Descartes opens his Principles of Philosophy ↗ (1644) with exactly this thought — Part I, Article 1, in Latin: “Veritatem inquirenti, semel in vita de omnibus, quantum fieri potest, esse dubitandum.” The idea and the sentence are unmistakably his. The familiar “real seeker after truth” English phrasing, however, is a common, unsourced rendering ↗ that matches none of the standard published translations.
“If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things” René Descartes, Principles of Philosophy, Part I, Article 1 (1644). The popular English wording is a common, unattributed translation of the Latin.
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Provenance
The source
Work
Principles of Philosophy (Principia Philosophiae)
Passage
Part I, Article 1
First published
1644, in Latin
Translation
Popular wording is unattributed; Veitch (1850), Haldane & Ross (1934), Miller & Miller (1982) and Cottingham et al. (1985) all differ
If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things.
Descartes’ Latin heading for Part I, Article 1 reads “Veritatem inquirenti, semel in vita de omnibus, quantum fieri potest, esse dubitandum.” John Veitch’s public-domain 1850 translation renders it: “That in order to seek truth, it is necessary once in the course of our life, to doubt, as far as possible, of all things.”
Wikiquote lists the line in its sourced section ↗ under Principles of Philosophy (1644), giving both the Latin and the “real seeker after truth” variant.
WIST’s quotation record ↗ documents the popular wording as a “common, unsourced translation,” distinct from the Veitch, Haldane/Ross, Miller & Miller and Cottingham translations it lists by name.
John Veitch’s public-domain translation, hosted at Project Gutenberg ↗, prints Article 1 as the opening principle of the work.
The underlying work is old and freely reproducible: the 1644 Latin original is long in the public domain, as is John Veitch’s 1850 English translation. But the exact popular wording shown here matches no identifiable published translation, so its own date and copyright status cannot be established — hence “uncertain” for this specific phrasing rather than a public-domain claim.
Fact-check
What gets muddled
This one is genuinely Descartes — the misattribution risk is not who said it but where it comes from and whose English it is.
✕
phrasingThe exact English wording unsourced translation
The flowery “If you would be a real seeker after truth…” version appears endlessly on quote sites but corresponds to no standard scholarly translation. WIST ↗ flags it as a “common, unsourced translation,” separate from Veitch (1850), Haldane/Ross (1934), Miller & Miller (1982) and Cottingham/Stoothoff/Murdoch (1985).
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citationThe source work mis-sourced
It is frequently pinned to the Discourse on Method or the Meditations. It is in fact the very first article of the Principles of Philosophy ↗ (1644), Part I, Article 1.
✓The thought is unmistakably Descartes’ opening principle in the Principles of Philosophy ↗; only the polished English phrasing is of uncertain, unattributed origin.
Context
Why it mattered
This sentence launches Descartes’ program of methodical doubt. Before we can know anything with certainty, he argues, we must once in our lives set aside every belief that could conceivably be false — the senses, received opinion, even mathematics — and see what, if anything, survives.
What survives is the thinker doing the doubting: cogito, ergo sum. The instruction to “doubt all things” is thus not skepticism for its own sake but the first move in rebuilding knowledge on an unshakable foundation.
Doubt everything once, so you can be certain of something after.
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Filed under
More provenance-checked quotes on the same theme, each with its reuse status.
1596–1650 · French philosopher, mathematician, and founder of modern rationalism
René Descartes was a French philosopher, mathematician, and scientist often called the father of modern philosophy. His program of methodical doubt — stripping away every belief that could possibly be false in order to reach an indubitable foundation — leads to his celebrated conclusion, cogito, ergo sum (“I think, therefore I am”). The sentence in question is the very first article of his 1644 Principles of Philosophy, where that doubt-everything method is stated as a principle.
For writers & researchers
Cite this
Primary source — Chicago
René Descartes, Principles of Philosophy, Part I, Article 1 (1644), trans. John Veitch, in Selections from the Principles of Philosophy (Edinburgh, 1850). The popular English wording is an unattributed modern rendering.
MLA (9th ed.)
Descartes, René. Selections from the Principles of Philosophy. Translated by John Veitch, 1850.
APA (7th ed.)
Descartes, R. (1850). Selections from the principles of philosophy (J. Veitch, Trans.). (Original work published 1644)
This verification page
Quotle.info. “Who really said ‘If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things’?” Last verified 10 Jul 2026. https://quotle.info/who-said/if-you-would-be-a-real-seeker-after-truth-it-is-necessary