This book proposes a bold idea. Living beings are distinguishing distinctions. Single cells and multicellular organisms maintain themselves distinct by drawing distinctions. This iswhatorganisms are andwhatthey do. From this starting point, key issues examined range across ontology, epistemology, phenomenology, logic, and ethics. Topics discussed include the origin of life, the nature and purpose of biology, the relation between life and logic, the nature and limits of formal logic, the nature of subjects, the subject-object relation, subject-subject relationships and the deep roots of ethics. The book provides a radical new foundation to think about philosophy and biology and appeals to researchers and students in these fields. It powerfully debunks mechanical thinking about living beings and shows the vast reservoir of insights into aliveness available in the arts and humanities.