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# What is the Cogito?
- URL: https://philocrux.com/glossary/cogito-ergo-sum-definition/
- Published: 2026-05-21T16:01:19.000Z
- Updated: 2026-05-21T16:01:19.000Z
- Description: The Cogito, short for the Latin phrase *Cogito, ergo sum* ("I think, therefore I am"), is the foundational philosophical proposition formulated by René Descartes, asserting that the act of thinking proves the existence of the thinker.
- Author: Philosopheasy
- Tags: Glossary

## The Bedrock of Modern Philosophy

The Cogito is perhaps the most famous phrase in the history of Western philosophy. First written in French as *Je pense, donc je suis* in his 1637 work *Discourse on the Method*, Descartes later formulated it in Latin as *Cogito, ergo sum*. The proposition represents the exact moment where Descartes' radical skepticism hits rock bottom and reverses course, establishing the first undeniable truth of his philosophical system.

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## An Intuition, Not a Syllogism

It is important to note that the Cogito is not a formal logical deduction (a syllogism) like "All humans are mortal; I am human; therefore, I am mortal." If it were a syllogism, it would rely on the premise "Whatever thinks, exists," which would itself be subject to Cartesian doubt. Instead, Descartes conceived the Cogito as an immediate, self-evident intuition. The moment you consciously think, doubt, or even wonder if you exist, you directly experience your own existence. The act of thinking and the existence of the thinker are realized simultaneously as a single, indubitable truth.