This book explores the metaphysical underpinnings of theories of human nature, personhood, and the self. The coverage of the work is broad in scope, moving from the Pre-Socratics to Postmodernism, critically assessing what transpired during the intervening 2500 year period, with a special focus on the contributions of the Aristotelian/Thomistic tradition of inquiry. The work is designed to meet the needs of a wide range of readers, from beginners to more advanced students.