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 existences. 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 a Being of supreme perfection to my mind) as we are not able to create the idea of a perfect Being this idea must have been planted inside us by God, as a designer leaves a trademark. This argument is substantiated by:
In considering this more attentively, it occurs to me in the first place that I should not be astonished if my intelligence is not capable of comprehending why God acts as He does; and that there is thus no reason to doubt of His existence from the fact that I may perhaps find many other things besides this as to which I am able to understand neither for what reason nor how God has produced them.
For, in the first place, knowing that my nature is extremely feeble and limited, and that the nature of God is on the contrary immense, incomprehensible, and infinite, I have no further difficulty in recognising that there is an infinitude of matters in His power, the causes of which transcend my knowledge; and this reason suffices to convince me that the species of cause termed final, finds no useful employment in physical (or natural) things; for it does not appear to me that I can without temerity seek to investigate the (inscrutable) ends of God.
The trademark argument has been subjected to criticism, John Cottinghams criticism was that he does not have the idea of God in his head therefore God does not exist. Descartes could, however, respond that everyone has the idea of God within them including John Cottingham whether they agree with it or not. A further criticism is similar to the substitution criticism of the ontological argument, it is possible to have the idea of a perfect pizza within ones mind and as it is impossible to conceive of perfection within the limits of reason it must have been placed there by the perfect pizza maker.
Descartes could reply that this argument could only work for God as God has every sort of perfection whereas a perfect pizza would not. William of Ockham, who was responsible for Ockhams razor, could have used this argument against the trademark argument. Ockhams razor states that the simplest form of statement is superior to endless hypotheses It is vain to do with more what can be done with fewer the ontological argument would be simpler if Descartes stated that we all have the idea of a God that exists in our head.
Descartes trademark argument does not prove Gods existence to a satisfactory degree; therefore, Descartes revised Anselms medieval ontological argument to attempt to further prove Gods existence. The second argument Descartes presents for the existence of God is the ontological argument where he says it is necessary that I should attribute to Him every sort of perfection, although I do not get so far as to enumerate them all and this necessity suffices to make me conclude (after having recognised that existence is a perfection) that this first and sovereign being really exists.
This argument put simply means that God is perfect and as it is more perfect to exist than not exist God exists. There are many criticisms of the above argument for the existence of God these include criticisms put forward by Immanuel Kant and the Fideists. Kants criticism was to say, for example Pizzas exist adds nothing to the concept of a Pizza otherwise, it would not be exactly the same thing that exists but something more than we had thought of in the concept; and we could not therefore say that the exact object of my concept exists.
Therefore the concept of a pizza could never be the same as a pizza that exists. If Kants objection is correct the ontological argument fails to prove anything because it is based on the idea that existence is one of Gods attributes and according to Kant existence cannot be one of Gods attributes as it is not a real attribute; existence is not at predicate. Therefore existence does not make God any more perfect.
The criticism offered by Kant warrants the dismissal of the ontological argument as it sets out that existence not being a property does not increase the greatness of God as greatness is measured by somethings attributes. There is however a counter-criticism that, it may be the case that necessary existence is a real attribute and since it is part of Anselms argument that Gods existence is necessary the ontological argument may withstand the criticism.
The ontological argument attempts to prove the existence of God by a priori reasoning this has been criticised by a group of philosophers called the Fideists. The Fideists argue that it is arrogant to assume that something as limited as the human mind is capable of understanding the existence of a being as perfect and infinite as God using reason alone. The Fideists might agree that we can prove by purely logical reasoning that certain things do not exist, it can be proven that square circles and largest primes do not exist.
If it is possible to prove by purely logical means that certain things do not exist it should follow that we can prove by the use of such pure reason that certain things do exist such as an ontological proof for the existence of God. The counter-criticism above makes an analogy between square circles and God which are quite different, the argument of the Fideists is that the idea of God is such that the human mind could not conceive whereas the idea of a square circle is the logical amalgamation of a square and a circle.
The human mind is not capable of conceiving complex theories as infinity, if Thomas Aquinas was correct when he said God is infinite we are incapable of understanding God and therefore unable to prove Gods existence by employing the use of reason. The ontological argument again fails to prove Gods existence to a satisfactory degree, however, Descartes continues to use these proofs of Gods existence to then move on to try to prove the existence of material things, God possesses the power to produce everything that I am capable of perceiving with distinctness, and I have never deemed that anything was impossible for Him.
Descartes proof of the existence of the external world is based solely on Gods existence as he uses God to substantiate his clear and distinct ideas, he says that he can see things in his minds eye, in other words he can conceive of them so maybe the external world really exists. This argument is unconvincing as it is possible to conceive of almost anything in your minds eye such as a Pegasus (a horse with wings) as it is an amalgamation of two clear and distinct ideas, that of a horse and of wings.
This, however, does not mean that it exists as if God has allowed this idea in the mind he must not be the perfect being that Descartes believes in. Descartes said, I do not see how He could be excused of deception if in truth these ideas came from or were produced by causes other than corporeal things. And accordingly one must confess that corporeal things exist. This means that because he can see the external world in his minds eye what he can see must have a cause so that cause must be the external world.
Descartes needed God to prove the existence of corporeal things because God, being a Being of all perfections would not lie to him about the existence of such things. This conclusion to Descartes meditations would have been an acceptable conclusion if he had succeeded to prove the existence of God to a satisfactory degree, however this was not the case so instead his proof of the existence of corporeal things is clouded by a thin veil of theology.
Descartes attempts to extricate himself from his sceptical doubts of the meditations had a varying degree of success, his doubt of his own existence was well surmounted with the indubitable cogito argument. The second of his doubts, that of the existence of God was not extricated as successfully with the unconvincing trademark argument and the out of date ontological argument. Descartes then went on to tackling his doubt regarding the existence of the external world, which was done well but was based on the shady proofs for the existence of God.
Descartes may not have proven the existence of God or the existence of the external world however he did produce a new style of philosophy in which he attempted to base all of his epistemological knowledge (or beliefs) on a single indubitable premise, this style of philosophy now known as foundationalism has been and is still used by philosophers today at great credit to Descartes, Rene Descartes proved himself within this book to be the father of modern philosophy.