Erikson started from Sigmund Freud's theory of the libidinal stages of psychosexual development and widened it from the zones of the body to the social tasks of each period of life. In Childhood and Society he recast the libidinal stages as a scheme of zones and modes. Each bodily zone carries a mode of approach, such as taking in, holding on, letting go or intruding, and each mode becomes a pattern of social behaviour. He read a case history on three interlocking levels, the organism, the ego and society, none of which explains a symptom on its own. Every society, he argued, meets the child's bodily stages with its own methods of child training, suited to its economy and its image of the world. Among the Sioux and the Yurok he showed how the child training of a buffalo-hunting and of a salmon-fishing people fitted their ways of life. The Sioux, cut off from their historical way of life, were left without an identity they could live by (Childhood and Society2).
The chapter "Eight Ages of Man" in the same book set out the life cycle as eight stages, each posing a crisis between two outcomes. They are basic trust versus mistrust, autonomy versus shame and doubt, initiative versus guilt, industry versus inferiority, identity versus role confusion, intimacy versus isolation, generativity versus stagnation, and ego integrity versus despair (Childhood and Society2). The memorial minute notes that the first five stages correspond to Freud's, and that Erikson added the last three, those of young adulthood, adulthood and maturity (Harvard memorial minute1). Under the epigenetic principle that orders the scheme, each stage has its own time of ascendancy but depends on how earlier stages were resolved. Late in life Erikson restated the scheme in The Life Cycle Completed7 (1982). There he gave the basic strength that each stage yields and paid closer attention to old age and to the relation between the generations.
Identity was the centre of the scheme. Erikson first used the term ego identity in "Ego Development and Historical Change" (1946) and treated it most fully in "The Problem of Ego Identity" (1956). Both papers were reprinted in Identity and the Life Cycle8 (1959). In Childhood and Society he defined the task of adolescence as an inner sense of sameness and continuity that matches the sameness and continuity of one's meaning for others. The failure of this task he called role confusion. In the 1956 paper he described it as identity diffusion, and later he preferred the term identity confusion. Society, in his account, grants the young a psychosocial moratorium, a delay of adult commitments in which roles and beliefs can be tried out. Identity: Youth and Crisis5 (1968) was his fullest statement of the theory. It covers identity formation across the life cycle, the adolescent crisis and its pathological forms, and identity in relation to race, gender and the youth movements of the 1960s. In middle adulthood the theme is generativity, the concern with establishing and guiding the next generation.
Erikson also carried the idea of identity from the individual into history. The last part of Childhood and Society reads the polarities of American identity, Hitler's imagery of his own childhood and a Soviet film of Maxim Gorky's youth as expressions of national identities. Young Man Luther9 (1958) reads Luther's crisis in the monastery as a prolonged identity crisis and moratorium, whose resolution became a turning point in religious history. Gandhi's Truth3 (1969) centres on the Ahmedabad textile strike of 1918. It traces how Gandhi's generativity in middle life, and his method of nonviolent resistance, grew out of his personal history and his times. Both books read a leader's personal crises together with the historical crises of the age, and they became the model for psychohistory.