The subdivision of our social world and the spaces we inhabit into public and private spheres is one of the key features of how a society organizes itself. This affects individuals' mental states and experiences, regulates their behaviour, and superimposes a long lasting structure onto human societies. This book sets out to find out how and why social space is subdivided in this way and to explore the nature of each realm as defined by spatial and symbolic boundaries. To understand this dichotomous organization of space and society, the investigation is conducted along three scales: spatial scale (body, home, neighbourhood, city), degrees of exclusivity and openness (from the most private to the most public), and modes of social encounter and association with space (personal, interpersonal, impersonal). We start from the private, interior space of the mind and move outwards to the extensions of the body in space, the personal space. Then we visit the home, the domains of privacy, intimacy and property, followed by interpersonal spaces of sociability among strangers, communal spaces of the neighbourhood, the material and institutional public sphere and the impersonal spaces of the city. As the shape of the city and the characteristics of urban life are influenced by the way public and private distinction is made, the role of urban designers becomes ever more significant. By establishing a flexible and elaborate boundary between the two realms, urbanism can be enriched, where the danger of encroachment by private interests into the public realm and the threat of public intrusion into the private sphere are both minimized and carefully managed.