Inequality appears to have always been an inherent feature in society and is no exclusive characteristic of a particular social pattern or period of history. The main forms of social inequality are those that result from disparities of wealth and income, those related to differential prestige or honour, and those derived from the distribution of power. These dimensions of inequality are related but not reducible to each other.
Social inequality can be based on natural differences of kind between people (sex, race, character traits, natural endowments) and on institutional variations (citizenship, religion, social position, etc); or on natural differences of rank (properties that are common to all but in varying amounts) in intelligence, age, strength, power, [etc]. It is the unequal treatment that results from these unequal characteristics that constitutes social inequality. It has a distributive aspect which refers to the ways in which different factors such as income, wealth, education, occupation, power, skill, etc, are distributed in the population and a relational aspect which refers to the ways in which individuals differentiated by these factors are related to each other within a system of groups and categories.
Throughout society, social inequality is still an extensive source of conflict. Although both types of industrial society - socialist and capitalist - have provided opportunities for social equality, and inequality has thus largely decreased during the last decades, it remains a fact that even in these affluent societies, people are still unequally placed. Nevertheless these inequalities seem small when compared to the far more obvious forms of social inequality in the Third World.
Inequality is justified and only justified when the man or woman who is the victim of inequality prefers the social, political or economic disadvantage of that position to the price that has to be paid for greater equality. Such a situation no longer needs to be hypothesized. It is the basis of at least some of the unrest that led to the break up of the former Soviet Union. A man, offered the prospect of three pairs of shoes -- all of which are identically badly made, ill-fitting and of the same drab design and colour -- is not necessarily consoled by the knowledge that everyone has three pairs of shoes of the same sort. He would probably prefer two pairs of his own choice -- even if it meant that other men has more shoes than he possessed. Similarly there is no such excuse as different but equal. Children who are born into deprivation grow up with an infinitely higher risk of being permanently disadvantaged than children born into affluence. It is as simple as that.
On this point Pope Leo XIII made apt and appropriate comment: "God has commanded that there be differences of classes in the human community and that these classes, by friendly cooperation, work out a fair and mutual adjustment of their interests." For it is quite clear that "as the symmetry of the human frame results from suitable arrangement of the various parts of the body, so in a body politic it is ordained by nature that...the classes should dwell in harmony and agreement, so as to maintain the balance of the body politic. Each needs the other: capital cannot do without labor, nor labor without capital. Their mutual agreement will result in the splendor of right order." Anyone, therefore, who ventures to deny that there are differences among social classes contradicts the very laws of nature. Indeed, whoever opposes peaceful and necessary cooperation among the social classes is attempting, beyond doubt, to disrupt and divide human society; he menaces and does serious injury to private interests and the public welfare. As Our predecessor, Pius XII, wisely said, "In a nation that is worthy of the name, inequalities among the social classes present few or no obstacles to their union in common brotherhood. We refer, of course, to those inequalities which result not from human caprice but from the nature of things -- inequalities having to do with intellectual and spiritual growth, with economic facts, with differences in individual circumstances, within, of course, the limits prescribed by justice and mutual charity.'' The various classes of society, as well as groups of individuals, may certainly protect their rights, provided this is done by legal means, not violence, and provided that they do no injustice to the inviolable rights of others. All men are brothers. Their differences, therefore, must be settled by friendly agreement, with brotherly love for one another. (Papal Encyclical, Ad Petri Cathedram, 29 June 1959).