See that our senses sometimes deceive us,
I was willing to suppose that nothing existed.
Some men err in reasoning even on the simplest matters of geometry,
although I was convinced that I was as open to error as any other.
All thoughts that had ever entered into my mind when awake,
had in them no more truth than the illusions of my dreams.
As I observed this truth, I think, therefore I am.
I concluded that I might accept it as the first principle
of the philosophy of which I was in search.