"If you wanted to encounter a set of ideas that were radically different than your own – say those of a confrontational homeless guy who sleeps in a tub – your best bet in an era before telecommunications was to move to a city. Cities are technologies for trade, for learning, for worship, but they’re also a powerful communication technologies. Cities enables realtime communication between different individuals and groups and the rapid diffusion of new ideas and practices to multiple communities. Even in an age of instantaneous digital communications, cities retain their function as a communications technology that enables constant contact with the unfamiliar, strange and different."