Erik H. Erikson, the psychoanalyst who profoundly reshaped views of human development, died yesterday at the Rosewood Manor Nursing Home in Harwich, Mass. He was 91. He had a brief illness, said his daughter, Sue Erikson Bloland of Manhattan. A friend and disciple of Sigmund Freud, Mr. Erikson was a thinker whose ideas had effects far beyond psychoanalysis, shaping the emerging fields of child development and life-span studies and reaching into the humanities. He was best known for the theory that each stage of life, from infancy on, is associated with a specific psychological struggle that contributes to a major aspect of personality. That represented a quantum leap in Freudian thought, suggesting that the ego and the sense of identity are shaped over the entire life span and that experiences later in life might help heal the hurts of early childhood. Mr. Erikson's influence, compounded by clinical studies of children, a teaching post at Harvard University, popular lectures and best-selling books on Mohandas K. Gandhi and Martin Luther, pervaded many layers of society, from education to medicine to law to biography to psychiatry to lowbrow culture. His popular recognition reached a peak in the 70's, particularly because of his identification with the development of "identity crisis," a term he coined. But his scholarly contributions have assured him of a place of eminence in many disciplines. The term "psychobiography," which he did not originate, was also associated with his name. His most significant contribution, however, was the concept of a malleable ego in adults, a departure from traditional theories of an ego fixed early in life and persisting to its end. A crucial element in the theory of successive changes in personality, and hence ego modification, was that the dynamics of the society in which a person lived determined to what extent these changes are resolved. By placing the individual in a societal matrix, Mr. Erikson could suggest the degree to which political, economic and social systems, all exterior forces, mold a person's interior emotional life. In that manner he sought a union between psychoanalysis and the social sciences. As a pioneer in the study of the life cycle, Mr. Erikson saw it consisting of these eight crucial stages: In some of his last work, in his 80's, Mr. Erikson worked with his wife, Joan, who lent him an editorial hand throughout his career, to develop a detailed description of just what the lessons of each stage impart to wisdom in old age. They proposed that in the final phase of life, wisdom is achieved to the degree that each earlier phase had positive resolutions. In infancy, for example, the issue is trust versus fearfulness. In old age, that becomes an appreciation of interdependence. The struggle in early childhood between a sense of will and mastery of one's body, on the one hand, and a shame and doubt on the other, becomes in old age, if successfully resolved, an acceptance of the inevitable deterioration of the body. Mr. Erikson theorized that all the crises, including the last, have positive and negative solutions, mediated strongly by milieu and other cultural and societal factors. But whatever the solution, at each stage the crisis has to be resolved if the person is to be unharmed by dread or neurosis. The role of society, and even that of contemporary history, applies directly, at least from adolescence onward. Mr. Erikson's theories were not wholly accepted by Freudians; indeed, the orthodox considered him a heretic. Mr. Erikson himself thought that Freud's daughter, Anna, with whom he had had a special relationship, was unhappy over his departures from the Freudian canon. Other sharpshooters were in the academic community. Many social scientists considered Mr. Erikson ill grounded in their fields. Others doubted his scholarly abilities, partly on the ground that his sole diploma was earned in high school. But Mr. Erikson was serene, believing that his critics did not deal with the substance of his findings and assumptions. He felt compensated, he said, by the attention paid by younger people without credal allegiances. The evolution of his ideas emerged to a definable extent from his life experiences and from a long habit of trusting his artistic eye and his belief in the efficacy of his intuition. Mr. Erikson was born on June 15, 1902, in Frankfurt, Germany, of Danish parents. The common story was that his mother and father had separated before his birth, but the closely guarded fact was that he was his mother's child from an extramarital union. He never saw his birth father or his mother's first husband. When he was 3, his mother was married to his pediatrician, Dr. Theodore Homburger, and throughout his youth he was known as Erik Homburger. He did not learn about his parentage until his teen-age years, "and it was a secret my mother and I shared." To add to the confusion, his adoptive father was Jewish and his mother's heritage was Lutheran. He was reared as a Jew, because his mother and her new husband agreed to treat him as their son. He was also led to think of himself as a German, and his anti-Semitic schoolmates taunted him, while at the synagogue his Jewish friends rejected him because of his Nordic features. As a consequence of compounded identity confusions, he said, he developed "a morbid sensitivity" and often escaped into a fantasy world. After graduating from high school in Karlsruhe, he became an itinerant bohemian, scratching out a living by sketching children. In the process he read eclectically on his own, mostly about art and history. Then, in 1927, he got word from Peter Blos, a classmate and "my oldest friend," who was a child analyst, that there might be a summer job in Vienna as a tutor-companion to the four children of Dorothy Tiffany Burlingham, an American studying with Freud. Mr. Erikson went for the summer and remained to create, with Mr. Blos and Anna Freud, a progressive school in which the students were taught as individuals. Mr. Erikson proved a gifted teacher, with "a knack," as he put it, for empathy with children. Miss Freud, who was pioneering the application of her father's theories to children, singled him out as a potential child analyst and invited him to be her patient. He had, meantime, met Freud at a family party and had gone mushroom hunting with him. Being analyzed by a woman posed problems for Mr. Erikson, but the process, which lasted more than three years, proved beneficial, he said. "Psychoanalysis was not so formal then," he recalled. "I paid Miss Freud $7 a month, and we met almost every day. My analysis, which gave me self-awareness, led me not to fear being myself. We didn't use all those pseudoscientific terms then -- defense mechanism and the like -- so the process of self-awareness, painful at times, emerged in a liberating atmosphere." In 1930 Mr. Erikson married Joan Serson, a dancer and artist, many of whose intellectual interests coincided with his. The marriage helped stabilize Mr. Erikson and turn him further toward child analysis as a career. With his analysis complete by 1933 and his formal training in psychoanalysis also finished, Mr. Erikson left Vienna for the United States. He had a presentiment, he said, of the Nazi terror that was about to descend on Europe, and he was restive about developments in Freudianism, in which Freud's theories were being hardened into beliefs, "and the whole thing was becoming credal." On the boat he learned 800 words of basic English with the aid of George F. Kennan, the diplomat, so that when he arrived in Boston he could make his way around. Child analysis was in its infancy here, so Mr. Erikson had little difficulty in acquiring patients and an appointment at the Harvard Medical School. Mr. Erikson was urged to become more academically acceptable by earning a Ph.D. "I tried for a bit," he recalled, "and then I said the hell with it." He felt that he could learn more from children. "You see a child play," he said, "and it is so close to seeing an artist paint, for in play a child says things without uttering a word. You can see how he solves his problems. You can also see what's wrong. Young children, especially, have enormous creativity, and whatever's in them rises to the surface in free play." Mr. Erikson also worked at the Harvard Psychological Clinic, coming into contact with Margaret Mead, Gregory Bateson and Ruth Benedict, the anthropologists, and Henry Murray and Kurt Lewin, the psychologists. He then went to Yale as a full-time researcher at the Institute of Human Relations and, eventually, as a professor at the medical school. The development of his thought, he said, was from case history to life history to social and cultural factors. In the pursuit of the social and cultural, he left Yale in 1938 to study the early childhood training of the Sioux on a reservation in South Dakota. That was the start of a life concern to demonstrate how the universal events of childhood were affected and molded by society. Later he also studied the Yurok, salmon-fishing Indians in northern California. He found a marked difference between Sioux children, who were reared on tales of game hunting, and the more restrictive childhood of the Yurok, who were prepared for an arduous way of life. In the war years Mr. Erikson studied scores of normal children on the West Coast in an effort to explore psychodynamics through experimental play. Out of that came his initial attempt to relate the Freudian stage theory of infantile sexuality to emergent social capacities and needs in a particular milieu. His proposal that psychoanalysis ought to be a way for understanding "the vicissitudes of normal life" was reinforced in a postwar treatment of emotionally disturbed veterans. Mr. Erikson was impressed by finding that his patients were bewildered and anxious but not mentally ill. They were, he wrote, mostly normal men undergoing the normal crises of readjustment to postwar society. Mr. Erikson elaborated in a paper entitled "Ego Development and Historical Chance," in which he argued that racism and joblessness could affect the mind at the deepest layers of the unconscious and that social and historical factors contributed heavily to an ego's strength or weakness. Mr. Erikson's reputation was limited, however, until the publication in 1950 of "Childhood and Society," which laid out his theories on the stage development of life. The book, which attained a popular audience and established Mr. Erikson as a generative thinker, had profound effects on many educators, psychologists and other specialists who had accepted Freud's views of childhood. The book also helped spur younger analysts to appreciate cultural anthropology and social psychology. Mr. Erikson's concepts, moreover, opened a door to the idea that adults, despite poor childhoods, could compensate for their deprivations. The mold of the first five years of life was not hard and fast. Mr. Erikson's book, which has been a steady seller over the years in many languages, was one anchor of his fame. Two others were "Young Man Luther" (1958) and "Gandhi's Truth" (1969), both psychobiographies in which men of great gifts discover themselves and their roles in relation to their times in adulthood. "Gandhi's Truth" won a Pulitzer Prize and a National Book Award. Before writing those books Mr. Erikson became a cause celebre by leaving the University of California in 1950 rather than sign a loyalty oath. Not a Communist, Mr. Erikson spurned the oath on First Amendment grounds and created a considerable hubbub. He stood fast, and he said later that he felt that his attitude had been among his finest moments. In the McCarthy era Mr. Erikson was a senior staff member at the Austin Riggs Center in Stockbridge, Mass., where he treated severely disturbed young people from well-off families. As a balance, he commuted every other week to Pittsburgh to work with disturbed youngsters from poor families, partly in collaboration with Dr. Benjamin Spock. He also wrote for journals, chiefly about identity, which he defined as a basic confidence in one's inner continuity amid change. A sense of adult identity, he said at one point, "denotes certain comprehensive gains that the individual must have derived from all his pre-adult experiences." The crisis associated with an emergent identity, he suggested, is a normal one and may be accompanied by intense neurotic suffering. In some cases the crisis may be prolonged, especially for creative people. That thinking was applied in Mr. Erikson's study of Luther, in which he focused on Luther's "fit" in a monastery choir as an identity crisis and tried to show how Luther had freed himself from an authoritarian father and the constrictions of Roman Catholicism. Widely praised, the book stirred discussions on the insights of psychobiography as well as its limitations. Critics suggested that for all the light that Mr. Erikson had shed, he had underestimated the cumulative historical forces that produced the Reformation. In the 1960's, Mr. Erikson returned to Harvard as professor of human development. He also conducted behavioral research, lectured at the Massachusetts Institute of Technology and published essays in journals, later put into book form. The books were "Insight and Responsibility" (1964) and "Identity: Youth and Crisis" (1968). His busy life included long sojourns in India, where he became fascinated by the life of Gandhi and wrote, in "Gandhi's Truth," about Gandhi's first use of fasting, in 1918, to win a textile strike. The book tried to show the virtues of nonviolent civil disobedience and centered on Gandhi's middle life, when he became a symbol of the struggle for independence. Mr. Erikson was energized by his study of Gandhi and was led to believe in the possibility of "quite different images of youth and young adulthood" than those prevailing. He was full of hope that "new models of fraternal behavior may come to replace those images of comradeship and courage that have been tied in the past to military service and probably have contributed to a glorification of a kind of warfare doomed to be obsolete in our time." He was optimistic that new models of behavior "would make it possible for adults to contribute true knowledge and genuine experience without assuming an authoritative stance beyond their actual competence and genuine inner authority." He was especially wary of what he saw as a prevailing irrationality among people, young and old, who scorned measured progress as they took direct action to pursue their goals. After his formal retirement in 1970, Mr. Erikson worked on essays, wrote books, lectured and divided his time between California and Cape Cod. In 1987, he and his wife moved from Marin County, Calif., to Cambridge, Mass., because of the founding of the Erik Erikson Center there for scholars and clinicians. The center is affiliated with Cambridge Hospital, part of the Harvard Medical School. His last two books, "The Life Cycle Completed" in 1982 and "Vital Involvement in Old Age," written with his wife and Helen Kivnick in 1986, articulated his ideas on the last stage of life. "A Way of Looking at Things," a collection of his papers edited by Dr. Stephen Schlein, was published in 1987. In addition to his daughter and his wife, of Harwich, surviving are two sons, Kai, of New Haven, and Jon, of Los Osos, Calif.; two sisters, Ruth Hirsch of Manhattan and Ellen Katz of Haifa, Israel, and three grandchildren.