Men could worship their gods, and indeed could wield a degree of control, through religious ceremonies that aimed to elicit benefits from them.
The Upanisads took a more subtle turn, concentrating on a deeper understanding of the nature of man himself. The "inner self," the atman, was distinguished from its physical embodiment and was taken to proceed through a series of rebirths according to a causal law of karma—whereby moral merit or demerit dictated the nature of the next rebirth. Ultimately it would hopefully achieve release from rebirths and acquire its final state of bliss (moksa).
The period from the fourth to the second century BCE was one of quite subtle developments, with new and deeper ideas of the causal operation of the law of karma, of the nature of human existence, and of the nature of and route to the soteriological end for man. The Hindu Bhagavad Gītā was composed—a part of the great epic the Mahabharata (the actual period of composition is still much disputed)—and two nonorthodox systems of ideas were introduced: Jainism and Buddhism. Interestingly, both Jainism and Buddhism have no place for deities in their systems, human existence and progression to the ultimate state of release from rebirth being said to depend on the efforts of the individual.
