling life.

A Harvard professor whose research on relationships and longevity provides empirical support for the book's focus on social connections.

An evolutionary psychologist whose work on social networks gives a scientific perspective on the mechanics of friendship.

A behavioral scientist known for her research on habit formation, which offers strategies for adopting and maintaining healthy habits.