On Philosophy

June 20, 2007

The Unknowablility Of The Non-Physical World

Filed under: Mind — Peter @ 12:00 am

Here I will be arguing that the thesis that there is some non-physical stuff in addition to the physical stuff of the universe that explains the existence and nature of consciousness (and possibly other things as well) doesn’t actually explains what it sets out to explain, and thus is a bad philosophical theory. Well, actually that is a bit of an exaggeration. Really what I am showing is that it can’t explain why we believe (intuitively) that such stuff exists, independently of how well that stuff happens to explain consciousness (and whatever else it is used to explain). Even given that it could still turn out to be such a wonderful explanation of consciousness that we accept it anyways, as the best explanation we have, despite the lack of direct evidence for it. However theories that invoke non-physical stuff to explain consciousness generally do a terrible job at explaining the nature of consciousness itself (questions such as “why is my experience at this particular moment the way that it is?” are never really answered, nor is any method proposed by which they could be answered; the nature of our conscious experiences are treated simply as brute facts). Thus the acceptance of such theories (by those who accept them) is motivated primarily because they explain the intuitive way we think about consciousness. So, provided that we can come up with some theory that explains consciousness without appealing to a non-physical world, we would be thus motivated to reject theories invoking non-physical stuff as providing inferior explanations.*

To start with I must introduce an introductory claim and an introductory definition. The claim I will lean on is the existence of psychophysical parallelism, which says that for any particular physical state of the system there is only one possible associated mental state, even if the mind really is a separate non-physical thing that does not have a causal influence on the physical world. There is not really an argument for this claim, but rather an overwhelming amount of evidence, from fMRIs to brain damage, which points to the existence of such psychophysical parallelism. Which is not to say that questioning the existence of such parallelism is impossible, but rather that the burden of proof is on those who question it to explain why all the evidence points so convincingly to the existence of such a parallelism and to provide some evidence pointing to the absence of such a parallelism.

My introductory definition is much simpler, and probably more contentious. But it is a definition, and so to question it is really to insist that the words in question have a different meaning. With that said the definitional claim is that the physical (observable**) world is causally closed. Of course I have no intent of getting into why exactly this is true by definition, but I will point out that it should seem natural enough when you consider the possibility of something non-physical (non observable) having a causal influence of the physical world. If that were the case we could notice its effects, and then through them observe it, making it part of the physical world after all.

Now consider a theory that proposes that non-physical feature of the world X is responsible for some feature of consciousness. And let us further suppose that Y is some state of the non-physical world that excludes the possibility of X. Now the story involving how we know about he non-physical world is supposed to go something like this: X is in the past. We then form a thought to the effect that “X is the case”, and at the same time our physical brains enter a state corresponding to “X is the case”. But this is insufficient to know that X is the case, as is demonstrated by the following possibility: suppose Y was the case, but the physical world was exactly the same (since the non-physical doesn’t have a causal influence on the physical there is nothing preventing this). Since the physical world is the same our brains still come to be in the state corresponding to “X is the case” and thus by psychophysical parallelism we must be thinking that “X is the case”. Since in both situations we believe that X is the case the fact that we believe that X is the case cannot be evidence for X really being the case. Or, in other words, we can’t know that X is the case. Now some might question this, arguing that the thought that “X is the case” can’t occur without X occurring in the past, and so that this counterfactual setup is impossible. But that is begging the question, because what is under debate here is whether we can know things such as the rules of the non-physical world. Thus we can’t appeal to knowledge about how the non-physical world works in order to justify the claim that we have knowledge about the non-physical world.

This demolishes the ability of theories involving a non-physical world to explain our intuitions and claims about that world. Our intuitions and claims about that world are caused completely by the physical world, and thus can’t give us any information about it, and can be explained without appeal to the non-physical world. This means that even if we somehow established that a non-physical world must exist we would have no way of connecting its features to things like consciousness and the nature of experience, because making those connections would require the ability to have evidence that the non-physical world was actually in a particular state, and then using that knowledge to correlate events in the non-physical world with conscious experience. (Of course there is the hidden premise here that we can’t know anything a priori about the non-physical world, but that is obvious, I would hope, since it looks like it is impossible to know anything a priori.)

* Why the long introduction? Well, I have been thinking a lot recently about the nature of philosophical claims, why we believe them, and how we should decide whether to accept or reject them. So I have turned my argument here into a bit of a test case, showing that we can do philosophy within the model of how philosophy should be done that I am experimenting with.

** Observable here meaning something like: in principle we can have reliable information about it such that it is available to a scientific/experimental study. And naturally what is physical is best defined as that which is in the domain of science.



  1. I can see and predict everything that happens inside my computer by going into Terminal.app and watching the kernel interact with the various processes and devices of the system. If I were to send all this data to another, faster computer I could perfectly predict the actions of this one before they occur. Does this mean that the postulate that there is a part of the computer outside of the software is unnecessary?

    Comment by Carl — June 20, 2007 @ 3:00 am

  2. You can see the processor with your eyes if you open the computer right? Similiarly when we look inside the skull we find the brain. So positing an immaterial mind is about as silly as positing an immaterial CPU that is really controlling the software. How could you know anything about this immaterial CPU?

    Comment by Peter — June 20, 2007 @ 12:53 pm

  3. Yes, but imagine I made an AI that could see and control the contents of my desktop window, communicate with other AIs via the internet, form AI societies, etc. Would such an AI be mistaken for thinking that there is more to the world than software?

    Comment by Carl — June 20, 2007 @ 1:10 pm

  4. Yes, it would be. I am sure I rember writing something previously on why we aren’t justified in thinking that there is some super-reality behind this reality or that we are brains in the vat. The same reasoning implies to such an AI: it can know nothing of this world, it is unjustified in positing its existence.

    Comment by Peter — June 20, 2007 @ 1:13 pm

  5. Re psychophysical parallelism, surely there is no such evidence, and hence no burden of refuting it. Of course physical expressions of mental states are constrained by physical states, but that is hardly sufficient. Re physics being causally closed by definition, how then could there be evidence for such closure (whereas some scientists and philosophers clearly think that there is a lot of evidence for it)? And if not, then (as with parallelism) where is all the evidence for closure? Dualists like myself would expect non-closure to show up only in relatively obscure experiments designed to test the details of an apparently comprehensive theory of the brain, and we have surely not yet go so far in psychology (like as far as Einstein was, in classical physics). And regarding the definition route, suppose (what is surely an epistemic possibility) that God exists, and that he made what he thought of as spiritual as well as physical things (Angels as well as apples) because any definition that would call the former ‘physical’ would surely have presumed too much (i.e. it would surely be circular to use such a definition to conclude that such is not an epistemic possibility).

    Comment by Enigman — June 21, 2007 @ 9:11 am

  6. “psychophysical parallelism” there is so much evidence: see the entire discipline of neuroscience. I mean if you want to ignore it that’s fine by me, but in my book that is an overwhealming abundance of evidence, so much so that not even radical dualists oppose psychophysical parallelism these days.

    causally closed by defintion: just seach for causal closure on this site

    Comment by Peter — June 21, 2007 @ 12:21 pm

  7. I dunno, no one has explained what memory is yet. That should be a pretty big embarrassment to neuroscience. I’m sure they’ll clear it up eventually, but I wouldn’t say that they’ve demonstrated complete causal closure yet. They’ve just shown that if you do stuff to the brain it reliably effects the mind. But we already knew that since eg., drinking alcohol makes you drunk.

    Comment by Carl — June 21, 2007 @ 12:56 pm

  8. I’m not saying its an argument for causal closure (it’s not), but an argument for parallelism (as you agree). Also I have a huge book on my desk entitled “Memory” (right beside the book entitled “Learning”) so I wouldn’t say they haven’t explained it yet, just haven’t finished all their work on it.

    Comment by Peter — June 21, 2007 @ 1:01 pm

  9. I don’t want to ignore what you call “evidence,” I want to know why you call it that, but if you just want to repeat your assertion that it is, and in your defence refer to the large numbers of people who agree with you, then you might resemble other believers (and yet that is surely not evidence that your science is just another faith!), but let’s not reduce our arguments to that level (I’ll stop that now). Your last words are “I wouldn’t say they haven’t explained it yet, just haven’t finished all their work on it,” but that is just it: neuroscientists have not established scientifically closure or parallelism, not if they have details they are still working on (the analogy is always with Newtonian physics, shortly before Einstein, but the point is valid even without any analogies). In ancient India, (substance) dualism was refuted by a sage fasting for a couple of weeks, until even his mind started to go, in that he was unable to recite clearly the sacred texts. But a dualist would say that physical damage to the medium of the mind-body interaction (i.e. to the brain) would of course interfere with our actions. And the associated illness and pain would affect an incarnated mind’s thoughts, feelings, motivations, and other mental activities. Such things do not refute (substance) dualism, not really. You may as well say (as many do) that Galileo refuted modern mathematics, in my opinion. Is it wrong to want proper arguments? To not say that they have been given when popular ones have been?

    Comment by Enigman — June 22, 2007 @ 2:28 am

  10. see most recent post

    Comment by Peter — June 22, 2007 @ 2:30 am

  11. At fish.blogs.nytimes.com Stanley Fish has written some really great pieces about the interplay between faith and reason (or to put it another way, theory and evidence) that deal with a lot of what you’ve been writing about recently Peter. He makes a good point about how interpreting the world is a circular process, but not viciously so.

    I think you can’t read his blog unless you have “Times Select” but you can get it for free if you use a university affiliated email address

    Comment by Carl — June 22, 2007 @ 3:31 am

  12. Thanks for the link, I’ll look into it. (Although I doubt he will change my mind … for the very reasons I pointed out … so problematic.)

    Comment by Peter — June 22, 2007 @ 3:36 am

  13. Thanks (and sorry for going on; if only we could just simply see the truth!)… but what if I believe (having seen previous posts) psychophysical parallelism, at least as far as the evidence indicates, e.g. to 70% credence (given that I know that things like Newtonian theory can be overturned by obsucre and counter-intuitive evidence), and also that I now accept your definitive causal closure, although again only to 70% (given that I know that Kant was premature with his Newtonian definitions). Still I believe your logical deduction from those two premises. It is a good argument, so I believe it to 49%…

    Comment by Enigman — June 23, 2007 @ 2:13 am

  14. Just kidding (my point was that beliefs about parallelism and about closure are not, as was implied above, independent of each other).

    Comment by Enigman — June 25, 2007 @ 6:15 am

  15. I find the term “non-physical” very curious. Can Enigman (a dualist?) or anyone else name one non-physical thing that exists in our universe–and offer meaningful evidence for it? I’m working on a writing project that posits that the nonphysical (aka supernatural) cannot exist within this universe and its laws of physics. All it would take is the proven existence of one nonphysical item/entity to dash my premise.


    Comment by Richard Harkness — July 16, 2007 @ 3:25 pm

  16. Two questions:

    1.) Is love physical?

    2.) Does love exist?

    There are 4 ways to answer them.

    Yes and yes; love is real, but only insofar as it is some property of physical beings, eg. your brain is in the “love” state.

    Yes and no; love isn’t real, strictly speaking. Rather, “love” is just description of a brain state.

    No and yes; love is real, and it’s more than a brain state. Though its existence is typically predicated on the existence of brain states in people, love itself is something different.

    No and no; love is just a concept, and concepts are not strictly speaking real.

    I imagine that materialists will take a mixture of positions 1, 2, and 4. Dualists will appeal to position 3.

    Comment by Carl — July 16, 2007 @ 3:56 pm

  17. Carl,

    Thanks for your thoughtful reply. Here’s my take.

    1) Is love physical?

    Yes: Love exists physically in two locations, externally to the human brain and internally in the brain. Externally only as physical symbols (letters) written or typed on a piece of paper or computer screen, etc. Internally in the brain as a neuronal pathway or collection of neurons tasked with storing and generating the word, as well as the “feeling” called love produced by other brain pathways. The “concept” of love would also exist physically as a neuronal pathway.

    2) Does love exist? Yes, in the ways described above. Love does not exist outside the human brain except as physical letters (symbols) that form the word “love.” Love, anger, jealousy and other human emotions had no existence at all in the universe before sentient beings evolved.

    Many people confuse *abstract* with *nonphysical*. Words/terms can refer to the abstract or concrete. For writers, for example, love is an “abstract” term, while lightbulb is a “concrete” term. Writers attempt to use concrete terms as much as possible (what the novelist John Braine calls “real world referents”). Both concrete terms and abstract terms exist physically in the brain (as described above), but only concrete terms refer to actual things/objects that exist in the outside world (externally to the brain), while abstract terms don’t exist in the external world (except, as noted before, as the physical word/term that’s written or typed, etc).

    An interesting aside: Nouns and verbs reside in separate brain language areas.

    In summary, love is not something nonphysical. I could extend my argument to other abstract terms that are frequently misused such as “energy,” which New Agers mistakenly use in terms such as “psychic energy.” But that’s enough for now.

    Best regards, Richard

    Comment by Richard — July 18, 2007 @ 7:18 pm

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