From "Some Principles of Stratification" by Kingsley Davis and Wilbert

From "Some Principles of Stratification" by Kingsley Davis and Wilbert Moore
Davis and Moore offer a classical "functional" account of stratification. In particular, stratification is viewed as functional for the overall good of society. This perspective emphasizes the functional importance of positions, not the individuals who fill them; filling them ensures that all of the jobs necessary for the sustainability of society will be performed. These roles, however, contribute to the functioning of society to different degrees and the rewards attached to them are a product of how important particular roles are. Individuals who perform these roles are seen as motivated to perform them because there is a natural tendency for the abilities and talents of the individual to find the appropriate role in a social structure.
-According to the functional theory, stratification is inevitable.