Wednesday, May 23, 2007

Surprisingly Common Sense

Because of my common sense, I know, as I type this, that I have hands; but presumably a disembodied, and therefore handless, brain-in-a-vat might think so too, as a result of its experiences being so arranged that they resembled mine, down to the smallest detail—so, perhaps I am such a brain-in-a-vat? My problem is that if I do not know that that is very unlikely (or impossible)—and how could I examine its likelihood?—then I can hardly justify my belief that I have hands; so I would not know (for sure) that my hands exist. That is a problem because one naturally feels that one’s confidence in such everyday propositions is fully justified, somehow.
...... But therefore we have G E Moore’s common sense refutation of such Cartesian scepticism (and Humean scepticism can be treated similarly, e.g. see my A Pair of ‘Sceptical’s): All such stupefying scenarios can be known to be impossible because one really can know that one’s hands (knees, feet etc.) certainly do exist. That is an almost complete refutation—only a scientific question remains. Sceptical scenarios are seemingly rational possibilities that are not made sufficiently unlikely by the empirical evidence, whence even when we are not tempted by the scepticism, they naturally raise such scientific questions as: How do we know that we have hands?
...... Insofar as we think of our knowledge of the external world as being constructed indirectly, from nerve-signals coming from sensory organs external to our brains, it is quite mysterious (in view of such sceptical scenarios) how our natural confidence in our knowledge of the ordinary things around could be justified. Nonetheless the foundations of our scientific knowledge are surely our common sense certainties (e.g. as we perform experiments), so we cannot really question them, we can only seek their scientific justification. Now, scientific questions require scientific answers and of course, as a philosopher of mathematics I don’t have a scientific answer, but what I can do is speculate.
...... The scientific answer would surely be some theory devised to account for scientific observations of the relevant phenomena, so we might ask ourselves: What would be relevant here? Well, in what ways might we become directly acquainted with things? A clue comes, it seems to me, from our need to explain the direct mind-brain interaction (since something else that is common sense is Cartesian dualism), because quantum mechanics is likely to be a key component of that explanation. If so, then (wavefunctions being spread out) we might expect direct knowledge of external objects to be possible too, and so the relevant phenomena could well include the micro-psychokinetic (the ‘micro’ means that the mind interacts directly with chance phenomena in the external world, i.e. not levitation).
...... Of course, common sense also tells us that the paranormal is not worth investigating. After all, such things are investigated, by reputable sceptics and by believers, and nothing ever comes of it. But then, a socio-economic explanation for that might involve that word ‘reputable’—I don’t want to delve into such issues here because they are intrinsically complicated (as political issues are). I’ll just observe that if I’m right (and why not?) then the paranormal would, insofar as it occurs, be the extremity of something quite normal (much as superfluids are), varying in the usual way of such biological things (and insofar as it does not occur—e.g. poltergeists—its plausibility could be similarly explained, i.e. via the ubiquity of something that is both obscure and like the fiction). After all, the empirical evidence is not inconsistent with lesser degrees of the so-called sixth sense being surprisingly common (e.g. consider the sense of being stared at, which would probably have been selected for if our underlying physics does allow it; cf. this recent research).
...... Just as Humean scepticism motivates our taking seriously what is common sense, that there are laws of nature (indicated by the correlations due to them), by verging upon a reductio of their non-existence (of there being only the correlations), so Cartesian scepticism motivates our taking seriously what is common sense, that we are directly acquainted with such natural kinds as hands (e.g. via a process akin to the mind-brain interaction), by verging upon a reductio of its non-existence (of our having only an indirect acquaintance with our own hands).


SamD said...

So if I have this right (and please excuse the gross oversimplification I'm about to indulge in), you are arguing that we can know that we are not BIV's because our minds directly interact with the external world. Since the BIV scenario is only possible if the relationship is indirect, your argument would rule out it's possibility.

Am I on the right track?

Enigman said...

Hi samd, it's nice to be communicating rather than soliloquising, so I'd excuse a lot, but I don't think you've oversimplified so much as clarified, and so pointed out a potential problem for my view: Even in a BIV scenario one would be interacting directly with an external world. (Is that where your track was leading?) My observation (at such a point) would be that there are two possibilities (at the ends of a continuum of fuzzy possibilities), either one is recently envatted (in which case one might concentrate upon the external object in question, and fail to tell by one's direct acquaintance with it that it was real, whereas one might succeed if it was real) or else one is not (in which case one's 'real' would be the envatter's 'virtual' and that just resembles our ignorance of the inner nature of things).

Enigman said...

(I wish I hadn't used so much bold now, as it looks like shouting!) Anyway, maybe I missed your point. My argument does not rule out the possibility of a BIV scenario, it only argues against our not being able to know that we are not in a BIV scenario when we are not in one. So more clearly, I can imagine that my brain (as it is now, outside of a BIV scenario) is removed and put into a superior alien machine, and that I then try (as I just did) to check the reality of the world around me, and that I fail to discover (as just then I did not) that it is indeed real.

SamD said...

Ouch, so many negatives in the one sentence!

I think you were closer to what I was thinking in the second reply

So we can know that we are not in a BIV scenario when we are not a BIV. This is presumably based on a direct (body/environment)/(body/mind) type relationship. But if the envatted fails to discover that the world around them is real, (which logically they must), does it necessarily follow that they do discover that the world around them is not real?

If the envatted has a direct relationship to their simulated body, so that they exist in a direct relationship similar to the one I described above except that the body and environment are simulations, then plausibly they could not discover that their world was not real. For myself, being able to make this discovery (or not) is the fundamental issue in settling BIV related scepticism.

This possibility is why I think your first reply, even though it's not what I meant, has something to it.

Enigman said...

I've found it useful (as I reason via analogies) to think about how we can be so sure about simple arithmetic, even though we do know that we do make mistakes with it: We can become justifiably confident about elementary arithmetic simply by running through the calculations carefully enough, even though if we were drunk we might make a mistake and be mistakenly confident that we were right. (What we could not discover so easily is the underlying nature of the natural numbers.) The idea is that one tries to make some careful checks and then, by reflecting upon the manner of one's success, one is able to deduce (cf. G.E. Moore) that one is not so drunk. (And even a drunk might be dimly aware of a lost ability to calculate accurately; maybe not on their first ever drinking spree, but they would be unlikely to try to make such careful checks then anyway, in my experience:)