I start in the beginning with Descartes' Cognito ergo sum. I think; therefore, I am. This, I think, is indisputable and proves that I exist, but where can I go from here using reason alone? I acquire verifiable knowledge that I previously did not know and had no way of knowing from sources outside myself. This proves to me that at least one other than I exists. I am not alone and have proved it to my satisfaction using reason alone. Example: I have a friend who comes from a town that I have never heard of. He gives me detailed directions how to get there and then to get to his home and its address. I follow his directions carefully and find the town just as he described it and fine his home with the address that he gave me. There I meet his mother and am invited inside. I see a picture of my friend on a table and his mother tells me details about my friend that I didn't know. I go back and see my friend and he verifies all that his mother told me. Thus, I have satisfactorily proved that not only does my friend exist but also does his mother and the world at least as far as that town exists. But wait a minute, Suppose that it is all a dream put in my head by Descartes' evil demon. I haven't proved anything except that I and at least the demon exists. How can I get beyond this point using reason alone? Let's try a thought experiment. Given infinite time and resources, I can, in principle, read an infinite number of books and talk to an infinite number of people other than myself, gaining infinite knowledge of the world and reality from sources other than myself and verify every detail of all of this knowledge. But, this does not prove that this is not a demon induced dream. If the demon/God is omniscient, all knowing, then he/she/it would be able to put this dream of infinite knowledge gained outside of myself into my mind. Given, in principle, infinite knowledge of all of reality and the dream of infinite knowledge of all of reality, there is no way to distinguish between the two. There is no way, by reason alone, that I could determine if it is real or if it is all a dream. If reality and the dream are completely indistinguishable in every aspect and detail then there can be no way to tell them apart. This is the definition of an identity, I.E. the dream is reality; reality is the dream. Now I apply Oakum's Razor. If they, the dream and reality, are indistinguishable in every respect and detail then one of the terms is redundant and superfluous. Whether we do away with the dream or reality makes no difference; but, since the demon and his dream are a figment of my imagination and cannot be verified to have independent existence, I choose, by reason, to do away with the demon and his dream and choose, instead, to believe in reality as verified by experience and observation. I believe that by this reasoning that I have finally been able to go beyond "Cognito ergo sum" and by reason alone prove the existence of others, the world and reality. Any comments? Is my logic and reasoning faulty? If so, where and can you suggest a way to improve it.