He was one of the founders of The William Alanson White Institute of Psychiatry, Psychoanalysis and Psychology in New York City and was associated with the Frankfurt School of critical theory.
Fromm at the time became strongly involved in Zionism, under the influence of the religious Zionist rabbi Nehemia Anton Nobel.
His second important work, Man for Himself: An Inquiry into the Psychology of Ethics, first published in 1947, continued and enriched the ideas of Escape from Freedom.
While working towards his doctorate in sociology at the University of Heidelberg,[11] Fromm studied the Tanya by the founder of Chabad, Rabbi Shneur Zalman of Liadi.
The cornerstone of Fromm's humanistic philosophy is his interpretation of the biblical story of Adam and Eve's exile from the Garden of Eden.
This is why they felt "naked" and "ashamed": they had evolved into human beings, conscious of themselves, their own mortality, and their powerlessness before the forces of nature and society, and no longer united with the universe as they were in their instinctive, pre-human existence as animals.
Drawing from his knowledge of the Torah, Fromm pointed to the story of Jonah, who did not wish to save the residents of Nineveh from the consequences of their sin, as demonstrative of his belief that the qualities of care and responsibility are generally absent from most human relationships.
However, if the economic, social and political conditions... do not offer a basis for the realization of individuality in the sense just mentioned, while at the same time people have lost those ties which gave them security, this lag makes freedom an unbearable burden.
Fromm asserted that these two ways of relating to the world were not instinctive, but an individual's response to the peculiar circumstances of his or her life; he also believed that people are never exclusively one type of orientation.
Fromm writes, "It is the paradox of human existence that man must simultaneously seek for closeness and for independence; for oneness with others and at the same time for the preservation of his uniqueness and particularity.
He identified a discrepancy between early and later Freudian theory: namely that, prior to World War I, Freud had described human drives as a tension between desire and repression, but after the end of the war, began framing human drives as a struggle between biologically universal Life and Death (Eros and Thanatos) instincts.
Fromm's critique of the modern political order and capitalist system led him to seek insights from medieval feudalism.
In Escape from Freedom, he found value in the lack of individual freedom, rigid structure, and obligations required on the members of medieval society: What characterizes medieval in contrast to modern society is its lack of individual freedom…But altogether a person was not free in the modern sense, neither was he alone and isolated.
Building primarily upon the early works of Karl Marx, Fromm sought to re-emphasise the ideal of freedom, missing from most Soviet Marxism and more frequently found in the writings of libertarian socialists and liberal theoreticians.
Fromm's brand of socialism rejected both Western capitalism and Soviet communism, which he saw as dehumanizing, and which resulted in the virtually universal modern phenomenon of alienation.
He became one of the founders of socialist humanism, promoting the early writings of Marx and his humanist messages to the US and Western European public.
In 1965, working to stimulate the Western and Eastern cooperation between Marxist humanists, Fromm published a series of articles entitled Socialist Humanism: An International Symposium.
He joined the Socialist Party of America in the mid-1950s, and did his best to help them provide an alternative viewpoint to McCarthyist trends in some US political thought.
However, as a co-founder of SANE, Fromm's strongest political activism was in the international peace movement, fighting against the nuclear arms race and U.S. involvement in the Vietnam War.
Marcuse also noted that Fromm, as well as his close colleagues Sullivan and Karen Horney, removed Freud's libido theory and other radical concepts, which thus reduced psychoanalysis to a set of idealist ethics, which only embrace the status quo.
[22] Fromm's response, in both The Sane Society[23] and in The Anatomy of Human Destructiveness,[24] argues that Freud indeed deserves substantial credit for recognizing the central importance of the unconscious, but also that he tended to reify his own concepts that depicted the self as the passive outcome of instinct and social control, with minimal volition or variability.
Fromm argues that later scholars such as Marcuse accepted these concepts as dogma, whereas social psychology requires a more dynamic theoretical and empirical approach.