We can't even be sure that 1+1=2 or that a triangle has three sides are true because some evil demon might be deceiving us to think such things, when it is possible that even propositions that seem obvious to us might themselves be really false. It is possible that all knowledge of external objects, including our body's, could be false as the result of the actions of an evil demon. It is not, however, possible that we could be deceived about our existence as a thinking thing. The fact that I doubt can't be doubted. Therefore thinking in our minds proves that we exist, regardless whether we have bodies. The body and senses are not essential parts of the self because we can doubt its existence but we can't doubt the existence of the mind. So he concludes that he exists because he thinks: "Cogito ergo sum," I think, therefore I exist. "Cogito ergo sum" is the first certainty Descartes knows. He is certain that he is a thinking thing and he clearly and distinctly perceives this fact. He could not be certain unless all clear and distinct perceptions can be certain. Therefore, he concludes whatever he perceives clearly and distinctly must be true. He further illustrates this point with the wax example by comparing our perceptions of a piece of wax at two times: once while the wax is in a solid state and later after the wax has been melted by a fire. Our knowledge of the solid piece and the melted piece of wax are the same can't come through the senses since all of its sensible properties have changed. Descartes concludes that the perception of the wax is realized neither by sight, nor touch, nor imagination (infinite shapes), but by an act of the intellectual mind alone. .
3. What role does God play in Descartes" epistemological theory? .
In order to be certain that we are not being misled when we claim to know something, Descartes must abandon the evil demon argument. This is done by proving that a perfect, all-powerful God would not permit us to be deceived.
