René Descartes was the first philosopher to introduce the intellectual system known as "radical doubt." According to Descartes, everything he had learned before could have possibly been tainted by society or the senses, therefore he began " to tear down the edifice of knowledge and rebuild it from the foundations up" (Palmer 157). It was not that everything necessarily had to be false, but physical laws could not offer absolute certainty. Therefore Descartes used reason alone as his tool towards gaining absolute truth; truth being something that one could not possibly doubt. In his conclusion, Descartes found that the only thing that holds absolutely true is his existence. His famous quote, "Cogito ergo sum" can be translated into "I think, therefore I am." By this Descartes implied that when you doubt, someone is doubting, and you cannot doubt that you are. With this revelation, the French philosopher continued to define selfhood as his consciousness. For in Descartes terms, it was plausible to doubt that one has a body, but impossible to doubt the existence of one's mind; therefore " self and mind must be identical" (Palmer 162).
Hume on the other hand, took a different approach to the idea of self. He believed that there in fact was no such thing as selfhood.