Below are the seven propositions that make up the structural-functional theory of social stratification (Davis and Moore) as summarized by Melvin M. Tumin.* These statements argue that social stratification (inequality) is functional and it is necessary for maintaining a society's state of equilibrium (stability).

1. Certain positions in any society are more functionally important than others and require special skills for their performance.
2. Only a limited number of individuals in any society have the talents which can be trained into the skills appropriate to these positions (i.e., the more functionally important positions).
3. The conversion of talents into skills involves a training period during which sacrifices of one kind or another are made by those undergoing the training.
4. In order to induce the talented persons to undergo these sacrifices and acquire the training, their future positions must carry an inducement value in the form of differential, i.e., privileged and disproportionate access to the scarce and desired rewards which the society has to offer.
5. These scarce and desired goods consist of rights and perquisites attached to, or built into, the positions and can be classified into those things which contribute to A) sustenance and comfort; B) humor and diversion; Q self-respect and ego expansion.
6. This differential access to the basic rewards of the society has as a consequence the differentiation of the prestige and esteem which various strata acquire. This may be said, along with the rights and perquisites, to constitute institutionalized social inequality, i.e., stratification.
7. Therefore, social inequality among different strata in the amounts of scarce and desired goods, and the amounts of prestige and esteem which they receive, is both positively functional and inevitable in any society.

To read the original Davis and Moore article click here. *(American Sociological Review, Vol. 18 (August, 1953).