India, March 2 -- The remarkable thing about a city is that you are almost always in the company of strangers. That is both its promise and its curse. It is the reason why a city feels liberating and also why it is crushingly atomistic. Strangers are a distinctively urban species. In a city, they are our dwelling and companions.

We communicate with them in many ways. In a crowd we may ask someone to move to the side. In a train we may push politely or nastily. On a beach we may request someone to click our photograph. But the most unintended, the most common and the most surprisingly fruitful way in which we communicate with strangers is by eavesdropping.

Eavesdropping makes you the unofficial archivist of the city. We collect things wh...