RENE DESCARTES’ famous statement, cogito ergo sum – I think, therefore I am – was the result of taking his doctrine of universal doubt to extreme levels.
Sitting in his study, Descartes tried to discover what he absolutely, certainly knew to be true, as opposed to what he merely believed to be true. The phrase (which he naturally wrote in French, as Je pense donc je suis) first appeared in his Discourse on Method, published in 1637. Here’s an edited extract from his reasoning:
Seeing that our senses sometimes deceive us, I was willing to suppose that there existed nothing really such as they presented to us… I, convinced that I was as open to error as any other, rejected as false all the reasonings I had hitherto taken for Demonstrations; And finally, when I considered that the very same thoughts (presentations) which we experience when awake may also be experienced when we are asleep… I supposed that all the objects that had ever entered into my mind when awake, had in them no more truth than the illusions of my dreams.
In other words, by the process of systematically doubting everything his senses told him, Descartes arrived at the one truth he could not doubt: that of his own existence. The mere fact that he was thinking these thoughts was proof that he was there to think them.
