The sorites paradox is a paradox that results from vague predicates. A typical formulation involves a heap of sand, from which grains are removed individually. With the assumption that removing a single grain does not cause a heap to become a non-heap, the paradox is to consider what happens when the process is repeated enough times that only one grain remains: is it still a heap? If not, when did it change from a heap to a non-heap?
The sorites paradox: If a heap is reduced by a single grain at a time, the question is: at what exact point does it cease to be considered a heap?
Eubulides of Miletus was a philosopher of the Megarian school who is famous for his paradoxes.
Eubulides