In this opening volume, The Foundations of Natural Temperament and the Four Humors, of Ibn S¿n¿'s monumental Canon of Medicine, the reader enters the living architecture of classical science-where health and disease are governed by balance, not chance. Here, the philosopher-physician unfolds the universal principles of life: the elemental roots of nature, the temperaments that shape bodies and dispositions, and the four humors-blood, phlegm, yellow bile, and black bile-through which vitality circulates and decline begins.With clarity and precision, Ibn S¿n¿ reveals how moderation sustains existence and how its disturbance gives rise to illness. This first book thus forms the foundation of the entire medical art, offering both the logic and the ethics of care that unite body, soul, and cosmos.The Ancient Wisdom Collection continues with the subsequent volumes of the Canon, each devoted to a distinct realm of knowledge-from the organs and their faculties, to the causes and cures of disease, and the composition of remedies-restoring to view one of humanity's most enduring systems of thought.