I am," and from this he built a philosophical structure striving for the aforementioned mathematical certainty. However, by the end of the Sixth Medication, Descartes concludes that our knowledge of external objects will always remain imperfect. This does not mean that the Meditations have failed, only that the conclusions to which they have come show the limitations of mathematics in making philosophical judgments and that the Meditations reaffirm the limitations of sensory perception.
Descartes originally asserted that there was only one thing which he could see as certain--his own existence. He later came to see that there were certain innate ideas in the mind, one of which was the idea of God. In his argument in the fifth Meditation, he stated that he could produce in his mind the idea of God just as he could the ideas of shape and number so that he should accord the idea of the existence of God the same certainty he accords mathematics:
. . . whatever proof and argument I use, it must always come back to this, that only the things I conceive clearly and distinctly have the power to convince me completely. And although, among the things I conceive in this way, there are indeed some which are obvious to everyone, while others reveal themselves only to those who consider them more closely and examine them more precisely, nevertheless, after they have once been discovered, the latter are not considered less than the former. . . And, as regards God, if my mind were not already obscured by prejudices, and my thought distracted by the continual presence of the images of sensible objects, there should be nothing that I should know sooner or more easily than him. For is there nothing of itself clearer and more manifest than the existence of a God, that is to say a supreme and perfect being, in the idea of whom along is contained necessary or eternal existence, and who, consequently, exists? (Descartes 146).
In the passag...