No single interpretation of the texts emerged, and several schools of Vedanta developed, differentiated by their conceptions of the nature of the relationship and the degree of identity between the eternal core of the individual self (atman) and the absolute (brahman).
These range from the nondualism (Advaita) of the 8th-century philosopher Shankara to the theism (Vishishtadvaita; literally “Qualified Nondualism”) of the 11th–12th-century thinker Ramanuja and the dualism (Dvaita) of the 13th-century thinker Madhva.
To understand the ancient world, it may be better to visit the holy places of India where the ancient traditions are still unbroken, rather than try to interpret ancient ruins through bricks and pottery shards, which scholars today usually do so according to their own modern mindsets, not recognizing the all-pervasive regard for the sacred that was the basis of ancient life and culture.
Most notably, ancient India presents us with by far the largest literature that has survived from the ancient world.
The Vedic literature of India, by all accounts dating from well before the time of the Buddha (500 BCE) and by traditional accounts extending back well over five thousand years (3100 BCE), covers several thousand pages.
This is with the four – the bedrock of Indian philosophy and Yoga – represent only the last layer or a late summation.
All major Vedantic teachers, like Shankara, Rāmānuja, and Mādhvāchārya, have composed often extensive commentaries not only on the Upanishads and Brahma Sutras, but also on the Gita.
All the Vedanta schools unanimously reject both the heterodox (nastika) philosophies of Buddhism and Jainism and the conclusions of the other orthodox (astika) schools (Nyaya, Vaisheshika, Samkhya, Yoga, and, to some extent, the Purva-Mimamsa).
In fact, Vedic words have many layers of meaning, of which the surface appearance can be misleading, particularly to the modern mind not used to such a multidimensional language. They reflect a pattern of cosmic sound that underlies all the laws of the universe and has its counterparts on all levels of both individual and cosmic manifestation.
This is also a phenomenon that we find throughout the ancient world. For this reason, the Veda was called the speak of secret meanings to their mantras that were veiled to protect the teaching from its application by the spiritually immature.
Spiritual and occult arts such as abounded in the ancient world – including Yoga, Vedic astrology, Ayurvedic medicine and the use of rituals (Yajnas) to improve all aspects of our lives – remain commonly used and are honored by the culture of India as a whole.
Indeed we could say that India is a living museum of the ancient world and its lost civilizations.