De Anima

De Anima, written by Aristotle in the 4th century BCE, is a foundational text on the nature of living beings and the concept of the soul. Aristotle categorizes souls based on their functions: plants possess the basic capacities for nourishment and reproduction, lower animals have sensory perception and movement, while humans uniquely possess intellect. This treatise challenges modern interpretations of the soul, positing that it is the essence of an organism, inseparable from the body, and essential for understanding life itself.