differences between theoretical constructs and the practical reality. Modern perspective on definition Ronald Inden, the Indologist, agrees that there has been no universally accepted definition. For example, for some early European documenters it was thought to correspond with the endogamous varnas referred to in ancient Indian scripts, and its meaning corresponds in the sense of estates. To later Europeans of the Raj era it was endogamous jatis, rather than varnas, that represented caste, such as the 2378 jatis that colonial administrators classified by occupation in the early 20th century. Arvind Sharma, a professor of comparative religion, notes that caste has been used synonymously to refer to both varna and jati but that "serious Indologists now observe considerable caution in this respect" because, while related, the concepts are considered to be distinct. In this he agrees with the Indologist Arthur Basham, who noted that the Portuguese colonists of India used casta to describe The sociologist Andre Beteille notes that, while varna mainly played the role of caste in classical Hindu literature, it is jati that plays that role in present times. Varna represents a closed collection of social orders whereas jati is entirely open-ended, thought of as a "natural kind whose members share a common substance." Any number of new jatis can be added depending on need, such as tribes, sects, denominations, religious or linguistic minorities and nationalities. Thus, "Caste" is not an accurate representation of jati in English. Better terms would be ethnicity, ethnic identity and ethnic group. Flexibility Sociologist Anne Waldrop observes that while outsiders view the term caste as a static phenomenon of stereotypical tradition-bound India, empirical facts suggest caste has been a radically changing feature. The term means different things to different Indians. In the context of politically active modern India, where job and school quotas are reserved for affirmative action based on castes, the term has become a sensitive and controversial subject. Sociologists such as M. N. Srinivas and Damle have debated the question of rigidity in caste and believe that there is considerable flexibility and mobility in the caste hierarchies. Origins Perspectives There are at least two perspectives for the origins of the caste system in ancient and medieval India, which focus on either ideological factors or on socio-economic factors. The first school focuses on the ideological factors which are claimed to drive the caste system and holds that caste is rooted in the four