"Gregor Fitzi’s book persuasively shows the unity and continuity in Simmel’s thought, whereas often his work has been interpreted as a succession of different phases of development (positivism, neokantianism, philosophy of life) or artificially divided in disciplinary boundaries (sociology, philosophy). The new generation of Simmel scholars is now ready to give up these artificial distinctions which deprives sociological imagination from the stimulus coming from art and metaphysics. A closer scrutiny of Simmel’s sociological theory-building demonstrates that his work takes the form of an ongoing widening of the enquiry into social reality – starting from the analysis of the societal issues in a narrower sense, moving to their socio-cultural implications and premises, and finally turning to the anthropological roots of societal phenomena."Vincenzo Mele, editor of the Simmel Studies"As a motto for a presentation of Simmel’s sociology, I had always imagined the quote: ‘For the social researcher or politician, human is not a problem at all, only humans’. Gregor Fitzi’s book gives a decisive insight into the way Simmel deals with the problem."Otthein Rammstedt, editor of the Collected Works of Georg Simmel "Gregor Fitzi is undoubtedly one of the best connoisseurs of G. Simmel's thought and work. His book, which can rely on the edition of the complete works - to which he contributed - is timely. The presentation of the themes is pedagogical, clear and fluid without abandoning anything of the subtlety of the Simmelian theses; whether they relate to modernity, the philosophy of life, culture or sociology. The Challenge of Modernity will be an invaluable text to the reader interested in the field of sociological theory; whether student, teacher, researcher or public citizen."Patrick Watier, University of Strasbourg