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哲學功課﹕Proofing the Existence of External World


In this essay, I am going to evaluate Moore’s and Russell’s proof of the existence of external world. I will first outline Moore’s argument and Russell’s argument respectively. Then I will point out the difference in the scope of claim in the two arguments. Moore’s argument asserts a smaller scope of claim than Russell’s, thus it is more defendable. Furthermore, I will propose counter examples to nullify Russell’s argument. At last, I am going to propose my proof to the existence of external world to address the shortcomings in both Russell and Moore’s argument.

On the surface, Moore’s argument is surprise simple. It is so simple that it does not seem to be very convincing. His argument can be illustrated as the following. By holding out two hands, here is one hand and here is another hand. There are two hands exists in front of you. If those hands exist, which is something you cannot deny, there must be external world. [1-p451]

Let’s us understand Moore’s claim a little bit more. Moore’s claim is actually an argument to convince a skeptic who does not believes there is an external world but maintain the belief that there is still an external mind outside of his own mind. In another word, to begin with he has to at least believe that there is other mind, who is trying to convince him that there is an external world, already exists outside of him. Moore’s claim will not work on soloist who does not even believe there is anything outside of his own mind. Moreover, Moore’s claim is based on Kant’s early doubt that “the existence of things outside of us … must be accepted merely on faith, and that if anyone thinks good to doubt their (here, their refer to the external world, not those people) existence, we are unable to counter his doubts by any satisfactory proof.” [1- p439]. Most important of all, Moore’s claim does not survive Descartes style of self-meditation scrutiny. Moore believe there exists an external world and convince the other minds he experience in his external world to believe there really is an external world, but he can never proof to himself that he is not a sole existence that all the external world he experience are merely a product of his own mind.

Moore’s argument is pretty straight forward. He is playing word games on Kant’s argument by separating the definition of the terms use by Kant. He redefines “things outside of us”, “external things” and “things external to our mind” as three separate terms. (Notice that that he uses the term “things outside of US” instead of “things outside of ME”.) He excluded transcendent things from his argument, since that belongs to the department of metaphysics. Then he flipped the argument to equate “external things” to “things not internal to our mind”. Notice this slight change of term is the slate of hand he played to separate “things that can meet in space” from “physical objects” and here is he introduced the term “present in space” which supposed to have a lesser definition than “things that can meet in space”. He used a few examples like shadows, after image to illustrate his points, but I am not going to repeat the arguments here due to the limitation of space. Now, here he plays the finally trick, he used the “two hands” as a common experience shared between two different minds, which the skeptic cannot deny. Since there is a gap between the two minds and now there is a common experience come form that gap, there must be something existence between the two minds originate that experience, so the external world must exist.

Let’s move on to Russell’s argument, if that is qualified an argument. First of all, Russell’s claim is more ambitious than Moorse’s. Russell actually goes one step more to define the nature of external world, which is the existence of matter. Moorse is smart to leave the external world remains undefined which gives him more room to play with his definition tricks. Instead of arguing for the existence of matter, Russell simply makes the instinctive belief assertions without even bother to argue for it. To begin with, one cannot doubt his own existence and the existence of the sense data he experienced. Russell is quite frank to admit that “we can never prove the existence of things other than ourselves and our experience” [2-p.14], then he immediate follow by asserting that “although this is no logically impossible, there is no reason whatever to suppose that it is true.” and appeal to the common sense hypothesis to assert there are external objects that cause our sensations. Here he had commit the two fallacies. First, the appeal to common sense is begging of question. Second, even given that we can indeed somehow rule out the soloist possibility, his so-call argument still suffered from the false dilemma fallacy. He assumes that if we can rule out the soloist hypothesis, our sense data must come from physical objects, but he forgot the origin of experience can skipped the existence layer and come from the transcendent layer directly. For practical reason, we may operate on the “external object exists” instinctive belief proposed by Russell, but he should at least compare and evaluate all alternatives instincts before concluding his particular version of instinct is most simple thus should be the most possible solution.

In [2-p15] and chapter 3, Russell uses more examples to illustrate his instinctive belief of the existence of external object. In [2-p15], he uses the existence of a cat that is independent of his perception as an example. He thinks it is quite natural to think that a cat will continue to exists and feel hungry regardless of his sense-data. There is a famous counter example which is also a cat, Schrodinger’s cat. According to Quantum theory, the wave equation is only collapse at the moment of observation. Strictly speaking, Schrodinger’s cat are free to seize its existence when there is no observer, except that once when it is being observed, its state variable collapse to a known state and catch up with what supposed to happen during the unobservable moments. The Schrodinger’s cat does not sound nature to most people, but it conforms to the laws of quantum physics. Therefore whether something sounds nature or not cannot be used to justify the intrinsic belief. In chapter 3, Russell uses the common between public space and private space to argument for his existence of matter. I can nullify his arguments with two terms, “Virtual Reality” and “Augmented Reality”. In virtual reality, there is no public space and each one’s private space is truly private to him. In augment reality, although there still a public space, but the sense data of the public space can be augmented and altered before it arrive at the private space. In addition, Russell argues that a blind man cannot experience light. With the latest technology, the vision chip, a blind can actually experience light more or less like a seeing person although he never experience lights. The vision chips implanted in his retina stimulate the visual nerve to send image to the brain. In theory the whole visual process can stay digital and electrical without anything related to light. Therefore light must be something that can be reduced and transformed into a set of computer equations and can be recreated using digital processors.

Both Moore and Russell did not give a satisfying proof of the existence of external world to a soloist. I am going to propose my solution in the last paragraph in an attempt to bridge the gap left open in Moore and Russell’s argument. My proof that I am not a lone existence in this world is very simple. If I am alone in this world, no one is going to mark my philosophy paper and I will have no reason to write it. The very fact that I am writing this philosophy paper is the proof that I am not alone in this world, which imply there must exists an external world. Now, assume that there is a philosophy professor who is marking this philosophy paper. The very fact that he is marking this paper also is a proof of the existence of an external world; otherwise he has no reason to mark this paper. In fact, if there is no external world, why would anyone bother to read a paper trying to proof the existence of the external world? Therefore the mere existence of this philosophical paper on its own is the proof of the existence of the external world. Q.E.D.

[1] Paul K. Moser and Arnold Vander Nat, Human Knowledge Classical and Contemporary Approaches, 2003, Oxford Press
[2] Bertrand Russell, The Problems of Philosophy, 1912, Feedbacks

5 comments to 哲學功課﹕Proofing the Existence of External World

  • Have you considered the Matrix/Dreaming argument? If you are living in a Matrix then the fact that “You are writing a Philosophy Paper” is false, because you have not written anything at all, so does the ranking of your paper. A common sense approach towards epistemological skepticism is always looking for an easy way out to the hard problem. I think you are very right to point out that, monist will not find these responses convincing.

    • The professor talked about Matrix in class. If we are plugged into Matrix, there is still an external world, it is just different nature of external world, not real physical object but a computer simulation.

      Here is an more interesting point, if I write a philosophy paper in matrix, am I still writing a paper? Actually, I think I am. I am writing a paper if I use pen and paper, I am still writing a paper if I use keyboard to type. In Matrix, I am just use my brain directly write the paper into the memory of the computer. The paper exists in electronic form inside the Matrix computer.

  • Hm, I think the importance of the Matrix argument points out that: your belief is neither reliable nor justified. It is because when you “think” you are writing a philosophy paper, you “have not” written anything, skepticism points out that the certainty of your “grounds” are without grounds. Following the foundationalist approach, there is “nothing” for you to rely on. If you are interested, Putnam has discussed something very interesting on the Brain in Vat argument. For reference: http://plato.stanford.edu/entries/brain-vat/

  • Lester

    Good stuff! Just want to follow the play and put in my criticism on your final proof. Descartes’ self existence proof goes like ‘I think therefore I am’ although he never said so literally. It means the awareness of the thinking process conclude that ‘I’ the subject must exist. However, it’s pretty much it concluding that ‘I am a thinking thing’.

    Following the same argument, your experience of writing an essay is simply your thought without ground proving the existence of the essay itself. Similar to this message, it does not constitute to the existence of ‘me’ writing you this comment. The whole internet idea can simply be a dream just like the way brought up my Ming. After all, ‘You’ is just a thinking thing and you do not know what goes beyond your thought and whether logic deduces the same way in the next second. (consider it my criticism to Descartes’s later parts in the meditations)

    Anyway, nice blog! Keep up the good work!

    • The essence of the proof is that I can’t prove the existence world to any random people, but I can proof it to the one who marks my paper. I am questioning him what’s the meaning of marking an essay if there is no external world.

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