The emergence of different schools of Sanskrit philosophy like Nyaya, Vaisheshika, Sankhya, Yoga, Vedanta and Mimamsa was another landmark in the history of Indian medicine. The principles expounded in these philosophies helped Ayurveda in developing its theory of humoral pathology. At the core of Ayurveda lies the theory that the human body is composed of three humors - Pitta, Vata and Kapha. The body which has these three humors in a state of equilibrium enjoys perfect health and their disequilibrium causes ill health .

Interestingly, though the theory apparently develop under the influence of the philosophies, what is quoted as the earliest reference to the theory appears in the Rig Veda:

Tridhatu Sarma vahanam Subhasathi

The Atharva Veda also has terms like Vatikrita which means a disease caused by the derangement of the humor Vata, and Vatagulman. However no further development of the idea can be seen anywhere in the Vedic scriptures.

More than a thousand years after the period of Atharva Veda came the age of the samhitas or compendiums. The term Ayurveda first appears in the samhitas, the earliest record works on Indian medicine. In Sanskrit, ayu means life and veda, science or wisdom.

It was during this age that marked the end of the oral tradition that medical treatment freed itself from the mantras and spells of the Vedic age. An unprecedented factual and materialistic approach to human health was adopted.

For the purpose of specialization of the science, it was divided into eight limbs –the Ashtanga. The ancient savants also incorporated into Ayurveda the theories of Nvava, Vaisheshika and Sankhya epistemology defining the origins of the material world science Ayurveda as a medical system also deals with gross matter. Hence, the concept of the Pancha Maha Bhutas (the Five Great Elements), a material concept interwoven with the theory of the thridoshas, forms the foundation of the science.

The age of compilation witnessed immense production of classical medical literature. Shushruta Samhita, Kashyapa Samhita, Agnivesa Samhita, Bhela Samhita, Jatukarna Samhita, Kharanada Samhita, Usana Samhita, Agastya Samhita and so on were the important works of the period.

The Agnivesa Samhita, later redacted by Charaka, and the Sushruta Samhita, revised by Nagarjuna considered to be masterpieces - are the only works that have survived. The others might have either been destroyed or become fragmented .