"The senses deceive from time to time, and it is prudent never to trust wholly those who have deceived us even once"

This quote by Rene Descartes is a suggestion to be careful and not to trust our senses totally. Our senses can trick us from time to time, and it is smart to be aware of this. We ought to not put excessive faith in our senses, as they can lead us astray. Descartes is alerting us to be careful of those who have actually tricked us in the past, as they might do so again. He is suggesting that we ought to not trust them totally, even if they have actually not tricked us in the past. This is a tip to be conscious of our decisions and to be knowledgeable about the potential for deception. We need to be cautious and not take whatever at face value. Descartes is advising us to be alert and to be aware of the potential for deception, even from those we trust.