Proof of the External World

Proof of the External World

To prove the existence of the external world the philosopher G.E. Moore created the proof by the simple example of extending a hand and saying “here is a hand” and then extending another hand and saying “here is another, therefore the external world exists.” By this he sets forth the premises that (1) Here is one hand (2) Here is another hand (3) hands are existing objects (4) therefore the external world exists. The key behind this proof is the fact of saying “here is a hand” and also gesturing with that specific hand. If someone were to say “here is a hand” with the idea of a hand in their mind then this would not prove anything of the external world, but because in Moore’s proof the hand can be thought of in the mind, uttered out loud and specifically pointed to it proves that the external world must exist outside of the mind. Moore says that this is the strongest form of proof of the existence of the external world and challenges anyone to try to think of a better proof, he says in order to be a proof (1) the premises must be different from the conclusion, (2) the premises must be something that is the case, (3) the conclusions must follow that premises given, all of these are satisfied by his proof. He says that this proof can be used to prove the existence of anything in the external world, and also prove of the existence of things in the external world in the past. He does this by saying that he held up two hands not long ago, therefore two hands existed not long ago, therefore at least two external things existed not long ago, therefore the external world exists.

            Many skeptics find problems with Moore’s proof; they say that it has proved nothing. They may give the argument that what if his hands don’t exist, and that he is really just a brain in a vat in some laboratory and the external world of which he perceives as being real is merely an idea in his mind or the computer with which his brain is connected to. That he doesn’t have real hands to raise only the idea and perception of raising his hand which doesn’t exist. They could say that he doesn’t really know that his hand exists, and so his second premise would not be the case and his argument would not be valid.

            An answer to these skeptical arguments in the case of the brain in a vat argument we can target the reliability of perceptions to tell us about the existence of the external world. The skeptics say that perceptions are unreliable and do not give a correct answer to what really exists in the external world. That Moore is really a brain in a vat and his perceptions are wrong about there being two hands in front of him. But these skeptics use these same perceptions of the external world, which are wrong, to say that it doesn’t exist. These skeptics are using, according to them, an unreliable method (perception) of deciding if the external world exists or not.