One redeeming feature in this age was the continuity of the process of
Hindu-Muslim synthesis and amicable contact between the members of the two
communities. Consequently the spirit of synthesis and mutual harmony led to the
Major sources of it are Upnishads, Later Vedic Period, developing and
evolving over 2000 years. There are two types of Schools first is Orthodox (astika)
or non-orthodox (nastika), if Veda is an infallible source of knowledge or not.