Adlai Stevenson
Stevenson was a two-time Democratic nominee for President who lost both elections in landslides to Eisenhower. A third bid was thwarted at the primary level by John Kennedy in the 1960 election. Stevenson is perhaps the definitive national example of the pejorative term “egghead” used to describe people who apparently somehow have too much education. He is a vital character in the book due to a 1954 speech containing the line "we are not in danger of becoming slaves any more, but of becoming robots.” That conceptualization of robotic humanity is central to the book’s overall theme.
Emile Durkheim
Durkheim was a social critic and one of the towering figures in the history of sociology. His most essential contribution to the narrative is theory of “anomie” which can usefully be described as the condition of alienation from society which is manifested in the robotic attitudes outlined in Stevenson’s speech which, as stated, forms a foundational element to Fromm’s entire argument.
Karl Marx
Marx is situated as a major character relative to his influence on Fromm’s theoretical condition of the state of sanity of modern Western man. Central to this influence is the Marxian appropriate of “alienation” to which Marx applies as a distance between capitalist workers and the product they make. Fromm expands upon this interpretation to build a much broader basis of 20th century alienation from not just the things a person makes as a worker, but buys as a consumer.
Sigmund Freud
Any discussion of the nation of sanity as a social expression of a group of people as vast and differentiated as “Western culture” written in the first half of the 20th century had better make frequent and serious reference to Sigmund Freud. To do otherwise would practically have guaranteed that it would all but ignored. As a result, Freud and his now-much-more-controversial theories of psychoanalysis is one of the few characters who shows up almost as much as Marx.