Full Idea
Stoic epistemologists held that to judge correctly, one must be in possession of a proper criterion of truth - a test that provides invincible evidence of the truth of some belief.
Gist of Idea
Stoics said that correct judgement needs an invincible criterion of truth
Source
report of Stoic school (fragments/reports [c.200 BCE]) by Robert Fogelin - Walking the Tightrope of Reason Ch.4
Book Reference
Fogelin,Robert: 'Walking the Tightrope of Reason' [OUP 2004], p.116
A Reaction
It seems that the Stoics were the first to 'set the bar too high', and inevitably drew the sceptical response that there is no such criterion. The polarisation might go further back, to Parmenides' One (known for certain by reason) and Heraclitus's Flux.