Arlene was having trouble with her homework in philosophy class. “We’re studying Descartes,” she said. “He starts out with cogito, ergo sum — I think, therefore I am — and ends up proving the existence of God.”
“Impossible!” I said, without stopping to think that I was doubting the great Descartes. It was a reaction I learnt from my father: Have no respect whatsoever for authority. Instead, look at what he starts with, where he ends up, and ask yourself, “Is it reasonable?”
I said, “How can you deduce one from the other?”
“I don’t know,” she said.
“Well, let’s look it over,” I said. “What’s the argument?” So we look it over, and we see that Descartes’ statement, cogito, ergo sum, is supposed to mean that there is one thing that cannot be doubted — doubt itself. “Why doesn’t he just say it straight?” I complained. “He just means that he has one fact that he knows.”
Then he goes on and says things like, “I can only imagine imperfect thoughts, but imperfect can only be understood as referent to the perfect. Hence the perfect must exist somewhere.” He’s working his way towards God now.
“Not at all!” I say. “In science you can talk about relative degrees of approximation without having a perfect theory.”
“What Do You Care What Other People Think?” by Richard P. Feynman, Bantam Books © 1988