The following is quoted from

Erikson, E.H. (1970). "Identity crisis" in perspective. In E.H. Erikson, Life history and the historical moment. New York: Norton, 1975.

To say then that the identity crisis is psycho and social means that:

1. It is a subjective sense as well as an observable quality of personal sameness and continuity, paired with some belief in the sameness and continuity of some shared world image. As a quality of unself-conscious living, this can be gloriously obvious in a young person who has found himself [sic] as he has found his communality. In him we see emerge a unique unification of what is irreversibly given--that is, body type and temperament, giftedness and vulnerability, infantile models and acquired ideals--with the open choices provided in available roles, occupational possibilities, values offered, mentors met, friendships made, and first sexual encounters.

2. It is a state of being and becoming that can have a highly conscious (and, indeed, self-conscious) quality and yet remain, in its motivational aspects, quite unconscious and beset with the dynamics of conflict. This, in turn, can lead to contradictory mental states, such as a sense of aggravated vulnerability and yet also an expectation of grand individual promise.

3. It is characteristic of a developmental period, before which it cannot come to a head, because the somatic, cognitive, and social preconditions are only then given; and beyond which it must not be unduly delayed, because the next and all future developments depend on it. This stage of life is, of course, adolescence and youth. The advent and solution of the identity crisis thus partially depends on psychobiological factors, which secure the somatic basis for a coherent sense of vital selfhood. On the other hand, psychosocial factors can prolong the crisis (painfully, but not necessarily unduly) where a person's idiosyncratic gifts demand a prolonged search for a corresponding ideological and occupational setting, or where historical change forces a postponement of adult commitment.

4. It is dependent on the past for the resource of strong identifications made in childhood, while it relies on new models encountered in youth, and depends for its conclusion on workable roles offered in young adulthood. In fact, each subsequent stage of adulthood must contribute to its preservation and renewal.

The "socio" part of identity, then, must be accounted for in that communality within which an individual finds himself. No ego is an island to itself. Throughout life the establishment and maintenance of that strength which can reconcile discontinuities and ambiguities depends on the support of parental as well as communal models. For youth depends on the ideological coherence of the world it is meant to take over, and therefore is sensitively aware of whether the system is strong enough in its traditional form to "confirm" and to be confirmed by the identity process, or so rigid or brittle as to suggest renovation, reformation, or revolution. Psychosocial identity, then, also has a psycho-historical side, and suggests the study of how life histories are inextricably interwoven with history. The study of psychosocial identity, therefore, depends on three complementarities--or are they three aspects of one complementarity?--namely, the personal coherence of the individual and role integration in his group; his guiding images and the ideologies of his time; his life history--and the historical moment.

All this sounds probable enough and, especially when shorn of its unconscious dimension, appears to be widely, and sometimes faddishly, acceptable in our day. The unconscious complexities often ignored can be grouped thus:

1. Identity formation normatively has its dark and negative side, which throughout life can remain an unruly part of the total identity. Every person and every group harbors a negative identity as the sum of all those identifications and identity fragments which the individual had to submerge in himself as undesirable or irreconcilable or which his group has taught him to perceive as the mark of fatal "difference" in sex role or race, in class or religion. In the event of aggravated crises, an individual (or, indeed, a group) may despair of the ability to contain these negative elements in a positive identity. A specific rage can be aroused wherever identity development thus loses the promise of an assured wholeness: an as yet uncommitted delinquent, if denied any chance of communal integration, may become a "confirmed" criminal. In periods of collective crisis, such potential rage is shared by many and is easily exploited by psychopathic leaders, who become the models of a sudden surrender to total doctrines and dogmas in which the negative identity appears to be the desirable and the dominant one: thus the Nazis fanatically cultivated what the victorious West as well as the more refined Germans had come to decry as "typically German." The rage aroused by threatened identity loss can explode in the arbitrary violence of mobs, or it can--less consciously--serve the efficient destructiveness of the machinery of oppression and war.

2. In some young people, in some classes, at some periods in history, the personal identity crisis will be noiseless and contained within the rituals of passage marking a second birth; while in other people, classes, and periods, the crisis will be clearly marked off as a critical period intensified by collective strife or epidemic tension. Thus, the nature of the identity conflict often depends on the latent panic or, indeed, the intrinsic promise pervading a historical period. Some periods in history become identity vacua caused by the three basic forms of human apprehension: fears aroused by new facts, such as discoveries and inventions (including weapons), which radically expand and change the whole world image; anxieties aroused by symbolic dangers vaguely perceived as a consequence of the decay of existing ideologies; and, in the wake of disintegrating faith, the dread of an existential abyss devoid of spiritual meaning. But then, again, a historical period may (as, for example, the American Revolution did) present a singular chance for a collective renewal which opens up unlimited identities for those who, by a combination of unruliness, giftedness, and competence, represent a new leadership, a new elite, and new types rising to dominance in a new people.

If there is something to all this, why would insights concerning such universal matters first come from psychoanalysis, a clinical science? The fact is that in all periods of history, mental disturbances of epidemiological significance or special fascination highlight a specific aspect of man's nature in conflict with "the times" and are met with by innovative insights: as happened to hysteria in Freud's early days. In our time, a state of identity confusion, not abnormal in itself, often seems to be accompanied by all the neurotic or near psychotic symptoms to which a young person is prone on the basis of constitution, early fate, and malignant circumstance. In fact, young individuals are subject to a more malignant disturbance than might have manifested itself during other stages of life, precisely because the adolescent process can induce the individual semi-deliberately to give in to some of his most regressed or repressed tendencies in order, as it were, to test rock bottom and to recover some of his as yet undeveloped childhood strengths. This, however, is safe only where a relatively stable society provides collective experiences of a ceremonial character, or where revolutionary leaders (such as Luther) provide new identity guidelines which permit the adolescent individual to take chances with himself. Historical crises, in turn, aggravate personal crises; and, indeed many young people have in the recent past been judged to suffer from a chronic malignant disturbance, where we now know that an aggravated developmental crisis was dominant. This, then, is the clinical anchorage for the conception of an identity crisis. (Erikson, 1970/1975, pp. 18-22)