Charaka Samhita, composed by Sage Charaka, considered to be the most ancient and authoritative writing on ayurveda, also elaborates on the logic and philosophy on which this system of medicine is based. According to Charaka, science is dependent upon yukti, a quality of the intellect. Much of the treatise of Charaka Samhita is in the form of a symposium wherein various topics are discussed by groups of ayurvedic scholars. The samhita mentions about the gradual development of the fetus within the womb in minute detail, that accurately equals the modern medical version. Written in Sanskrit, the samhita contains about 8,400 metrical verses.
Charaka followed the Atreya School of Physicians, which dealt with treatments involving internal and external application of medicine. The samhita focuses on healing the body, mind and soul of a patient in the minimum invasive manner. Laying great emphasis on the diagnostic part of the treatment, Charaka identified eight stages of a disease from its inception to the culmination. Charaka also placed great importance on the timing and manner of collection of medicinal plants.