In spite of the efforts of many reformers we'll be meeting in future episodes of Crash Course, the caste system is the foundation for another big concept in Hinduism, Part Three, Dharma. Dharma is basically one's role in life and society, and it is defined primarily by birth and by caste. This whole idea is explained nicely in this passage from the Bhagavad Gita, where Krishna is talking to the warrior Arjuna. "...having regard to your own duty also, you ought not to falter. For there is nothing better for a Kshatriya than a righteous battle." The Bhagavad Gita is a section of a much larger epic poem called the Mahabharata, which basically tells the complicated and long story of a war between two kingdoms. And we can really see how important Dharma is in this passage, because Krishna is basically telling Arjuna that because he is a warrior, a Kshatriya, he must fight.