This book traces the history of life-concepts, with a focus on the vegetable souls of Aristotle, investigating how they were interpreted and eventually replaced by evolutionary biology. Philosophers have long struggled with the relationship between physics, physiology, and psychology, asking questions of organization, purpose, and agency. For two millennia, the vegetable soul, nutrition, and reproduction were commonly used to understand basic life and connect it to higher animal and vegetable life. Cartesian dualism and mechanism destroyed this bridge and left biology without an organizing principle until Darwin. Modern biology parallels Aristotelian vegetable life-concepts, but remains incompatible with the animal, rational, subjective, and spiritual life-concepts that developed through the centuries. Recent discoveries call for a second look at Aristotles ideas though not their medieval descendants. Life remains an active, chemical process whose cause, identity, and purpose is self-perpetuation.

Lucas John Mix is an associate of the Department of Organismic and Evolutionary Biology at Harvard University, USA. He works at the intersection of biology, history, philosophy, and theology and has worked with NASA Astrobiology programs for the last 20 years on understanding the meaning and extent of life.

1. Vegetable Souls?.- 2. Greek Life Psyche and Early Life-Concepts.- 3. Strangely Moved Appetitive Souls in Plato.- 4. Three Causes in One Biological Explanation in Aristotle.- 5. Life in Action Nutritive Souls in Aristotle.-6. Plants versus Animals in Hellenistic Thought.- 7. The Breath of Life Nephesh in Hebrew Scriptures.- 8. Life after Life Spiritual Life in Christianity.- 9. Invisible Seeds Life-Concepts in Augustine.- 10. Aristotle Returns A Second Medieval Synthesis.- 11. Life Divided Vegetable Life in Aquinas.- 12. Mechanism Displaces the Soul.- 13. Divided Hopes Physics versus Metaphysics.- 14. Ghosts in the Machine Vitalism.- 15. The Same and Different Early Theories of Evolution.-16. Vegetable Significance Evolution by Natural Selection.- 17. Vegetables versus Modern Plants.- 18. Counting Lives- Regulators and Replicators.- 19. What Can Be Revived (and What Cannot).