evidence: Hindus believe a person is born into one of four castes based on karma and "purity"—how he or she lived their past lives. Those born as Brahmans are priests and teachers; Kshatriyas are rulers and soldiers; Vaisyas are merchants and traders; and Sudras are laborers. Within the four castes, there are thousands of sub-castes, defined by profession, region, dialect, and other factors.