Intragroup and intergroup differentiation are two basic types of social differentiation. Intragroup differentiation represents a division of the group into subgroups that perform different functions in the group without being superior or inferior to each other. Division of a government into legislative, executive, and judicial branches, or of a university into various departments, exemplifies intragroup differentiation. Another example is the division of labor in a family between husband and wife. When such subgroups become ranked, factually or formally, as “superior” and “inferior,” then intragroup differentiation becomes intragroup stratification.
Intergroup differentiation, on the other hand, is represented by the millions of various organized, semiorganized, and “as if organized” groups, or social systems, into which the total human population is divided and structured (Sorokin  1962, chapters 4, 8, 9). In size and character these groups range all the way from small, local groups such as high school alumni associations up to empires and world religious organizations. Study of all these groups, one by one, would require many generations and would, at best, yield only a catalogue that would obscure the basic group structures and the main lines of mankind’s intergroup differentiation.
Instead of following this fruitless procedure, we must, as is usual in science, employ reduction. This immense variety and number of groups must be scaled down to a limited number, that is, to groups that: (a) are repeated in time and space; (b) are powerful and quite tangibly affect the vitality, mentality, and behavior of large portions of the human population; (c) through their power shape sociocultural life and the historical course of mankind. Study of these important groups provides insight into the elements of intergroup social differentiation and into some of the dynamic forces of social life and human history.
The social systems constituted by these groups have been classified in several different ways (for which see Sorokin  1962, pp. 11Off. and 159 ff. ). Here I will neither review nor criticize these classifications but will merely enumerate, without presenting the reasons for my own classification, the groups that appear to me to be the most “important,” in the above sense of the term.
I Unibonded groups— that is, groups whose members are bound into a solidary system by one main value or interest:
(a) Groups organized, semiorganized, or as if organized around biosocial values, namely (1) race; (2) sex; (3) age. (b) Groups organized, semiorganized, and as if organized around specified sociocultural values, namely (4) kinship groups; (5) groups, such as neighborhoods, based on territorial propinquity; (6) national and ethnic groups, based on community of language, culture, and history; (7) state (that is, governmental) groups; (8) occupational groups; (9) economic groups; (10) religious groups; (11) political parties; (12) ideological and cultural groups (science, philosophy, the fine arts, ethics, education, sport, and so on); (13) a nominal group consisting of the elite (individual men and women of genius, eminent leaders, and historical personages).
II Multibonded groups— that is, groups formed by the coalescence of two or more unibonded values:(a) The main types of family formations (embracing all families of the same type); (b) clans and tribes; (c) nations; (d) castes; (e) social orders ( “estates” ) (f) social classes.
Speaking analogically, we can say that these groups, or social systems, are the main “organs” into which the “body” of the total human population has been differentiated. Each of these groups, in its organized, semiorganized, and as if organized forms, has materially conditioned the vital mental and behavioral characteristics of vast multitudes of human beings and thus has shaped the main forms of social antagonisms and solidarities and the course of human history itself.
Zoological, or racial, constitution, together with sex and age, conditions body, mind, and behavior from within in many ways. The race-age-sex groups, built by sociocultural forces on such bio logical bases, reinforce enormously the influence of these bases and continuously affect personality and life from the cradle to the grave. The antagonisms and solidarities of these groups go on continually, now and then becoming “front-page events” in the annals of history.
Occupational work takes many hours of most adult males’ time and an enormous part of their energy. Daily performance of this work for months, years, and decades quite tangibly shapes in its own image bodily traits and physiological processes; mental, moral, and social characteristics; and overt behavior. This influence is again greatly reinforced by the organized, semiorganized, and as if organized occupational groups (guilds, labor unions, occupational associations and organizations) built for protection and promotion of the occupational interests or values of their members. The antagonisms and solidarities of different occupational groups continually occupy an important place among social antagonisms and alliances; once in a while they flare up into momentous events in the social life of vast populations.
A native language, together with all the mores, folkways, and cultural values imbibed with it from the ethnic group in which its users were born and reared and whose historical and social life they have shared, quite tangibly molds sociocultural personality and conduct. The ethnic and nationality groups, organized for protecting and promoting the social, economic, political, and cultural interests, or values, of their members, notably increase the influence of these ethnic factors. When the membership of an ethnic or nationality group becomes very large and well-organized, the influence of such a group upon the social life of its members as well as on that of outsiders becomes quite considerable and sometimes even momentous in the life history of a large part of the human race.
By its obligatory laws, enforced by a multitude of agents and a coercive power mechanism, the state prescribes and controls almost all the important lines of behavior and interpersonal relationships. The totalitarian states regiment in detail the life of their citizens; the liberal or democratic states do this in a more limited form; but both types of state effectively shape personality and control behavior. Since reaching their full development, states—their policies, alliances, and warshave been for centuries the most salient events of human history. Their influence has grown to such an extent that many historians have reduced the whole mental, moral, cultural, and social history of mankind to a mere political history. Such reduction is entirely unwarranted; nevertheless, it is an eloquent demonstration of the powerful influence of state groups upon the human population and its life history.
A single family is not typically an influential kind of group, but large formations consisting of many families of the same type have certainly been most powerful in forming the personalities and determining the conduct of their millions of members. With proper modification the same can be said of the castes, religious groups, social classes, and other groups enumerated above. Each of them in its own way has been, during long periods, an effective factor in molding the personality, conduct, and historical destiny of large portions of the human population.
Human beings, practically without exception, have always been members, whether voluntary or involuntary, of several of these basic groups. By their combined influence such groups have shaped and are shaping the total personality of every individual—his biological, mental, moral, and social characteristics. No less decisively, these groups determine the individual’s total behavior, since this consists largely in performance of the activities, or “roles,” demanded from him by his membership in these social systems [seeRole, article onSociological Aspects]. Thus, these basic groups that mold all human beings decisively channel the course of the fundamental social processes and the historical destiny of Homo sapiens.
In rudimentary or developed form, one variety or another of social differentiation into these groups has repeatedly occurred in many vast populations and societies. For this reason these lines of differentiation can be regarded as more or less general. This generality does not mean, however, that the influence of each of these groups upon the body, mind, and behavior of multitudes of human beings and upon the course of human history is constant. On the contrary, it fluctuates in time and space, in the sense that each of these groups, or systems, has a different kind and amount of influence in different populations and at different periods in the life history of the same population. In India, for instance, the differentiation of the population into caste groups has been for about two thousand years a most important form of intergroup differentiation and stratification. During this period the caste system has conditioned the personal, social, and cultural life of millions of Indians possibly more powerfully than any other system has conditioned them. In contrast to this, at the earliest period of Indian history caste existed only in rudimentary form as small groups devoid of real power and importance. The Indian caste system has also been losing its influence in recent times, while in many other populations it has not developed as a powerful group at all.
With proper modification the same can be said about the other group—sboth unibonded and multi-bond—edenumerated above. The state and the differentiation of human populations into state groups did not play an important role during the early periods of human history. But ever since its emergence and growth, the state has been one of the most powerful social groups. At the present time, however, its importance is declining, and it is increasingly being replaced by other powerful groups. If and when the existing states are superseded by one “world government,” such a replacement will mean the end of differentiating the human population into different sovereign states, and the state, with all its patriotic values, will decline to the position of an unimportant group stripped of most of its power and glory.
In the medieval period, Christian religious organizations conditioned the mentality, behavior, and sociocultural life of the Western populations much more effectively than they do at the present time. In contrast, scientific groups now play a much more important role than they did in the Middle Ages. Similar fluctuations in influence and importance have happened to groups based on kinship, ethnicity, territorial proximity, occupation, sex, race, and age. Some of these groups, like the caste, the clan, the tribe, and the medieval “estate,” have already passed the zenith of their power, development, and historical role and exist at the present only as largely obsolescent remnants of previously powerful groups.
Of other groups the opposite is true. “Social class,” for instance, is a multibonded type of group whose members are bound together into a solidary unity by similarity of occupational, economic, and sociopolitical interests and activities. Moreover, social class is legally open but actually semiclosed, partly organized but mainly semiorganized, partly aware of its own unity and partly not. Now social class in this sense existed before the eighteenth century only in rudimentary form, and only since then has it grown into one of the most powerful social groups in the Western world. With its growth it has established social class differentiation as one of the deepest lines of intergroup differentiation and the class struggle as one of the most acute forms of intergroup conflict. At the present time, this multibonded group continues to be one of the most important group factors in human history and social life.
These examples show how the influence of each of the basic social groups is liable to fluctuate and how the basic group structures and main lines of intergroup differentiation are continuously changing, whether rapidly or slowly. As the same bits of glass in a kaleidoscope present different patterns when they are rotated, so the same groups present different basic structural configurations and reflect different maps of the main lines of social differentiation at different periods of human history and in divers parts of the human universe.
Despite this variability, the basic group structures and lines of social differentiation at any period of human history have been made up out of different combinations of the unibonded and multibonded groups mentioned above. Thus, at one time in a large part of the human population, a combination of groups based on caste, religion, occupation, language, race, old age, and being of male sex may be the most powerful group structure, dominating the life of this population, its antagonisms, and its solidarities. At another period in the same or a different population, the most powerful group structure may be a combination of groups based on the state, economic factors, occupation, social class, comparatively young age, and being a scientist. At other periods and in other populations, still different combinations of the groups I have mentioned may dominate the historical scene and determine the course of human history in that part of the human universe. It is to be regretted that comparative sociology and history have not as yet prepared a systematic theory of the main types of group structures and lines of differentiation dominant at various periods of human history and in divers parts of the human population. Such a theory would greatly increase our knowledge of the statics and dynamics of human group structures, and of intergroup social differentiation and stratification.
Pitirim A. Sorokin
[Directly related are the entriesConflict, article onSocial aspects; Culture; Reference groups; Social institutions; Social structure; Status, social; Stratification, Social. Other relevant material may be found inCaste; Community-society continua; Democracy; Ethnic groups; Family; Integration, article on social integration; kinship; Occupations and careers; Parties, political; Religious organization; State; Totalitarianism; and in the biographies ofDurkheim; Lenin; Lowie; malinowski; Ross; Simmel; Sorokin; Spencer; Thomas; Thurnwald; Tonnies; Znaniecki. ]
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"Social Differentiation." International Encyclopedia of the Social Sciences. . Encyclopedia.com. (December 17, 2017). http://www.encyclopedia.com/social-sciences/applied-and-social-sciences-magazines/social-differentiation
"Social Differentiation." International Encyclopedia of the Social Sciences. . Retrieved December 17, 2017 from Encyclopedia.com: http://www.encyclopedia.com/social-sciences/applied-and-social-sciences-magazines/social-differentiation
"social differentiation." A Dictionary of Sociology. . Encyclopedia.com. (December 17, 2017). http://www.encyclopedia.com/social-sciences/dictionaries-thesauruses-pictures-and-press-releases/social-differentiation
"social differentiation." A Dictionary of Sociology. . Retrieved December 17, 2017 from Encyclopedia.com: http://www.encyclopedia.com/social-sciences/dictionaries-thesauruses-pictures-and-press-releases/social-differentiation