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Who really said it

I think, therefore I am

Written by René Descartes 1596–1650 · French philosopher & mathematician
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Genuinely his. Descartes wrote it in French as “Je pense, donc je suis” in the first paragraph of Part IV of the Discourse on the Method (1637). “I think, therefore I am” is the standard English translation — the form popularised by the Haldane & Ross 1911 edition.

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“I think, therefore I am” René Descartes, Discourse on the Method, Part IV (1637)

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Provenance

The source

Work
Discourse on the Method
Passage
Part IV, opening paragraph
First published
1637 (Leiden), in French
Original
“Je pense, donc je suis”
Translation
“I think, therefore I am” — standard English form (Haldane & Ross, 1911)

…I observed that whilst I thus wished to think all things false, it was absolutely essential that the ‘I’ who thought this should be somewhat; and remarking that this truth, ‘I think, therefore I am,’ was so certain and so assured that all the most extravagant suppositions brought forward by the sceptics were incapable of shaking it, I came to the conclusion that I could receive it without scruple as the first principle of the Philosophy for which I was seeking. Part IV

Part IV of the Discourse, in the Haldane & Ross (1911) translation. The French original reads “…cette vérité, je pense, donc je suis…”

Wikipedia: Cogito, ergo sum — sources and translation history

How we know

  • Wikiquote’s sourced section attributes “I think, therefore I am” / “Je pense, donc je suis” to the Discours de la Méthode (1637).
  • Wikipedia’s “Cogito, ergo sum” confirms the phrase “first appeared (in French) … in the first paragraph of its fourth part,” and that the Latin form came later.
  • The same article notes John Veitch’s 1850 translation rendered it “I think, hence I am,” while the Haldane & Ross 1911 translation established the now-standard “I think, therefore I am.”
Public domain

The French original was first published in 1637 and is long in the public domain. The standard English wording “I think, therefore I am” comes from the Haldane & Ross translation of 1911 — also public domain in the United States (published before 1931).

This reflects the original work, which is public domain. If your exact English wording comes from a specific modern translation, that translation may itself still be under copyright — check the edition you quote.

Fact-check

The common misconception

The attribution to Descartes is correct — but almost everyone misremembers how and where he said it.

Descartes — but in French, not Latin Wrong language

In the 1637 Discourse on the Method he wrote “je pense, donc je suis” in French. The Latin “cogito, ergo sum” appears only later — in the 1644 Latin edition of the Discourse and, as “ego cogito, ergo sum,” in the Principles of Philosophy (1644, Part I, art. 7).

Not in the Meditations Wrong book

His best-known work, the Meditations on First Philosophy (1641), never states the familiar phrase; there the certainty is expressed as “Ego sum, ego existo” — “I am, I exist”.

So: really Descartes, really his idea and his words — but the original is French (“je pense, donc je suis”) in the 1637 Discourse, and the Latin “cogito, ergo sum” came seven years later.

Context

Why it mattered

Descartes was hunting for one belief that could survive total, systematic doubt — a bedrock certain enough to rebuild all knowledge on. Even a deceiving demon, he reasoned, could not trick him into thinking he existed if he did not: the very act of doubting proves a doubter. That single fixed point — “I think, therefore I am” — became the first principle of modern Western philosophy.

The line marks a turning inward: certainty is founded not on the external world or authority but on the thinking self. It is why Descartes is so often called the father of modern philosophy.

The one thing doubt cannot touch is that there is someone doing the doubting.

Explore

Filed under

More provenance-checked quotes on the same theme, each with its reuse status.

Truth Knowledge

Go further

Dig deeper

Trusted places to keep pulling the thread — primary archives, fact-checks, and scholarship. We show how we used each one before you leave.

Wikiquote: René Descartes (sourced)en.wikiquote.org

Sourced entry attributing “Je pense, donc je suis” / “I think, therefore I am” to the Discourse on the Method (1637).
Wikipedia: Cogito, ergo sumen.wikipedia.org

Chronology of the French original, the later Latin forms, and the English translation history (Veitch 1850, Haldane & Ross 1911).
Project Gutenberg: A Discourse on Methodgutenberg.org

Full public-domain text of the Discourse (Veitch translation) containing the Part IV passage.
Britannica: Cogito, ergo sumbritannica.com

Encyclopedia overview of the phrase, its meaning, and its place in Descartes’s method of doubt.
Stanford Encyclopedia: Descartes’ Epistemologyplato.stanford.edu

Scholarly treatment of the cogito and its role in Descartes’s foundational program.
Mental Floss: The genesis of ‘Cogito Ergo Sum’mentalfloss.com

Popular history noting the earliest French wording “puisque je pense, j’existe” shortened to “je pense, donc je suis.”

The true author

About René Descartes

René Descartes

1596–1650 · French philosopher, mathematician & scientist

René Descartes (1596–1650) was a French philosopher, mathematician and scientist often called the father of modern philosophy. In the Discourse on the Method (1637) and Meditations on First Philosophy (1641) he pursued a program of radical doubt, arriving at the thinking self as the one thing that cannot be doubted. He also gave us Cartesian coordinates, linking algebra and geometry.

For writers & researchers

Cite this

Primary source — Chicago

René Descartes, Discourse on the Method, Part IV (Leiden, 1637); “je pense, donc je suis.” English: The Philosophical Works of Descartes, trans. Elizabeth S. Haldane & G. R. T. Ross (Cambridge, 1911).

MLA (9th ed.)

Descartes, René. The Philosophical Works of Descartes. Translated by Elizabeth S. Haldane and G. R. T. Ross, Cambridge, 1911.

APA (7th ed.)

Descartes, R. (1911). The philosophical works of Descartes (E. S. Haldane & G. R. T. Ross, Trans.). Cambridge. (Original work published 1637)

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