Plagued with doubt and uncertainty in sensory knowledge, Descartes can be struck with the idea that everything he knows is usually false. He considers the possibility that he has been deceived by an ‘bad demon’ and is remaining with nothing to low fat on, until he arrives at the phrase ‘cogito ergo sum’ (‘I believe, consequently I am’). Clinging to the, he proceeds to reconstruct his doubted world and redefine his understanding. Among the most quoted philosophical works ever sold, Meditations on First Philosophy and Discourse on the technique together display the full workings of Descartes’ sceptical technique and the formation of his well-known phrase. Meditations views him apply the technique in a pursuit to discover indisputable knowledge, while Discourse is certainly his exposition of the technique.