In Descartes' meditations, Descartes begins what Bernard Williams has called the project of pure enquiry' to discover an indubitable premise or foundation to base his knowledge on, by subjecting everything to a kind of scepticism now known as Cartesian doubt. This is known as foundationalism, where a philosopher basis all epistemological knowledge on an indubitable premise.
Within meditation one Descartes subjects all of his beliefs regarding sensory data and even existence to the strongest and most hyperbolic of doubts. He invokes the notion of the all powerful, malign demon who could be deceiving him regarding sensory experience and even his understanding of the simplest mathematical and logical truths in order to attain an indubitable premise that is epistemologically formidable. In meditation one Descartes has three areas of doubt, doubt of his own existence, doubt of the existence of God, and doubt of the existence of the external world. Descartes' knowledge of these three areas are subjected to three types of scepticism the first where he believes that his senses are being deceived these senses played me false, and it is prudent never to trust entirely those who have once deceived us'. The second of the forms of scepticism revolves around whether Descartes is dreaming or not I see so clearly that there are no conclusive signs by means of which one can distinguish between being awake and being asleep'. The aforementioned malign demon was Descartes third method of doubt as he realised God would not deceive him.
Descartes' search for an underlying foundational premise ends when he realises he exists, at least when he thinks he exists doubtless, then, that I exist and, let him deceive me as he may, he can never bring it about that I am nothing, so long as I shall be conscious that I am something. So that it must, in fine, be maintained, all things being maturely and carefully considered, that this proposition I am, I exist, is necessarily true each time it is expressed by me or conceived in my mind'. This argument I think therefore I am' is Descartes' cogito argument as in Latin it is cogito ergo sum. The cogito argument raises some difficulties, as when thinking results in existence not thinking should therefore result in non-existence leaving the problem of returning to thought from non-existence. Descartes could however reply that the term thought includes the conceiving and perception of all sensory input which is constant, resulting with a human being who thinks non-stop from birth till death removing the problem of dropping out of existence periodically. Human beings are capable of simultaneous thought, this is best illustrated when a person is dreaming as the person will be receiving sensory data from both the external world and from the dream therefore the human is thinking on more than one level at a time which could result in there being two existence's. A further Cartesian response could be that the level of thought or the amount of thought is irrelevant, all that is important is that the thought is being generated by the one individual, therefore it is the one individual that exists. It is seemingly impossible to criticise the cogito argument as every time it is presented to our mind we are forced to assent to it, it may be the case that this argument is infallible or at least indubitable, Descartes therefore has convincingly overcome his doubt of his own existence.
Now that Descartes realised that he was a thinking being he focused his efforts on trying to prove the existence of God for this Descartes has two arguments based on a priori reasoning, the Ontological argument and the Trademark argument.
Descartes first argument for the existence of God is known as the Trademark argument. The argument states that we all have the idea of God in our head ( there is a real and positive idea of God or of...