TEMPERAMENT: Wide Margin Study Edition

TEMPERAMENT presents the culminating work of David W. Keirsey (1921–2013), whose contributions helped shape the modern understanding of personality and human behavior. With the publication of Please Understand Me (1978) and Please Understand Me II (1998), Keirsey became the first American psychologist to publish a book on temperament and personality types for a broad public audience. Within these works, he introduced the first personality assessment to be made widely accessible beyond professionally administered settings. Over time, Keirsey Assessments have been used by more than 750 million people worldwide. His books not only helped popularize structured approaches to understanding personality, but also challenged the prevailing assumption that such tools should remain restricted to trained experts—advancing the view that individuals are capable of engaging and interpreting these frameworks for themselves. At the time, personality assessments were largely restricted to certified practitioners—psychologists, psychiatrists, and formal academic programs. With Dr. Keirsey's research released to the public, that boundary was lifted. In doing so, Keirsey shifted paradigms, establishing the conditions for what would become a far more accessible and widely adopted field. In today's era, personality assessments are nearly universal—appearing in digital platforms, organizational tools, and self-directed materials—reflecting a level of accessibility that was never imagined. Within this context, industry insiders have at times referred to Keirsey as the “Godfather”—the “OG,” if you will—of this movement toward accessibility, suggesting that his work helped give rise to an industry whose scale and reach he himself did not set out to create. Today, the global personality assessment industry has expanded into a multi-billion-dollar sector—as organizations seek systematic ways to understand human behavior for team dynamics, leadership, strategy, and customer engagement. The framework has since been applied across a wide range of institutional contexts, including every White House administration since the 1980s, all branches of the U.S. military, intelligence organizations, major corporations, universities, consulting firms, and faith-based institutions and social enterprises worldwide. It has been adopted by 75% of the Fortune 500, including 99 of the Fortune 100, as well as by leading academic institutions and professional organizations. Today, more than 100,000 people engage with Keirsey tools and materials on a daily basis. This volume draws from the final phase of Dr. Keirsey’s work. In his later years, he continued to refine his ideas, producing an extensive body of manuscripts, notes, and conceptual revisions. These materials—preserved and entrusted to a broader community of researchers and practitioners—reflect his view that temperament theory was not a finished system, but an evolving inquiry. For Keirsey, intellectual progress was an ongoing process of observation, revision, and discovery; as his colleagues often remarked, he was always “revising his revisions.” TEMPERAMENT presents an organized expression of those final reflections: the result of a lifetime devoted to understanding the enduring patterns that shape human nature. This Wide Margin Study Edition of TEMPERAMENT was originally designed for those undergoing certification training with Keirsey, but is now being released to serious students of human behavior who wish to engage the material at that same level of depth. This volume is best approached as a text for careful study. The wide margins are intentional—for you to devour those spaces to reflect, learn, discern, interpret, and integrate what you're learning into your life. TEMPERAMENT is an entry into a continuing conversation about how and why human beings differ, and how those differences shape the world we create together.