Q0055

René Descartes

A verified English rendering from the curated archive.

English

Once in a lifetime, everything must be doubted.
Thinker René Descartes
School Modern Rationalism
Source Meditations on First Philosophy I
Theme Knowledge
Another quotation More from this thinker

Source context

This English passage is associated with Meditations on First Philosophy I, within the tradition of Modern Rationalism. The wording below is a verified rendering prepared for careful reading rather than a claim of unique translation authority.

A short reading

Read in the register of knowledge, the sentence asks the reader to test an assumption rather than to collect a slogan. In René Descartes's wider work, similar claims are usually offered as prompts for judgment: what would have to be true for the sentence to hold, and what would follow if it did?

How to cite this quotation

APA: René Descartes. (n.d.). Once in a lifetime, everything must be doubted. In Philosophy Blind Box. https://www.philosophydef.com/quotes/q0055

MLA: René Descartes. “Once in a lifetime, everything must be doubted..” Philosophy Blind Box, https://www.philosophydef.com/quotes/q0055.

Chicago: René Descartes. “Once in a lifetime, everything must be doubted..” Philosophy Blind Box. Accessed 2026. https://www.philosophydef.com/quotes/q0055.

Same thinker

More from René Descartes

  1. I think, therefore I am.
  2. The things we conceive very clearly and very distinctly are all true.
  3. Good sense is the best distributed thing in the world.
  4. I am, I exist—whenever it is uttered by me, or conceived in the mind, it is necessarily true.
  5. to change my desires rather than the order of the world

All quotations by René Descartes

Same theme

More on knowledge

  1. What I do not know, I do not claim to know.
  2. No one errs willingly.
  3. What then is time? If no one asks me, I know; if I wish to explain it to one who asks, I do not know.
  4. What do I know?
  5. The world is my representation.

Browse the knowledge theme