Full Idea
The senses are sometimes deceptive, and it is a mark of prudence never to place our complete trust in those who have deceived us even once.
Gist of Idea
It is prudent never to trust your senses if they have deceived you even once
Source
René Descartes (Meditations [1641], §1.18)
Book Reference
Descartes,René: 'Discourse on Method/The Meditations', ed/tr. Sutcliffe,F.E. [Penguin 1968], p.96