To begin with it should be noted Rene Descartes is outstanding French mathematician, philosopher, physicist and physiologist, the founder of modern analytic geometry and algebraic symbols, as well as the method of radical doubt in philosophy. I think that Descartes succeed in his finding of something certain in the third chapter of Meditations, Descartes formulated his version of the ontological argument for the existence of God as well as the evidence of this argument.
It can be said that Descartes tried to prove the existence of God and find out the basic nature of the material world, because the belief in the existence of the corporeal world is based on the data of our sensory perception. However, firstly you need to find a guarantee of relative reliability of sensory perceptions. As such guarantees can be only a perfect being, who created us with our senses. According to Descartes, we are conscious of ourselves imperfect only because of the idea of measuring ourselves with the all-perfect being. Hence, this idea is not our invention, and is not derived from our experience. Consequently, it could be suggested to us, is embedded in us only by the all-perfect being. On the other hand, this idea is so real that we can divide it into following clear logical elements: the complete perfection is conceivable only under the condition of having all the properties in the highest degree, and hence, the complete reality, which infinitely superior to our own reality, as described in Descartes’s Meditations.
Thus, according to Descartes, a clear idea of all-perfect being displays the reality of the existence of God: firstly, as the source of the idea of him – is a psychological proof. Secondly, as an object, whose properties must be part of reality – is the so-called ontological proof, which is passing from the idea of being the assertion of the existence of imaginable substance. Also, with establishing of all-perfect being as the Creator, Descartes recognizes the relative reliability of our perception of the corporeal world, and builds the idea of matter as a substance or essence, as the opposite spirit. Our senses of material things are not always suitable for determining the nature of the substance. In particular, senses of colors, sounds, and so on are subjective and objective attribute of bodily substances is only in their length, which may be single subject of clear and distinct ideas. It can be seen from the following quote: I experienced in myself a certain capacity for judging which I have doubtless received from God, like all the other things that I possess; and as He could not desire to deceive me, it is clear that He has not given me a faculty that will lead me to err if I use it aright, as stated in Descartes’s Meditations on First Philosophy.
All in all, it should be noted that geometric sided of Descartes’ definition of matter itself is striking enough and elucidated by the latest criticism, but we can not deny that Descartes rightly pointed to the most essential and basic feature of the idea of materiality. By explaining the opposite properties of the reality that we can find in self-consciousness of the minds of the thinking subject, Descartes recognizes the thought as the main attribute of spiritual substance. Both of these substances – mind and matter – for Descartes, with his doctrine of the all-perfect being are finite, created substances. In turn, infinite and the same basic is only the substance God.