It’s a sunny spring day in 1909 at the Stadtpark in Vienna. Leon Trotsky, fresh off another jailbreak, kicks a soccer ball toward his kids and waves back at his wife, who’s sprawled beneath a maple tree on a picnic blanket with another couple. Trotsky waltzes over and chats with his friend, one of the most renowned psychoanalysts in all of Vienna. No, not Sigmund Freud — the man with Trotsky would actually be expelled from Freud’s inner circle two years later. But while he’s less remembered today, he remained highly influential on an international scale for decades, his ideas taking center stage during the city’s interwar socialist period known as Red Vienna. This man was Alfred Adler.

Adler’s break with Freud in 1911 was a long time coming. He had joined Freud’s famous Wednesday Psychological Society at its inception in 1902, but over the course of the next decade, the two men’s thought diverged. Adler had entered the group already a socialist, and his political views shaped his psychological thought. Freud, meanwhile, preferred to keep politics out of the clinic. Because of Adler’s early involvement in the group and his widely recognized clinical skill, he felt empowered to challenge Freud. But Freud found the challenge increasingly frustrating, and eventually the group dynamic became untenable.

Adler entered the Viennese stage in 1898, with his first professional publication at the age of twenty-eight. His Health Book for the Tailor Trade aimed “to describe the connection between the economic condition of a trade and its disease, and the dangers for public health of a lowered standard of living.” Adler outlined the diseases common to Viennese tailors, their etiologies, their psychological impacts, and the potential of various reforms to improve workers’ lives. He examined how industrialization had changed the tailor trade and argued in favor of robust government regulation to improve conditions and rights for workers. At the start of his career, Adler was already emphasizing the social aspect of disease and advocating for a more preventative type of medicine, both biologically and socially.