‘Cogito Ergo Sum’: The Genesis and Meaning of René Descartes’s Famous Declaration

The influential phrase epitomizes the French philosopher’s search for truth in a world of doubt.
René Descartes contemplates his famous conclusion: Cogito ergo sum.
René Descartes contemplates his famous conclusion: Cogito ergo sum. / Stefano Bianchetti/Corbis via Getty Images (Descartes), fairywong/DigitalVision Vectors/Getty Images (background)

As far as famous philosophical quotes go, René Descartes’s cogito ergo sum—often translated into English as “I think therefore I am”—is up there with Socrates’s “the unexamined life is not worth living” and Friedrich Nietzsche’s “what does not kill me makes me stronger.” But unlike these other quotes, whose meanings are rather obvious, “I think therefore I am” is steeped in Cartesian theory, and its implications are still debated today.

Descartes, born in France in 1596, was raised Roman Catholic. He started his education at the Jesuit College of La Flèche, where he learned Latin and Greek grammar, classical poetry, and ancient history. He read heavily from Cicero, the Roman statesman and orator who defied Julius Caesar in defense of the Republic, and Aristotle, whose logic, ethics, and metaphysics formed the basis for Descartes’s own.  

Religion played a greater role in Descartes’s early years than philosophy. Instead of becoming a lawyer as his family intended, he entered the army and traveled to the Dutch city of Breda to support the Protestant ruler Maurice of Orange in his campaign against Catholic Spain. It was in this climate of unceasing political and religious conflict that Descartes would put I think therefore I am to paper, effectively summarizing his lifelong search for truth and certainty.  

Doubt and Demons: The Origin of Cogito Ergo Sum

Descartes formulated I think therefore I am while working on a 1637 treatise titled “Discourse on the Method of Rightly Conducting One’s Reason and of Seeking Truth in the Sciences.” It was originally published in French, meaning the first iteration of the phrase appeared as puisque je doute, je pense; puisque je pense, j’existe, later shortened to je pense, donc je suis. His choice of language was far from trivial. In an age where scholarship was produced almost exclusively in Latin, Descartes wanted to make his work available to a larger, mostly uneducated audience.

The philosopher wrote “Discourse” out of a growing dissatisfaction with his education and self-education, writing that he found himself “beset by so many doubts and errors that I came to think I had gained nothing from my attempts to become educated but increasing recognition of my ignorance.”

He yearned for a scientific method, which he defined in his 1628 text “From Rules for the Direction of the Mind” as “reliable rules which are easy to apply, and such that if one follows them exactly, one will never take what is false to be true or fruitlessly expend one’s mental efforts, but will gradually and constantly increase one’s knowledge till one arrives at a true understanding of everything within one’s capacity.”

“Discourse” sees Descartes embark on this journey. Supposing himself terrorized by a demon who, unbeknownst to him, causes the world around him to appear differently than it really is, he concludes he cannot in good conscience trust in his own sight, smell, sound, taste, or touch—the foundation of empirical observation and experiments.

René Descartes in Amsterdam
René Descartes in Amsterdam: Thinking, existing. / Culture Club/GettyImages

“Seeing that our senses sometimes deceive us,” he wrote, “I was willing to suppose that there existed nothing really such as they presented to us; and because some men err in reasoning, and fall into paralogisms, even on the simplest matters of geometry, I, convinced that I was as open to error as any other, rejected as false all the reasonings I had hitherto taken for demonstrations.”

Then, in a conclusion leading to his best-known statement:

“Immediately upon this I observed that, whilst I thus wished to think that all was false, it was absolutely necessary that I, who thus thought, should be somewhat; and as I observed that this truth, I think, therefore I am (COGITO ERGO SUM), was so certain and of such evidence that no ground of doubt, however extravagant, could be alleged by the s[k]eptics capable of shaking it, I concluded that I might, without scruple, accept it as the first principle of the philosophy of which I was in search.”

The Meaning of Cogito Ergo Sum

Although Descartes can find reason to doubt his senses, he cannot doubt the act of doubting itself—a claim that is farther reaching than it seems. As Luke Dunne describes in an article for The Collector, the philosopher “doesn’t just think that we are capable of thinking. He also believes that, by virtue of our having the ability to think, we can also justifiably claim to exist.”

As with any accomplished philosopher, Descartes has his share of detractors. Jim Stone, professor emeritus at the University of New Orleans, argues that I think therefore I am is so iconic a phrase that it is not always studied with the scrutiny it deserves. In a 1993 article titled “Cogito Ergo Sum,” he notes Descartes, in treating his maxim as self-evident, never really offers a logical justification for the connection between doubting, thinking, and existence. Why, Stone proposes, is “I think therefore I am” sufficient, but “I suffer therefore I am” is not?

“I believe ‘I am thinking, therefore I am’ does not express an argument,” Stone writes, “but rather a proposition for which Descartes cannot find an appropriate idiom. He resorts to, then abandons, the language of argument and inference as he shifts about trying to express this deeper truth.”

In the grand scheme of things, though, reverence for Descartes far outweighs criticism. Often labeled the first modern philosopher and recognized as a founding father of the Enlightenment, his influence on the development of philosophy might be greater than that of any other thinker, and that is despite—or, on second thought, precisely because—we still don’t have any satisfying answers to the questions he raised.

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