... firstly wanted to prove the existence of reality. Like Plato, Descartes was 'leading the mind away from the senses' by observing that the senses deceived him from time to time, and it's prudent never to trust wholly those who have deceived us even once'. Descartes introduces his 'dreaming argument': 'there are no certain marks to distinguish being awake from being asleep'. He had ideas that perhaps the sky, the earth, colours, shapes, sounds and all external things are merely 'the delusions of dreams which he has devised to ensure my judgment'. Again like Plato, he attempts to reconstruct a whole system of reliable knowledge. But first he wanted to prove the existence of a perfect God. He saw God as the source of all truth but the idea of him being the source of all truth and perfection must have been placed in his mind by an actually perfect being-God. ...

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