I will be putting up some posts on particular aspects of the Ontological argument that are mentioned in the OCR specification but haven’t turned up in exam questions recently. The first is Descartes’ understanding of existence.
It is necessary to know a little background on Descartes to understand his version of the argument fully. In his book Meditations (1641) he sought to find out what could be known with certainty. To do this he considered all knowledge in a sceptical or doubtful light, doing what is often called now a thought experiment, imagining that he was being deceived by an evil demon. A great condensed version of this is here .
Another excellent resource to understand Descartes is this set of youtube videos . The link opens to the first of five sections. I recommend you start at about 8 minutes into the first one and then watch the whole of part 2 and 3 to really understand how Descartes arrives at the idea of God as a kind of ‘maker’s mark’ in the mind. This was a BBC series called The Great Philosophers presented by Bryan Magee.