When does a heap stop being a heap?

Picture a heap of sand — say, a million grains. Remove one grain. Still a heap, obviously; one grain can't make the difference. Remove another. Still a heap. But keep going, one grain at a time, and you reach a lone grain sitting on the table. At no single step did a heap become a non-heap — yet somehow it did. This is the Sorites paradox (from the Greek sōros, "heap"), first posed by the ancient philosopher Eubulides.

The trouble comes from a word that seems perfectly clear but has fuzzy edges. "Heap," "tall," "bald," and "rich" are vague predicates: there's no exact boundary where they switch off. If you insist there is a precise number — say 10,000 grains is a heap but 9,999 isn't — the cutoff feels absurd and arbitrary. Nobody learned the word "heap" that way, and no measurement could reveal such a line.

Philosophers have proposed escapes. Epistemicists say a sharp boundary really exists — we just can't ever know where it is. Advocates of fuzzy logic allow statements to be partly true, so "this is a heap" can shift gradually from 1 toward 0 rather than flipping. Others bite the bullet and deny heaps exist at all. No solution is universally accepted, which is exactly why a pile of sand still troubles logicians.