Proof that the external world exists?


Solipsism (Photo credit: Nauman Sadiq)

Eric Schwitzgebel is reading Stannis Lem’s novel ‘Solaris’ and discovers in the novel a test of the existence of the external world:

I instructed the satellite to give me the figure of the galactic meridians it was traversing at 22-second intervals while orbiting Solaris, and I specified an answer to five decimal points. Then I sat and waited for the reply. Ten minutes later, it arrived. I tore off the strip of freshly printed paper and hid it in a drawer, taking care not to look at it…. Then I sat down to work out for myself the answer to the question I had posed. For an hour or more, I integrated the equations….

If the figures obtained from the satellite were simply the product of my deranged mind, they could not possibly coincide with [my hand calculations]. My brain might be unhinged, but it could not conceivably complete with the Station’s giant computer and secretly perform calculations requiring several months’ work. Therefore if the figures corresponded, it would follow that the Station’s computer really existed, that I had really used it, and that I was not delirious (1961/1970, p. 50-51).

This is similar to a test Schwitzgebel describes on his blog.

While these tests are interesting, I don’t see how they conclusively prove that solipsism, the belief that we alone exist and all else is an illusion, is false.  It seems like for any test that we could construct, our very evaluation of that test would be based on sensory inputs, which might themselves be an illusion.  But maybe I’m missing something?

Ultimately, I think we all have to take it on faith that the external world exists.  It certainly doesn’t pay to ignore what looks like the external world, since doing so can cause substantial grief and pain.  Maybe that grief and pain is also an illusion, but I find illusory pain just as…painful as the real thing.

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16 Responses to Proof that the external world exists?

  1. agrudzinsky says:

    Solipsism seems impregnable to any tests. For a solipsist, the tests themselves are also a figment of imagination. Descartes’s “I think therefore I am” is also dubious. It could be “I think that I think that I think…” ad infinitum without ever getting to any “therefore”. Not to mention that it’s hard to say what “I” (self) and “am” (being or existence) really mean because “real meaning of reality” seems like a circular concept itself.

    This is why I totally agree with Puglicci that “Last Thursdayism” (a young creationist argument that the world was created “last Thursday” to look like it’s 14bln. years old) is a gem which is impossible to destroy with any scientific tests or data. It’s immune to any amount of reason of any standard, high or low. And, by the way, this is a purely philosophical issue, not a scientific one. Philosophy might save Mr. Harris a lot of efforts trying to refute solipsism experimentally. Hawking also might want to consider digging up philosophy from the grave where he prematurely sent it. It might still be useful to him. Even Carroll who seems to have some regard to philosophy might consider keeping the falsifiability as criterion of science to avoid doing some useless tests or inviting Last Thursdayists into the science club.


    • keithnoback says:

      Yeah, Descartes was a bit confused on the power of reflection. So identity is necessarily comparative and therefore compositional (I am I is a rhetorical tautology). That would seem to preclude real solipsism unless you take that song “We Are the World” literally in which case your solipsism is metaphorical. The most dire conclusion one could reach from that viewpoint is that one’s potential for knowledge is limited somewhat by perspective, and well, duh.;)


  2. Until someone figures out how to get us out of the matrix, it does not matter if it is illusory… death in the illusion is death…


  3. Thanks for confirming my thinking on this.

    agrudzinsky, I like the term “Last Thurdayism”! I’m going to have to remember it next time I get in one of those debates.


  4. SAP, I agree, we can’t craft a completely plausible deductive argument that proves the existence of the external world, but by the same token, neither can we craft a completely plausible deductive argument for solipsism. Given this dilemma the sane thing to do is to take the argument for solipsism as unreasonable — though I’ve had those uncanny moments where solipsism felt like it could be true, but philosophy does not deal in feelings.

    For me, the issue arises due to taking a representationalist stance on mental content — we don’t have epistemic access to the object itself but only to the “idea” of the object in our “mind’s eye” — which opens up the possibility that we can’t be sure the object in itself even exists. I think the correct solution then is to take a Kantian approach and posit that our epistemic concepts are only made possible by our sensory faculties that provide representations, such that epistemic concepts come wrapped up with representations that instantiate them, so it makes no sense to apply our epistemic concepts to the world beyond our sensory experiences of representations. In other words, there is no world to be deduced beyond our sensory experiences, because the rules of logic cannot touch a realm that is not filtered by human consciousness. So the solipsism dilemma isn’t that troubling: either representationalism is false and so solipsism isn’t possible, or representationalism is true and solipsism isn’t very frightening. It might be argued that solipsism is possible with other theories of mental content, but I do think that that our worries about solipsism originate with representationalism suggest that they are co-extensive.

    Thanks for bringing up this topic, SAP. As Agrudzinsky drew attention to, solipsism has interesting questions for epistemology and metaphilosophy.


    • Thanks, and excellent analysis, as always. I think for me, the main issue is that solipsism simply isn’t a productive outlook. Maybe it’s true and everyone but me is an illusion (or to you, everyone but you), but that doesn’t give us any real insight on how to deal with those illusions, if they are in fact illusions. Assuming an outside world just seems simpler.


    • agrudzinsky says:

      …the sane thing to do is to take the argument for solipsism as unreasonable

      “Unreasonable” is a term as ambiguous as “unfalsifiable”. I agree that solipsism is unreasonable, but not because it contradicts any logic. I think, reason and logic do not work to prove anything to a solipsist. It’s worth realizing for people who want to see science swallow everything where reason and evidence are used. Philosophy does not seem to fit this definition well.

      I’m not sure if what we perceive is reality or reality is what we perceive. Quite honestly, I don’t know how to tell the difference. So, division of realism into “direct” and “indirect” does not seem very useful. I love philosophy. It’s amusing that this position of considering these “isms” useless has a name itself — “pragmatism”.

      Quite honestly, I did not know that there is a term “metaphilosophy”. Sure enough,

      Metaphilosophy (sometimes called philosophy of philosophy)…

      — Wikipedia.
      Philosophy of what? What philosophy? 🙂

      I guess, I like philosophy because I often have very weird associations between seemingly unrelated things. For some odd reason, discussions of solipsism reminded me of this imaginary dialogue between Bush and Rice 🙂


  5. George Berkeley discussed this a few hundred years back in his argument for idealism. These anti-solipsism arguments assume mental events cannot be coordinated or obey certain rules. But why assume that? Why assume all mental events are the same as what we call “imagination” ?


  6. To give a totally non-academic answer, I can’t imagine that we’re either rational or irrational enough to imagine the world around us. We’re not rational enough to see all possible logical ends with an accuracy that would enable the world to work (I mean, just look at our attempts to program robots to face real life scenarios), and we’re not irrational enough to handle things that don’t fit patterns – it takes a really talented person or an algorithm to produce something truly random. We’re somewhere in between, and that in betweenness, I think, means we can’t really be the creators of our own perceptions.

    I know that even when I write a story, I’m not really creating something – I’m tapping into strains of things I’ve seen and heard and thought of and reconfiguring it into a new pattern. When I try to be creative, it comes out too formulaic, or too nonsensical to be any good. But when I follow an organic pattern, and let myself be surprised by what comes next, things seem to work out.

    That’s what helps me feel confident in the external world, at least.


    • Excellent insights. When I’ve tried my own hand at fiction, I know the greatest moments are when the story / characters take control and I’m surprised by what’s happening. Like you said, it’s a creation that comes from me, but I can’t contain it. The same is true for computer programs I’ve written. They may have come from me (based on prior inputs I had received at some time in my life), but they take on a life of their own with me only shepherding their development.


  7. nannus says:

    One should indee readd Lem as a philosopher. Solaris, Golem XIV, The Cyberiade, His Master’s Voice (with a similar idea to Solaris) and some others are actualy philosophical books (and very interesting ones).
    The test, of course, is not really valid. In Solaris, the “ocean” creates illusions (or simulations) of people from the past of the people in the station. It can just as well “fake” the numbers on the two sheets of papers the moment they are compared. Reality remains a hypothesis (although, I think, a reasonable one).


    • I think the best sci fi books are often philosophical thought experiments. I’ve never read Lem, having found the old Solaris movie unwatchable, but maybe I’ll rectify that someday.


      • nannus says:

        The film is a different story. Lem himself found it unwatchable. That is Tarkovski. Either you like that kind of non-hollywood film or you don’t.
        I really recommend Lem. His books are different from other SciFi. Some are funny, some are philosophical and some are both. Solaris is a good starting point.


  8. Pingback: Inception (and the experience machine, utilitarianism, and existentialism) | ausomeawestin

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