Full Idea
The Cyrenaics, placing all experience within themselves, thought such evidence was insufficient warrant for certainty about reality, and withdrew as in a siege from the world, admitting that objects 'appear', but refusing to pronounce the word 'are'.
Gist of Idea
For the Cyrenaics experience was not enough to give certainty about reality
Source
report of Aristippus the younger (fragments/reports [c.335 BCE]) by Plutarch - 74: Reply to Colotes §1120
Book Reference
Plutarch: 'Moralia - vol 14', ed/tr. Einarson,B. /De Lacy P.H. [Harvard Loeb 1967], p.269
A Reaction
This seems to be the most extreme position found in ancient thought. It accompanies their extreme hedonism, based on the reality of experience and lack of interest in anything external. A bit daft, really.