Je pense, donc je suis: meaning and origin of Descartes’ quote

Je pense, donc je suis is French for “I think, therefore I am”, the most famous line of René Descartes. It sounds simple, but it hides a whole method for finding what we can be sure of.

Je pense, donc je suis: word for word and in meaning

Word for word, it is “I think, therefore I am”. Je pense means “I think” or “I believe”; donc means “therefore, so”; je suis means “I am”, from the verb être. In Ukrainian the usual translation is «Мислю, отже існую».

The meaning is more precise. Descartes was looking for something he could not doubt. He doubted almost everything: his senses, his books, even whether he was dreaming. But doubting is itself a kind of thinking, and something has to be doing the thinking. So the thinking self must exist.

• Literally: if I think, then I exist.
• More precisely: a thinking thing exists, “I am a thing that thinks” (res cogitans).
• For Descartes this is his first certain principle, the base on which he builds the rest of his philosophy.

• Je pense que tu as raison.“I think you’re right.” After je pense comes que and a clause.
• Je ne pense pas.“I don’t think so.” The negation ne … pas wraps around the verb.
• Tu penses vraiment ça ?“Do you really think so?” French puts a space before the question mark.
• Il est tard, donc on rentre.“It’s late, so we’re going home.” In speech, donc means “so”.
• Je suis fatigué.“I’m tired.” A woman says Je suis fatiguée: the adjective agrees with the speaker’s gender.

Where the quote comes from: Discours de la méthode

The phrase appeared in 1637 in Discours de la méthode (Discourse on the Method). Descartes wrote in French rather than Latin so that educated readers beyond universities could follow him. In Part IV he describes how he reached his first certainty: he rejected everything doubtful and saw that the very act of doubting proves a thinking self.

The Latin form Ego cogito, ergo sum comes from his Principia philosophiae (1644), written in Latin, the language of scholarship at the time. That is why many people know the Latin version, even though Descartes first wrote the idea in French.

The idea is older. Augustine wrote si enim fallor, sum (“if I am mistaken, I exist”) in The City of God. Descartes was not the first, but he made this idea the foundation of his whole system.

How people understand and use it today

Today the line is quoted in philosophy classes, essays on consciousness, photo captions and toasts. In conversation it often sounds playful, especially when someone makes an obvious point sound grand.

A well-known parody is Je consomme, donc je suis, “I consume, therefore I am”, a joke about shopping and consumer culture. In Ukrainian and Russian people make the same joke: «Я купую, отже існую».

Don’t confuse donc (“so, therefore”) with dont (“of which, about which”). They sound almost the same, but le livre dont je parle means “the book I’m talking about”.

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