Skepticism is the view that there is no way to prove that objects exist outside of us. Skeptics argue that we cannot distinguish between dreams and reality, and therefore what we consider to be true may very well be a creation of our mind while we are nothing more than a simple piece of matter, like a brain sitting in a vat that is connected to a machine which simulates a perfect representation of the reality in which the “brain” can live.1 In the passage “Proof of an external world” taken from his essay of the same name, GE Moore responds to the skeptic's argument by attempting to demonstrate the existence of external objects. There are four parts to this document. First, I will explain Moore's overall argumentative strategy and how he views his proof as rigorous and legitimate. Next I will present Moore's proof of the existence of an external world. Third, I will discuss the responses that skeptics might have to Moore's argument and how Moore defends his evidence against these responses. Finally, I will give my opinion on how effectively Moore defends his claims against skeptics' responses. Moore argues that there is an external world by providing a simple and believable situation that makes the existence of an external world seem obvious (this will be clarified in the next section). He then demonstrates that it satisfies the three conditions that ensure rigorous and legitimate proof: that the premise and the conclusion are different, that the premise was something he knew to be true, and that the conclusion follows logically from the premise (GSC 359). Moore even states that this type of evidence can answer many different questions involving issues surrounded by doubt. For example, Moore creates a scenario in which… halfway down the paper… we understand that the “father” of modern skepticism, René Descartes, wrote in his First Meditation that “firmly rooted in [his] mind is the belief long-standing that there is an omnipotent God” (GSC 353). existence of external objects by providing a simple example of raising one's hands and demonstrating that it satisfies the three conditions of a rigorous and legitimate proof. He successfully combats potential criticism from skeptics by attributing to his belief the awareness of raising one's hands and saying "Here's mine hand" (the premise of his proof), something that Descartes, whose First Meditation makes the case for modern skepticism, has in the existence of God.