This book is devoted to a very contemporary problem: the lack of exchanges and social interaction between the various fragments that make up the urban mosaic. Paris today is a city that has to reconcile the local and the global, it is marked by a great diversity of ethnic groups. In the description of nineteenth-century Paris, social differentiation was based on class difference. But Paris, like New York or London today, manages its complexities through a regime of social indifference, a culture of dissociation that excludes those who are different. I thought, for this reason, to give this book the title of Difference and indifference, but I finally preferred The Conscience of the Eye, to emphasize the role played by architecture and urbanism in this gap . In modern cities, most social information comes to us. Our society favors images over words; the eye has become our sociological organ.