RENE DESCARTES (1596-1650)
'I think therefore I am' - 'cogito ergo sum'
'everything which I clearly and distinctly perceive to belong to that thing really does belong to it, is not this a possible basis for another argument to prove the existence of God?' - Descartes, Fifth Meditation, 1641
'Existence is part of the concept of a perfect being' - Descartes, Fifth Meditation, 1641
'Because I cannot conceive God unless as existing, it follows that existence is inseparable from him, and therefore he really exists' - Descartes, Fifth Meditation, 1641