Talcott Parsons believe that order, stability and cooperation in society are based on value consensus that is a general agreement by members of society concerning what is good and worthwhile. Stratification system derives from common values it follows from the existence of values that individuals will be evaluated and therefore placed in some form of rank order. Stratification is the ranking of units in a social system in accordance with the common value system. Those who perform successfully in terms of society's values will be ranked highly and they will be likely to receive a variety of rewards and will be accorded high prestige since they exemplify and personify common values. According to Kingsley Davis and Moore stratification exists in every known human society.
All social system shares certain functional prerequisites which must be met if the system is to survive and operate efficiently. One such prerequisite is role allocation and performance. This means that all roles must be filled. They will be filled by those best able to perform them. The necessary training for them is undertaken and that the roles are performed conscientiously. Davis and Moore argue that all societies need some mechanism for insuring effective role allocation and performance. This mechanism is social stratification which they see as a system which attaches unequal rewards and privileges to the positions in society. They concluded that social stratification is a device by which societies insure that the most important positions are conscientiously filled by the most qualified persons.