Full Idea
Everything that exists consists in being perceived.
Gist of Idea
Everything that exists consists in being perceived
Source
Protagoras (fragments/reports [c.441 BCE]), quoted by Didymus the Blind - Commentary on the Psalms (frags)
Book Reference
'The First Philosophers', ed/tr. Waterfield,Robin [OUP 2000], p.214
A Reaction
A striking anticipation of Berkeley's "esse est percipi" (to be is to be perceived).