The Abhidhamma expounds a revolutionary system of philosophical psychology rooted in the twin Buddhist insights of selflessness and dependent origination. In keeping with the liberative thrust of early Buddhism, this system organizes the entire spectrum of human consciousness around the two poles of Buddhist doctrine—bondage and liberation—the starting point and the final goal. It thereby maps out, with remarkable rigor and precision, the inner landscape of the mind to be crossed through the practical work of Buddhist meditation. In this book of groundbreaking essays, Venerable Nyanaponika Thera, one of our age's foremost exponents of Theravada Buddhism, penetrates the Abhidhamma to make its principles intelligible to the thoughtful reader of today. Innovative and rich in insights, this book does not merely open up new avenues in the academic study of early Buddhism. By treating the Abhidhamma as a fountainhead of inspiration for philosophical and psychological inquiry, it demonstrates the continuing relevance of Buddhist thought to our most astute contemporary efforts to understand the elusive yet so intimate nature of the mind.