In the late nineteenth and early twentieth centuries, prominent social thinkers in France, Germany, and the United States sought to understand the modern world taking shape around them. Although they worked in different national traditions, emphasized different features of modern society, and disagreed about whether Jews were synonymous with or antithetical to those features, they repeatedly invoked the Jews as a touchstone for defining modernity and national identity. In France, Émile Durkheim challenged antisemitic depictions of Jews as agents of revolutionary subversion or counterrevolutionary reaction. In Germany, Karl Marx, Georg Simmel, Werner Sombart, and Max Weber debated the relationship of the Jews to modern industrial capitalism, reproducing in secularized form cultural assumptions derived from Christian theology. In the United States, William Thomas, Robert Park, and their students conceived the modern city in part by reference to the Jewish immigrants concentrating there. In all three countries, real or purported differences between Jews and gentiles were invoked to elucidate key dualisms of modern social thought. The Jews thus became an intermediary through which social thinkers discerned in a roundabout fashion the nature, problems, and trajectory of the wider society. The book proposes a novel explanation for why Jews became a pivotal cultural reference point yet signified such varied and inconsistent meanings; it rethinks previous scholarship on Orientalism, Occidentalism, and European perceptions of America; and it shows that history extends into the present with the Jews—and now the Jewish state—continuing to serve as an intermediary for self-reflection in the twenty-first century.