From Writer's Almanac:
Descartes had been a sickly child, spent most of his life staying in bed till noon, got a law degree, then settled in the Netherlands, and in his 20 years there, he did most of the writing for which he is famous.
When he was in his 50s, Queen Christina of Sweden — age 23 — invited him to Stockholm to be her tutor. It was a job that required him to rise at 5 a.m. every day. He was sleep-deprived, caught a fever, and eventually came down with pneumonia, which killed him.
"I think therefore I am"
In 1637, René Descartes said his most famous line, "Cogito ergo sum" — "I think therefore I am."
As a philosophical argument, Descartes wrote that he doubted everything, even his own existence. But he came to realize that the one thing he could not doubt was the existence of his own thoughts. If he was doubting, he was thinking; if he was thinking, then he existed. Hence his famous conclusion: "I think, therefore I am."
The new Auntie Anne's pretzels marketing slogan: "I Snack, Therefore I Am." How times have changed. Image source: own work, Chicago O'Hare Airport, 2010.