These different explorations of 'identity' demonstrate how difficult a concept it is to pin down. Since identity is a virtual thing, it is impossible to define it empirically. Discussions of identity use the term with different meanings, from fundamental and abiding sameness, to fluidity, contingency, negotiated and so on. Brubaker and Cooper note a tendency in many scholars to confuse identity as a category of practice and as a category of analysis (Brubaker & Cooper 2000, p. 5). Indeed, many scholars demonstrate a tendency to follow their own preconceptions of identity, following more or less the frameworks listed above, rather than taking into account the mechanisms by which the concept is crystallised as reality. In this environment, some analysts, such as Brubaker and Cooper, have suggested doing away with the concept completely (Brubaker & Cooper 2000, p. 1). Others, by contrast, have sought to introduce alternative concepts in an attempt to capture the dynamic and fluid qualities of human social self-expression. Hall (1992, 1996), for example, suggests treating identity as a process, to take into account the reality of diverse and ever-changing social experience. Some scholars have introduced the idea of identification, whereby identity is perceived as made up of different components that are 'identified' and interpreted by individuals. The construction of an individual sense of self is achieved by personal choices regarding who and what to associate with. Such approaches are liberating in their recognition of the role of the individual in social interaction and the construction of identity.
Many scholars confuse identity as a category of practice and what other category?
category of analysis

In their attempt to ensure white supremacy decades after emancipation, in the early 20th century, most southern states created laws based on the one-drop rule, defining as black, persons with any known African ancestry. This was a stricter interpretation than what had prevailed in the 19th century; it ignored the many mixed families in the state and went against commonly accepted social rules of judging a person by appearance and association. Some courts called it "the traceable amount rule." Anthropologists called it an example of a hypodescent rule, meaning that racially mixed persons were assigned the status of the socially subordinate group.
What is the one-drop rule?
black, persons with any known African ancestry.

In early 1991, non-Arabs of the Zaghawa tribe of Sudan attested that they were victims of an intensifying Arab apartheid campaign, segregating Arabs and non-Arabs (specifically people of sub-Saharan African descent). Sudanese Arabs, who controlled the government, were widely referred to as practicing apartheid against Sudan's non-Arab citizens. The government was accused of "deftly manipulat(ing) Arab solidarity" to carry out policies of apartheid and ethnic cleansing.
When did the Arab apartheid intensify?
early 1991