The functionalists, Parsons and Kingsley Davis approach the problem of inequality from the perspective of society at large seeing it as a necessary feature of any properly functioning human society. According to Kingsley Davis social inequality is an unconsciously evolved device by which societies insure that the most important positions are conscientiously filled by the most qualified persons. Stratification arises basically out of the needs of societies not out of the needs or desires of individuals. The systems of stratification arise in response to two specific needs common to every human society.
First there is the need to instil in the abler members the motivation to occupy important and difficult positions which require greater than average ability .Second society must motivate such men once they are in these positions to perform the duties attached to them. Hence it must provide them with greater rewards. The two factors which are major determinants of the magnitude of the rewards attached to positions are their functional importance for the society and the relative scarcity of qualified personnel.
The system of stratification in any society is essentially an expression of the value system of that society. The rewards which men and positions enjoy are a function of the degree to which their qualities, performance and possessions measure up to the standards set by their society. Since men differ in these aspects, inequality is inevitable.