Impaired consciousness is a topic lying at the intersection of science and philosophy. It encourages reflection on questions concerning human nature, the body, the soul, the mind and their relation, as well as the blurry limits between health, disease, life and death. This is the first study of impaired consciousness in the works of some highly influential Greek and Roman medical writers who lived in periods ranging from Classical Greece to the Roman Empire in the second century CE. Andrés Pelavski employs the notion and contrasts ancient and contemporary theoretical frameworks in order to challenge some established ideas about mental illness in antiquity. All the ancient texts are translated and the theoretical concepts clearly explained. This title is also available as open access on Cambridge Core.