Friday, January 12, 2018

Grounds for a Sliver of Skepticism

Yesterday, Philosophy Bites released a brief podcast interview of me on skepticism. Listening to the interview now, I feel that I didn't frame my project as well as I might have, so I'll add a few remarks here.

I want to think about what grounds we might have for a non-trivial sliver of radically skeptical doubt.

There is, in my mind, an important difference between, for example, "brain-in-a-vat" skepticism and dream skepticism. Brain-in-a-vat skepticism asks you how you know that genius alien neuroscientists didn't remove your brain last night while you were sleeping, drop it into a vat, and start feeding it stimuli as though you were having a normal day. Dream skepticism asks how you know that you are not currently dreaming. The difference is this: There are no grounds for thinking that there's any but an extremely remote chance that you have been envatted, while there are some reasonable grounds for thinking there's a non-trivial sliver of a chance that you are presently dreaming.

It's crucial here to recognize the role played by theories that are probably wrong. It is, I think, probably wrong that people often have sensory experiences just like waking experiences when they sleep. Dreams are, in my view, always sketchy or even imagistic, rather than quasi-sensory with rich realistic detail. However, I'm hardly certain of this theory, and some prominent dream theorists argue that dream experiences are often highly realistic or even phenomenologically indistinguishable from waking life (e.g. Revonsuo 1995; Hobson, Pace-Schott & Stickgold 2000; Windt 2010). Contingently upon accepting that latter view, it seems to me that I ought to reasonably have some doubt about my current state. Maybe this now is one of those highly realistic dreams.

The idea here is that there are grounds for accepting, as a live possibility, a theoretical view from which it seems to follow that I might be radically wrong about my current situation. I don't prefer that theoretical view; but neither can I reject it with high certainty. It is thus reasonable for me to reserve a non-trivial sliver of doubt about my current wakefulness.

I would argue similarly with respect to two other skeptical possibilities: the idea that we are Artificial Intelligences living in a simulated world, and a somewhat less familiar form of skepticism I call "cosmological skepticism". In both cases, there are grounds, I think, for treating as a live possibility theories that, while probably not correct, would, if correct, imply that you might easily be radically wrong in many of your ordinary beliefs.

In concluding the interview, I also make an empirical conjecture: that seriously entertaining radically skeptical possibilities has the psychological effect of reducing dogmatic self-confidence and increasing tolerance, even regarding non-skeptical possibilities. I hope to more fully explore this in a future post.

Full interview here.

Related papers:

  • 1% Skepticism
  • The Crazyist Metaphysics of Mind
  • Experimental Evidence for the Existence of an External World
  • Zhuangzi's Attitude Toward Language and His Skepticism

    Martin Cooke said...

    It is very philosophical to think that you might be wrong; and I happen to think that you are wrong about the "important difference," that the following is false:

    "There are no grounds for thinking that there's any but an extremely remote chance that you have been envatted,"

    Were there such aliens, they would use their enormous powers to remain unknown to us. And they would also have guided our world so that it was the way they wanted it to be. Normal life would seem to make the chance of them very low, but that chance would really be higher. What, then, is the chance of our being in such a universe. I don't think that it can be very low, because of the Fermi paradox. Why not say that it is unlikely to be lower than 1%?

    Eric Schwitzgebel said...

    Thanks for the comment, Martin!

    The mere hypothetical "Were there such aliens..." wouldn't be grounds. But if the reasoning starts with the Fermi paradox (and maybe it does), then conceivably one could make a grounds-based case. The Fermi paradox gives us grounds for Live-theory X. Live-theory X yields a significant chance that we are envatted. But I'm not seeing why the Fermi paradox would yield a live theory with envatment as a likely consequence. The wilder theories, like the Zoo hypothesis still don't seem to yield envatment as likely.

    Anyhow, that's the structure as I see it -- the general difference between grounded and ungrounded radically skeptical hypotheses.

    G. Randolph Mayes said...

    Eric, I've used your 1% paper a couple of times now and epistemology students have responded well to it. When I talk about the difference between BIV skepticism and dream (or Sim or Boltzmann brain skepticism) I also emphasize that it isn't only that the latter two are more probable. It's also that on a certain conception of rationality it is reasonable take them seriously, where it is not reasonable to take BIV skepticism seriously. That would be a pragmatic/ conservative/ anti-foundationalist account according to which it is rationally permissible to believe whatever you currently believe (i.e., maintain your current credences) until you have been exposed to some evidence against it. There is no evidence at all that today's scientists can create BIV's; at best it just seems like something that could be done in a remote future. In other words, to insist that the BIV skepticism rates serious empirical consideration, you have to be something close to a Cartesian foundationalist.

    Martin Cooke said...

    Yeah, the devil's in the details; thanks :-D

    Eric Schwitzgebel said...

    Hi Randy --

    Yes, that seems right to me. Something like the pragmatic/conservative/anti-foundationalist view you express is, I think, partly behind my greater interest in "grounded" skeptical scenarios than ungrounded what-ifs.

    Eric Schwitzgebel said...

    Martin: Yes, I do think the details matter! Part of grounded doubt is trying to assess whether you're compounding moderately plausible things as opposed to things sufficiently remote that you really ought to end up somewhere under 0.001% credence.

    Toby said...

    Just a thought. My experiences of dreams align with yours: they are rarely if ever similar to waking conscious experience, instead being usually fragmentary, inconsistent and odd. But it also seems that my dreaming self is usually unable to reason from that observation to the conclusion “therefore this is probably a dream”. I remember frequently feeling confident that I’m not dreaming, or not having the possibility occur to me, even in the middle of bizarre experiences that are (with hindsight) obviously dreamlike. So, while it may not be the case that my dreams are consciousness-like, it may be the case that my present experiences aren’t consciousness-like either; I just haven’t noticed that fact. If so, should this increase my credence in the skeptical hypothesis?

    Anonymous said...

    "that seriously entertaining radically skeptical possibilities has the psychological effect of reducing dogmatic self-confidence and increasing tolerance, even regarding non-skeptical possibilities" if seriously entertaining radically skeptical possibilities means something more or less akin to the usual academic procedures than I doubt this is true, in part b/c of the differences between knowing about and knowing how.

    Callan S. said...

    It's ironic, as what practical outcome is there from considering oneself is in a dream? What are you going to do about it?

    The irony part being, that's exactly the sort of thing you'd expect from a dream. Doing things for inexplicable reasons.

    Yohan said...

    Professor Schwitzgebel, I was wondering if you have written elsewhere about your understanding of terms like 'possibly', 'probably', 'almost certainly' and so on. Do you subscribe to a subjective interpretation of probability? And if so, which arguments in favor if it worked best. Dutch books? 'Consistency'?

    I'm a neuroscientist and an old-school frequentist, so I have trouble with the idea of assigning numbers or degrees to doxastic states -- particularly states for which there is no behavioral test for whether these numbers/degrees are accurate.

    Since I've always found you writings clear and accessible, I was wondering if you've thought about these issues. Searching your blog through google hasn't really turned up anything directly related. (The Boltzmann Brain post is sort of related, but my first thought was to wonder why the idea of the 'identity of indiscernibles' did not crop up.)

    Eric Schwitzgebel said...

    Thanks for the comment, Yohan!

    On identity of indiscernibles: I haven't written about this yet, but I think it probably buys less than people might want, since arbitrarily closely similar things might still be different in some minor way (a googleth of a Planck length? an indexing number in the mind of God?)

    Back in the old days of grad school (early 1990s) I was interested in probability and Bayesian modeling, but I ended up going different directions. One result of my earlier thinking is to be nervous about any approach to probability or confidence that aspires to being the universally right answer -- whether frequentist, Bayesian, whatever. All the models seem(ed) to me to lead to paradox and trouble if taken in too totalizing a way. So in my work on low-confidence skepticism, I use the percentages as a rough measure of confidence or hypothetical rationally betting, but I specifically prefer to disavow a strict reading of these are numerically precise credences (see my paper "1% Skepticism" in Nous 2017).