In the West, the earliest use of the term "scapegoat" can be found in early Judaic ritual described in the Bible's Book of Leviticus. The passage goes something like this:
"On the Day of Atonement a live goat was chosen by lot. The high priest, robed in linen garments, laid both his hands on the goat's head, and confessed over it the iniquities of the children of Israel. The sins of the people thus symbolically transferred to the beast, it was taken out into the wilderness and let go. The people felt purged, and for the time being, guiltless."
The term scapegoat, however, has evolved to refer to individuals or peoples who are symbolically or concretely made to bear responsibility for the faults or problems of others. For individuals, scapegoating is a psychological defense mechanism of denial through projecting responsibility and blame on others. It allows the perpetrator to eliminate negative feelings about him or herself and provides a sense of gratification. Furthermore, it justifies the self-righteous discharge of aggression. For the perpetrator, it can provide a firm separation between good and bad. Others describe scapegoaters as insecure, motivated to raise their own status, particularly relative to the target. Having firmly convinced oneself that the other is responsible, it seems only logical to displace punishment as well.
It is unlikely, however, that this psychological explanation directly translates to the sociological level. At the group level, scapegoating does not reflect mass psychosis. At the same time, it is true that psychological issues may be involved for some group members and some may suffer from psychological problems. The aggregating of individuals to produce scapegoating at the societal level appears to be a complicated process involving a number of personality types and psychological processes. To put it simply, scapegoating involves the creation of a stark "us" vs. "them" dichotomy.
Regardless of whether individual or group scapegoating, it typically is based on real social, political, ideological, cultural, or economic power struggles.  Scapegoats are frequently less powerful and more marginalized. This makes them easier targets. However, they need not be. Many of them are in fact privileged, at least in relative terms. The Jews throughout Europe, Chinese in Southeast Asia, or Koreans in inner city Los Angeles are but three examples of the latter. In each case, assertions of unfair advantage provide an explanation for the inferior economic position of others. This sentiment is often beneficial for political leaders who can deflect blame from their own shortcomings. For example, there is evidence that Indonesian government leaders and the military fueled anti-Chinese sentiment after the economic collapse in 1998.
Scapegoating often becomes an important part of conflict. Once scapegoating is perceived to be successful in generating positive feelings in perpetrators, there is likely to be reluctance to give it up. The scapegoated provide a ready explanation for troubles. Therefore, there is relatively little incentive for the perpetrator to give it up. For the scapegoated, they are left with few good options: to flee, to assimilate, or to fight back.
By Eric Brahm
 Gordon W. Allport, Nature of Prejudice, Cambridge, MA: Addison-Wesley, 1954, p. 244.
 Richard Landes, "Scapegoating," Encyclopedia of Social History, Peter N. Stearn, ed., (New York: Garland Pub. Inc., 1994).
 S. Scheidlinger. On Scapegoating. International Journal of Group Psychotherapy. 32, 1982. p131-142.
 C. Allen Carter. Kenneth Burke and the Scapegoat Process. (Norman: University of Oklahoma Press, 1996).
 Michael Billig, Fascists: A Social Psychological View of the National Front, (New York: Harcourt Brace Jovanovich, 1978), pp. 313-316.
 Political Research Associates. "The Scapegoat" http://www.publiceye.org/tooclose/scapegoating-02.html#P20-4038
 Allport, pp. 29-67.
 Lise Noel, Intolerance, A General Survey, (Montreal: McGill-Queen's University Press, 1994), pp. 149-164.; Elisabeth Young-Bruehl, The Anatomy of Prejudices, (Cambridge, MA: Harvard University Press, 1996), pp. 353-365.
 Human Rights Watch. 1998. "Indonesia Alert"http://www.hrw.org/press98/feb/indo- al1.htm