While elucidating their evolution in the Indian moral thinking, critically discuss the concepts of Rta and Dharma.

During the early periods of Vedic era, the term Rta or Rtam was used to designate the cosmic moral principle according to which all things in universe operate. Thus, Rta is a principle of natural order which regulates and coordinates the operation of the universe and everything within it.
The Rig-vedic people realized that there must be some cosmic order which like a wheel circumscribes the universe regulates it and keeps it in place. The controller of this cosmic order is Varuna. Aryans offered the pray to Varuna, the supreme ruler of Rta and believed that they would be punished by Varuna of they don’t fulfil their duty towards friends, guests, brothers and other members of their families. This is how the concept of Rta was used for maintenance of order in the society. The basic idea was that every human being was creation of god and had to be treated on equal footing.
In later era, the concept of Rta was superseded by Dharma in the history of Indian moral thinking. There are various explanations to Dharma. Brahmanas say that Dharma comprised the performance of ritual sacrifices; while Upanishads such as Chhandogya says that Dharma is good conduct. As per this, a virtuous man should develop the virtues of penance, charity, straightforwardness, non-violence and truth.
The Dharma concept was later overlapped with Karma and other such concepts. This was followed by composition of Dharamashashtras, which would then try to codify what is Dharma. For example, stealing gold, drinking, killing a Brahmin, desecrating the teacher’s bed etc. were defined as great sins. Thus, we can say that concept of Dharma was not static. Its content changed in the changing contexts of time, place, social environment etc.