- Lived:
- 1596–1650 · France, the Dutch Republic, Sweden
- Tradition:
- Early modern rationalism — the "father of modern philosophy," a title this chapter pays out with a full audit
- The Big Idea:
- Doubt everything you possibly can — the world, your body, even mathematics — and you hit one unshakable certainty: the doubting itself. On that bedrock, I think, therefore I am, knowledge can be rebuilt; but the rebuilding splits reality into mind and matter, and philosophy is still trying to glue them back together.
- In their words:
- "Cogito, ergo sum" — "I think, therefore I am."
- If you remember one thing:
- Modern philosophy begins with one man alone in a heated room, tearing down every belief he has to find the one thing that cannot be torn down.