Argument for dualism

In PHIL 4410 yesterday, I offered Descartes’s argument for dualism:

1. Anything that we can legitimately conceive is logically possible.
2. We can legitimately conceive being conscious without having a brain that’s doing anything. (We can imagine being a disembodied consciousness.)
3. So, it is logically possible to be conscious without having a brain that is doing anything.
4. For any X and Y, if X can exist without Y, then X is not identical with Y.
5. Therefore, consciousness is not identical with having a brain that is doing anything.

It’s an interesting argument, since the premises look pretty plausible. Any thoughts? Where does the argument go wrong?

Here’s another item to consider. Can the same argument be used to show that, say, a computer operating system like Windows is not identical with a computer doing anything? Can we legitimately conceive Windows existing in a world devoid of computers? Or is consciousness seemingly different from a computer operating system in this regard?

(I raise this last point because I often like to compare human consciousness to an operating system: the mind is the software, and the brain is the hardware, and the software is somehow present in the organization and functioning of the hardware, and can’t exist without it. I’m wondering whether this argument points out an important flaw in my comparison.)


8 thoughts on “Argument for dualism

  1. Rolfe Schmidt

    I’m not sure what it means to “legitimately conceive” something, but if the definition is so narrow that (1) holds then I think many of our conceptions are illegitimate. We can hold ideas in our mind without understanding the infinite chains of deductions which follow from those ideas. It is easy to imagine feeling comfortable with a set of ideas that are in fact contradictory and hence illegitimate (at least if we accept (1)).

    Because I think that (1) implies such a strong notion of legitimate conception I am uncomfortable with (2) and I think it needs much more argument. The fact that I can imagine something does not make it legitimate. So I don’t accept (3) without justification of (2). I happen to think that will be tricky, but would enjoy being convinced otherwise.

    Finally, for conclusion (5) I think it is important to emphasize that even if I accept the rest of the argument we still have not shown that our consciousness exists without our brains doing something.

    Re: the windows question, my knee-jerk reaction is to say that if the computer-free copy of windows is interacting with the physical world, then it can be thought of as a natural object that obeys complex laws that can be used to perform computation. In the extreme case where we say that we have a version of windows that interacts with the physical world but which cannot be decomposed into anything more basic, I’d just say we’ve found a new elementary particle that obeys very odd laws. Just like an electron “computes” its response to its environment, this computer-free copy of windows computes its response to whatever input it receives.

    If a computer is just a physical system that can perform computations, we still have a computer. I can certainly imagine windows existing without our silicon chips and spinning drives.


  2. Huenemann Post author

    I agree that I’m not sure of #1 — though I don’t have a much better method for figuring out what’s logically possible. And I’m growing increasingly sure that #2 is just false. Consciousness may have everything to do with being part of a complex information processor, and I don’t think we can conceive an immaterial (let alone immaterial and indivisible) one of those.


  3. Rolfe Schmidt

    I don’t hold out much hope for figuring out what is logically possible in general, usually it is only clear when something is logically impossible. I think it is very useful to think about the class of logically possible things, just difficult to determine membership. It seems like a much harder version of the troubles Goedel found.

    My problem with #1 is that I think “legitimately conceive” should be weaker than logical possibility, and that we should be able to feel comfortable that our conceptions are legitimate. This means I would allow for concepts to be legitimate but logically impossible. This sounds like a problem but it is unavoidable if “legitimate conception” is something we can grasp.

    Science gives a good example of how I think we can have legitimate concepts that are not logically possible. Most every scientific theory is either poorly defined or wrong in some sense, but I still think it is legitimate to accept the best theories of the day.

    After all of that rambling, I think your question is key: can we conceive an immaterial information processor? I agree with you and say no. If we conceive it without conceiving the material details, it just means our concept is not complete.

    Here’s my problem with conciousness: at what point does that information processor “experience” something?


    1. sandiatwood

      Responding to your comment: “My problem with #1 is that I think “legitimately conceive” should be weaker than logical possibility, and that we should be able to feel comfortable that our conceptions are legitimate.”

      In “On the Amendment of the Intellect” Spinoza makes an interesting argument in defense of legitimate conception as the highest mode of perception and logical possibility as a weaker mode…


      [19] (1) Reflection shows that all modes of perception or knowledge may be reduced to four:—I. (2) Perception arising from hearsay or from some sign which everyone may name as he please.

      II. (3) Perception arising from mere experience—that is, form experience not yet classified by the intellect, and only so called because the given event has happened to take place, and we have no contradictory fact to set against it, so that it therefore remains unassailed in our minds.

      III. (19:4) Perception arising when the essence of one thing is inferred from another thing, but not adequately; this comes when [f] from some effect we gather its cause, or when it is inferred from some general proposition that some property is always present.

      IV. (5) Lastly, there is the perception arising when a thing is perceived solely through its essence, or through the knowledge of its proximate cause.


  4. Huenemann Post author

    I guess there could be a scientific theory that turns out to be extremely useful but logically impossible — maybe some weird but possible application of it would yield a contradiction, or maybe there’s some little detail which is problemmatic. I’m surprised you think this happens often in science (maybe it does; I’m not in a position to know). And I’d like to think that every useful theory could be carefully reformulated so as to be at least logically possible, but maybe that’s an illegitimate wish!

    And, yes, I share the worry over (what I call) “the problem of emergence” — how mental properties emerge out of information processing. The best explanation I’ve seen offered is Dennett’s, in Consciousness Explained — but admittedly, that works only by watering down the explanadum (conscious qualia) to a level at which it might be understood as mere “judgment that,” and it sure seems there’s more to subjective experience than making judgments about our environment!


  5. Rolfe Schmidt

    I wrote that comment too quickly. I didn’t mean to imply that most scientific theories were logically impossible — I think the opposite is true. I meant to make a much weaker statement that most scientific theories are physically wrong — if pushed too far, the theories will be found to imply false statements about our world. Newtonian Mechanics is a good example.

    When we find these problems, we quickly modify the theory to steer clear of the failures or discard it for a new theory. But you never know what will turn up tomorrow. Still, I think it is legitimate to accept a well tested theory.

    I’m not claiming that scientific theories must always be wrong — perhaps we’ll have an accurate theory of everything one day — but I think they are often wrong. I also think that theories that simplify complex phenomena will probably always need refinement.

    For full disclosure, my background is mostly in Math and Physics, so that shapes my perspective a bit.

    I’ll have to read Dennett. I’m working my way through Chalmers’ The Conscious Mind right now and that is my first exposure to the field.


  6. Sandi

    I am not a techy person, don’t really understand it honestly but…did not the idea of software inspire the creation of hardware. What if hardware simply provided a particular and useful application of an already existing software.



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