ABSTRACT

Imagine that you woke up one day and found that all the numbers had disappeared from the houses in your town, the cars parked on the streets, and the pages of all the books you own. While social life would not grind to a halt, its gears would turn more slowly. To help someone nd a house, or identify a car, or  ip to a particular page in a book, you would need to give them a description rather than an identier: the red house with the funny-looking roof at the end of the street, the dark green minivan parked on the street that runs by the river, or the page that’s sort of in the middle of the book (a little aer the picture of the aardvark).