Stratification systems essentially separate people into haves and have-nots. Attempting to analyse why stratification emerges, most social thinkers barring a few geniuses have concluded that some social inequality is inevitable.

The classical conservative position suggests that inequality is part of the law of nature. It holds that people are basically selfish and greedy. Social institutions must curb this greed and selfishness or the society will not function smoothly. The curbing is done by institutions; however, institutions also promote inequality. Inequality is the price societies must pay to ensure peace and order. Later, the social Darwinists proposed that because the resources of society were scarce and people had to compete for them, only the strongest, the most intelligent or those most willing to work would acquire most of the good things in life. This situation would result in inequality, but at the same time it would ensure that only the worthiest people in a society rose to positions of power and privilege. Ultimately, this would benefit society, for such people would provide enlightened leadership.

In the classical liberal view, humans are considered essentially good rather than selfish and greedy. It is society and its institutions that corrupt people, because each individual or group must struggle to get a share of the scarce goods and services that the society offers. The struggle becomes divisive and ends with the dominance of one group over others. The dominant group is able to exploit the others and, once in a position of power, to impose its will on the remainder of society. Inequality and stratification are then unavoidable.

Structural-Functionalist Perspective

The intellectual descendants of the conservative viewpoint are represented by the structural-functionalist school of thought in sociology. Functionalists stress the needs of the society rather than those of the individual, reasoning that the needs of individuals can be satisfied only within the society. The existence of every society depends on the regular performance of specific tasks that are difficult and require special intelligence, talent and training. Societies must institute systems of rewards with which to lure the most talented, the most intelligent and the best-trained individuals to perform these tasks. The positions most essential to the welfare of a society, and positions for which there are a few qualified personnel, must be the ones that are most highly rewarded (Davis and Moore 1945). It may be argued that collecting garbage is almost as vital to the health of a society as practising medicine, because uncollected garbage is a threat to public health, but collecting garbage a little training or talent; therefore, many individuals are capable of performing this function. Practising medicine, however, requires a long period of study and training. Not all individuals are capable of undergoing the discipline of such training; therefore, there are fewer potential doctors than potential garbage collectors, and consequently doctors should be much better rewarded.

In addition, functional theorists stress the need for order, stability and balance in society. Even though it produces some social inequality, they maintain, a system of stratification has a stabilizing influence on society. Finally, functionalists conclude that inequality is built into the social system because not all types of work are equally necessary for, and thus valued by, the society.