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

Rene Descartes draws attention to the fallibility of human perception, suggesting that our senses, sight, hearing, touch, taste, and smell, are not always reliable sources of truth. Throughout our lives, senses occasionally mislead us; distant objects may appear differently, sounds may be distorted, and illusions can trick the eyes. Because these sensory errors occur, Descartes concludes it is wise to maintain a healthy skepticism toward them. Trust naturally dissolves when a source demonstrates unreliability, even sporadically. The same principle he applies to interpersonal relations: if someone deceives us once, we hesitate to trust them unreservedly again. Treating the senses as such an “informant” serves as an initial step in Descartes’s broader philosophical method of doubt.

This skepticism regarding sense perception underpins much of modern philosophy and scientific inquiry. Accepting that appearances can mislead, thinkers are encouraged to seek knowledge that withstands error and uncertainty, knowledge that cannot be shaken by the occasional rebellion of the senses. It urges a move beyond unexamined acceptance of sensory evidence toward critical examination, questioning, and analysis. Descartes’s insight acts as a safety mechanism for the pursuit of truth: if one accepts everything as it seems, errors quickly pile up, hindering understanding.

Additionally, the statement carries ethical undertones, recommending prudence in judgment not only about the world but also about people and experiences that have led us astray. Memory of past deception is intended not to breed cynicism, but caution. Ultimately, this approach to knowledge fosters a humility that acknowledges the limits of our natural faculties while also inspiring the search for foundations of certainty. Through this skepticism, Descartes proposes that knowledge should rest not on fallible senses, but on more stable, rigorous grounds, culminating in his famous “Cogito, ergo sum,” the foundational certainty of thought itself.