In the Later Vedic period religion, thoughtful men expressed doubts in the efficiency of sacrifices and simple worship of the forces of nature.
The ‘Brihadaranyaka Upanishada’ expounded the doctrine of transmigration of the soul. Philosophical thought made steady progress. Many people took to ascetic life, by withdrawing from community. They began to live as wandering hermits. They were called Aranyakas or forest hermits and Sannyasins or ascetics. Living a life of detachment from worldly life they could easily understand the futility of Yajna and sacrifices.
They were able to find that neither Yajna nor worship could liberate the soul of a man from the law of the Karma.
Pessimism colored their minds and out of this arose the concept of Dhyana or meditation and the attempt to liberate man from his Karmafala. Ascetic life, penance and meditation were declared more useful than Yajna and worship.
The Upanishads preached the doctrine of Brahman or Supreme Being or the Creator. After death man returns to the bosom of the Creator – the Brahman; jivatma returns to its original root Paramatma. That man must not forget that he is a part of that Great whole and should act accordingly.
Another view regarding the origin of asceticism should also be noted here. The tribal kingdoms of the Early Vedic age were giving way to large kingdoms, there was a great dislocation in society. There was huge competitions for land. Village lands were split into private holdings. The community ownership of land began to decline. As a result weak and unambitious persons were rejected from land and property. There was also competition in trade sector due to development of river traffic along the Ganges. There was a profound insecurity. Sensitive persons escaped from this horrid life by with-drawing from society and becoming ascetics.
There may be difference of opinion about the origin of asceticism. However, many of the ascetics were truly philosophical and thoughtful men. They preached new philosophy about the salvation of the soul which we can find in the Upanishads and Sutras. As a result there developed six new philosophical schools of thought such as Nyaya, Vaisheshika, Sankhya, Yoga, Mimansa and Vedanta. Scholars point out that facing the challenge from the ascetics, Sannyasa or asceticism was included as a stage of the four Ashramas that governed the life of a male.
However, the people of Later Vedic era also believed in sacrifices and rituals. The common people worshipped Gods to seek their blessings. Since, most of the people were dependent upon agriculture, they continued worshiping the various forces of nature.