Short answers, pulled from the story.
Georg Simmel (the 1st of March 1858 - the 26th of September 1918) was a German sociologist, philosopher, and critic regarded as a founding figure of sociology. His neo-Kantian approach helped establish sociological antipositivism, and he pioneered analyses of individuality, social fragmentation, urban life, and social forms. His ideas influenced the Chicago School of sociology and the Frankfurt School's critical theory.
Originally delivered as a lecture at the Dresden cities exhibition in 1903, the essay analyzes how city life transforms the mind of the individual. Simmel argued that the deepest problems of modern life arise from the individual's struggle to maintain independence against the sovereign powers of society. The essay became influential in the 1920s through the Chicago School and gained wider circulation after its English translation appeared in Kurt Wolff's edited collection in the 1950s.
Simmel was denied full academic positions for two main reasons: he was perceived as Jewish during an era of anti-Semitism, and his articles were written for a general audience rather than professional sociologists, which led to dismissive judgements from colleagues. Despite support from Max Weber, Rainer Maria Rilke, Stefan George, and Edmund Husserl, he did not receive an ordinary professorship with a full chair until 1914, at the University of Strassburg.
Simmel defined the stranger as someone who is simultaneously far away and close. The stranger is unknown but near enough to be knowable. Because of this peculiar distance from the group, strangers often perform special tasks others are unwilling to do, such as trade or arbitration, and carry an objectivity that makes them valuable confidants, as people tend to drop their inhibitions around someone they believe is not connected to anyone significant in their social world.
In The Philosophy of Money (1900), Simmel argued that people create value by making objects, separating themselves from those objects, and then trying to overcome that distance. Things too close have no value; things too far away to obtain are also not considered valuable. Scarcity, time, sacrifice, and difficulty all factor into how value is assigned. Simmel also argued that money enables a new form of secrecy through invisible transactions.
Simmel viewed fashion as a social relationship that simultaneously satisfies the desire for conformity and the desire for individuality. He argued that people who try to be unfashionable are practicing an inverse form of imitation: by rejecting the norm, they join a new group that defines itself as different. Genuine individuality therefore keeps eluding those who most deliberately pursue it through dress and style.