Kula and Yajna, Rita and Tapas as the Central  Idea
The Aryans who founded Indian  culture had certain basic social institutions like Kula (family) and  Jana (tribe). The Aryans brought some important elements with them  namely the horse (an imp instrument of warfare), powerful social  institutions and a collective will to action.
Among social institutions was the  Patriarchate. The father was the head of the family, its members and  properties. The departed ancestors were bound in an intimate relation  with the family. Grand-fathers, sons and so on were one in spirit,  traditions and property.
The family or Kula led to the  concept of Gotra or a group of families from common descent. A  federation of gotras made the Jana or tribe. Therefore, the father  provided the bonding to a family passing down traditions from one  generation to another. Thus, the family became central to every  person’s existence. It molded members from infancy, inspired by  love, sacrifice, pride of parental action.
Unlike in the West, where an  individual is given more importance than society, family functions as  a support mechanism in India and, hence is an important part of our  culture. The above also explains why the father is the head of the  Indian family. Another important characteristic of Vedic culture was  lifelong unity of husband and wife. This explains why divorce  rate amongst Indian couples is lower as compared to the West. In  fact, a recent survey carried out in England confirms that divorce  rate amongst Indians is the lowest there. 
Another socio-religious institution  was Yagna, the ritual of sacrifice that brought men, their  ancestors and gods into an intimate relationship. Behind yagna was  the spirit of sacrifice. Every human is to offer his precious  possessions (greed, fear, anger, hatred, and ego) to the Cosmic Law,  releasing creative energy, that can be used for productive purposes.  If performed in true spirit it was a means of uniting men with gods  not only to meet desired ends, but to secure lasting creation.
The ordinances according to the  yagna were prescribed by Rita, the Eternal Law, which  upheld the Cosmic Order. Rita was all pervading, omnipresent from  which creation sprang and by which life was regulated. Everyone, Gods  included had to conform to its ordinances. It was independent of gods  and men. The gods were its guardians, they were mighty because of it.  Rita was not merely the source of strength but also of beauty. Ushas  the goddess of dawn was beautiful because she was true to Rita. One  could taste immortality only on the lofty heights of Rita.
Satya was that aspect of Rita  that gave conduct the power to yield desired results. It produced  results only when there was a complete accord between thought, word  and deed of an individual. When men prayed to God, their blessings  had to be satya ie true to expectations.
Tapas yagna could be fruitful  only if it is performed with the spirit of sacrifice or Tapas. This  meant offering of life through prayer to the gods in order to conform  to Rita. Tapas is self- discipline for attaining purity of mind and  body. Scorning human comforts, it gives self control to man. It  transforms weaknesses into strength and inspiration. Sublimation of  the ego releases energy which can be used positively.
Therefore, the central idea  underlying Indian culture is Rita, the cosmic order that is one and  indivisible, operating in spiritual and moral fields. It governs and  regulates life and its evolution. Its  Divinity is represented by   God. The manifestations of Rita have many aspects, its fundamental  values being Satya, Yajna, and Tapas.
It is a tribute to the Rishis of  four thousand years ago who saw this Central Idea in all its  universality and through it sought to coordinate all values of life  and shaped, vitalized institutions, norms to fulfill it.
The Vedic Rishi and his Ashram 
Rita was translated into life  through social institutions, norms of conduct and discipline which  lifted the daily conduct into an act of Yajna. The ashram was the key  institution where the Vedas were learned and practiced. The Rishi  lived with his pupils. He taught them the message of the gods through  mantras, how to worship them through sacrifice and inspire men to  follow the ordinances of Rita. Each ashram was a closely knit family.  It rested on the collective support of the community who looked up to  it as a source of inspiration for life well lived.
In Vedic India, the Rishi was a not  a priest. He was a teacher whose life was dedicated to the Gods and  Rita. The first step in translating Rita in life was through training  in self-disciplined behavior under an Acharya (a rishi of repute). He  was a spiritual guide to the student. At an early stage of  consecration (diksha) a young person had to learn how to conform to  the Rita through vratas or pledges of disciplined behavior. Diksha  stood for a life of discipline dedicated to prayers, learning and  teaching. When an Arya was consecrated he became a Brahmachari.
In succeeding ages our culture  maintained its vitality because it depended on this class of  dedicated, self-disciplined students for its creative vigor. A  culture flourishes only when its educational system imparts a sense  of mission to the youth and trains them to lead a disciplined life.  If the new generation is self-indulged, then that means the system  has failed to capture the values of the culture. Consequently, decay  follows bringing with it social, moral, and cultural disintegration.
The above para explains two  things. First, why has the Indian civilization survived inspite  of many foreign invasions? The rishis and students passed on the  knowledge of Rita from generation to generation. Since they were  spread throughout  the country, even if an invader destroyed 25  ashrams there were thousand others that survived. 
Secondly, what is the reason for the  current decay in our society? It is to do with the failure of the  current educational system. I am no expert but feel that mass based  education has failed to deliver. It is bookish, impersonal,  continuously harps on acquisition of material objects, does not teach  us how to handle life and ignores personality development. Instead of  reading about Indian books, we study European literature in  Shakespeare and Macbeth. This has made a substantial part of the  urban population ignorant about Indian culture. 
A recent issue of The Outlook  pointed out that a number of urban Indians, between 20-30 years, use  religion / spirituality to cope with Stress.
Now days some of us turn spiritual  after the age of fifty. Do we get the maximum benefit out of doing  so? The answer is No. After having lived most of our lives in  ignorance and suffered we turn spiritual. Having realized the  benefits of turning spiritual in my thirties, sometimes wonder how  much I have lost because we were not taught spirituality in school. 
Brahmacharya was during training  period only. Marriage and children were part of the tradition. The  student of a Rishi, dedicated to Rita was looked upon as a leader and  was to play the role of a dominant minority in society providing  insight, judgment to translate values into life. 
The highest function which the Rishi  had to perform was to compose, preserve and transmit the sacred hyms.  The divinity of the Vedas became one of the fundamental values of  Vedic culture. It was a unifying factor and a source of perennial  inspiration. Note that chanting of the Vedas was not the  exclusive privilege of the Brahmins.
The Rishis extended their sphere of  influence throughout  India. In the process Aryan traditions mixed  with Dravidian and tribal traditions to become a composite culture.  Aryan culture started moving South/Westwards. One of the rishis,  Agastya is credited with being the father of Tamil grammar and  poetry. Namboodiri Brahmans of Kerala claim descent from Parashurama. 
There were a number of wars between  the Aryans themselves and with the Dravidians like the Battle of Ten  Kings. Such protracted wars appear to have ended the Vedic period.