Apelles, the famous painter, wished to reproduce the foam from a horse's mouth in a painting. He was not able to get it right, and decided to give up. So, he threw the sponge he used to wipe his brushes against the painting. When the sponge hit the painting, it produced nothing other than an imitation of the horse's foam. In the same way, the Skeptics start off like other philosophers, seeking peace of mind in firmness and confidence in their judgements. When they do not achieve it, they suspend their judgement. No sooner than they do this than, by pure chance, peace of mind accompanies the suspension of judgement, like a shadow follows a body.

Sextus Empiricus