Some concept of class appears to be fundamental to modern sociology whether explicitly or as "group", "caste", etc., but there are two ways in which 'class' can be used and often a certain confusion results. 'Class' can be used to mean either:
The former is class in the objective or mathematical sense; the second might be called class in the subjective or psychological sense. Plainly a class in the mathematical sense need not define one in the psychological sense and there may be no (non-circular) definition of a class in the mathematical sense corresponding to a particular class in the psychological sense.
Needless to say the classes dealt with in sociology are not pure. A class in the objective sense may have a varying degree of subjective class character depending on circumstances. A class in the subjective sense may form which cuts across several obvious class barriers in the objective sense, but may later come to coincide roughly with a class in the objective sense as classes in the mathematical sense may overlap or include others since the division may be purely conventional. (However it is usual at any stage to operate with mutually exclusive and exhaustive classifications in terms of socially relevant characteristics.) Empirically however it is found that certain classes in the first sense are often associated with classes in the second sense. This can sometimes be historically understood from situations in which the two classes were originally identical or where a class in the objective sense suddenly acquired significance from new events or ideas. Four principles of objective division having a high correlation with subjective perception are:
Economic class is fairly basic to sociological investigation and in most societies the economic stratification is fairly obvious. Economic principles of division may be in terms of difference in general economic function or in terms of a catalogue of different occupations; in terms of income level or source; in terms of income origin by economic sector e.g. primary/secondary/tertiary or production/exchange, etc. Most but not all of these correlate in the societies where they are useful with divisions between income groups.
Racial divisions are not as objective as economic ones in that what is felt as a racial division in a society may have doubtful status. All the same in most societies in which there are two or more races stratification develops. This may be horizontal or vertical; e.g. the Jews in America had virtually their own parallel society whereas the Negroes, although internally stratified, are still considered a lower class in all senses. Sometimes without obvious and drastic stratification a particular racial group may monopolise a certain function in society, e.g. chinese merchants in South-East Asia.
Religious divisions in society are felt in almost the same way as racial ones. In extreme cases there is horizontal or vertical segregation as in the case of the Jews or the Moslems and Hindus. Certain organisations in less extremely divided societies may partake of a definite religious colouration - e.g. the DLP and the catholics or the KKK and the southern methodists - and certain religions may be discriminated against - e.g. the business community and catholics. The ideologies or dogmas expounded by religious groups however are a factor absent from purely racial ones.
Political divisions are obvious in international issues where national feeling tends to override other divisions but there are other political divisions which correlate more closely with the above. These are the divisions corresponding to the possession or non-possession of (internal) political power. It is rarely that a purely political stratification will be felt i.e. define a class in the pshychological sense - to the exclusion of other types of division but it can happen that the most important division in a society becomes that between administration (or army) and people in which case the government must almost certainly fall.
Most of the other principles of division correlate with that in terms of political power since, as Marx pointed out, economic power constitutes political power in bourgeois society and political power gives economic advantage in feudal (or managerial) society. In many societies also racial divisions correspond to power divisions - but not necessary to economic ones. The same holds for religious divisions since a religion maybe part of the establishment or politics the secular arm of religion.
For these reasons simple economic divisions are not necessarily the fundamental ones; indeed much of C20th history is understood in terms of racial, religious and political divisions. The separation of India and Pakistan; the Indonesian revolution; the rebellion in Ghana; the negro question in the USA and the problem of the French-Canadians are not connected with class conflict in any obvious way. (Although it may be claimed that an economically motivated imperial world policy created these problems).
The usual problem today is that of a racial or religious group struggling to hold or extend its economic or political power (usually the latter). Countries where the economic issue is paramount are usually feudal or non-capitalist or capital countries with rigid political divisions.
The central issue is that of power i.e. of political class divisions. By the conquest of power economic issues can be resolved by the imposition of a solution from above, e.g. communists try to over-throw capitalist by seizing power through non-constitution means, socialists try to do it by reforms within the system. From political power however new divisions arise - hence a managerial class has been thought to be arising. It almost certainly is the case that a class having power, e.g. a party or an administration, will be economically favoured and may develop or originally have a racial or religious character. In this way racial or religious superiorities may be established or maintained.