The issue at hand: Descartes knows that some things he believes are false. What he doesn’t know is what of his knowledge is false and what of it he can know is true. This is how he begins to question everything he knows and try to peel away the layers of assumptions that he bases his knowledge on.

The method of exploring this issue: The method that Descartes uses in the first meditation is to first try and strip away everything he thinks he knows and try and reach the foundation of all knowledge that he knows to assuredly be true and commence “…anew the work of building form the foundation. “ (Descartes). He goes about stripping away his assumptions by trying to establish whether he can reasonably doubt the truth of each level of knowledge. One he has established that there is good reason to doubt this level of knowledge he moves to the next, until he reaches more and more basic assumptions and types of knowledge. He makes a point of establishing at the beginning of his meditation that “…it will not be necessary for me to show that the whole of these are false…it will be sufficient to justify the rejection of the whole if I shall find in each some ground for doubt.” (Descartes) He asserts this so he will not have to prove each assumption wholly false to suspend belief in it, but merely show that it is doubtful and thus suspend belief in it on the grounds that it is not assuredly true. His method can be summed up as doubt.

The Different Layers of Knowledge: The first layer of knowledge that Descartes tackles is that of sensory information. He recognizes that the senses deceive easily and often and that he cannot place confidence in all that they show him. However he retains at this point that the senses can trick you about things that are “far-removed” from the observer, but that there are other sensory perceptions “presentations of the truth” that are “impossible to doubt” for instance, that he is sitting in a chair by a fire.

He then considers the idea that perhaps these ideas, of being in a chair and by a fire, may not just be a form of insanity. There is in fact, a chance that he is insane, and believes “like those who think they are gourds,” certain facets of reality to be true which are not. He also considers the possibility that is implied by the fact that he has often dreamed (while asleep) that he was in this very chair by this very fire when he was very much not. He concedes that there are now “certain marks by which that state of waking can ever be distinguished from sleep.” This means that the things he now perceives could very well be illusions.

He next moves on to question where such illusions are based. He starts out with the assumption that these illusions must be based on something corporeal. This idea struck me as similar to Plato’s forms. The idea that regardless of the whether the individual object exists; the theoretical idea of it must for an illusion of it, a “painting” as Descartes terms these illusions, must be based on something real.

He then goes on to say that even if you can doubt the fact that these actual objects may not be real, the components of them, more “simple and universal” must be real to have entered our consciousness. For example colors must exist in some form. He also says that the “figure” of corporeal things must exist, such as the number, magnitude, place in time and physical location of things must exist. Here he uses an example of Physics and Medicine versus Arithmetic and Geometry. At this point he has proven Physics and Medicine to be doubtful in nature, but Arithmetic and Geometry still hold true.

He then brings a reason to doubt even these theoretical things by bringing up the idea of an all-powerful God. If there is such a God, how can Descartes be sure that these ideas are not simply wrong perceptions placed in his mind by said God? It is possible that God has placed all he knows in his head and that all of this is merely an illusion orchestrated by God.

However, he finds the idea of a benevolent God to be opposed to such deception. If God is benevolent, why would He deceive all humans to such an extent? He carries this to the logical extension that God, if benevolent, would not allow man to be deceived occasionally. But of course, we are deceived at times. He says that this may mean that there is no “Deity.” But rather than assuming that line of thought he grants that he will assume that there is a Deity and that he is “fabulous” as in incredibly powerful.

Descartes has an intention at this point to assert that the Deity must not be entirely benevolent but rather may very well be a “malignant demon” that is “at once exceedingly potent and deceitful,” and that this Deity only seeks to deceive all of mankind. This is because only this definition of the Deity allows him to truly doubt all that he knows. Thus he reaches the conclusion that he cannot consider any sensory information to be true or any ideas in his head, or any beliefs as there is a reasonable doubt that these were all placed there by the infinitely potent and deceitful evil genius as this “malignant demon” is often termed. This is the foundation he has reached at which none of his original assumptions hold true.