When does a heap stop being a heap?
A hundred pebbles is a heap. One pebble isn’t. So where does it change?
About 2,400 years ago, a Greek philosopher usually identified as Eubulides of Miletus is said to have posed a puzzle about a heap of sand.
One grain isn’t a heap. Adding one more grain never seems to turn a non-heap into a heap. Keep adding grains, though, and eventually there’s clearly a heap. So where did it happen?
It became known as the sorites paradox, from the Greek word for heap. A little later, the Stoic philosopher Chrysippus suggested simply going quiet when the answers got uncertain, a bit like pressing the button somewhere in the middle.
Philosophers are still arguing about it. Words like tall, old, bald and heap seem to have no sharp edge, so how do we manage to use them so well?