Thursday, October 1, 2009

Skepticism and Normativity

Thinking you have figured out how to solve age old philosophical problems, very quickly, is generally a bad sign.

Nonetheless, ever since TFing Intro Epistemology last semester, I find myself feeling more and more that worries about external world/other minds/memory skepticism involve an incoherent melange of a sharp proof theoretic question, together with a fuzzy normative question.

The proof theoretic question is something like:
- Can you prove the external worlds exist, starting from premises that contain only necessary truths?
- Can you prove memory is reliable starting from premises containing only necessary truths and true statements about current experience?
[Where "prove" can be cashed out in various formal ways - e.g. first order logic, or modal logic, or intuitionistic logic - to yield different variants of the question.]

And the normative question is:
When is it empistemically OK to assume premises in a given set X, given that I cannot prove them (in logic L) from premises in set Y?

Once we've made this distinction, and noted that some premises which one might assume are true, and others false, the normative question looses much of its interest (at least for me).

Furthermore, we can point out to the skeptic who e.g. believes in the reality of past experiences but not in the external world, that his position appears exactly analogous to our own. We can challenge the skeptic to provide any kind of distinction between what's OK to assume vs. not OK to assume that looks remotely principled enough to motivate our revising our judgments on the subject.

"In what sense," we can say to the skeptic, "do you know that e.g. there are infinitely many primes, or that it's impossible to know things about the external world, such that I don't also (by those very same standards) count as knowing that I have a hand?. In both cases, there are more radical skeptics whom we cannot persuade. Thus, in saying that you know, but I do not, you seem to be just stomping your foot and making the unmotivated value judgment that it's OK to assume what you assume and not OK to assume what I assume.

Why should I be more confident that you have correct moral beliefs about what it's OK to assume, than that I have correct descriptive beliefs about whether I have a hand?"


  1. Now I'm not sure whether you said that in a confusing fashion or I think you're radically wrong but it's one of the two.

    I mean for starters why should you believe that acceptable epistemic inferences can be captured in anything we would intuitively consider a formal system? I mean sure you can always simply *define* a 'formal' logic to merely be the set of inferences that are authorized but that doesn't solve anything. Hell, one could even have the view that a rigorous formal system could never express the concepts we are interested in much less capture acceptable reasoning about them.

    On the other hand saying that you've 'reduced' the problem of epistemology to the fuzzy normative question of what is ok to assume/use doesn't seem like much of a reduction at all. I mean how is this different from simply saying "epistemology is reduceable to the fuzzy normative question question of 'when is it ok to infer a proposition'"? As long as you think there is some kind of fact of the matter about whether certain kinds of assumptions/inferences are normatively ok epistemology poses deep compelling questions.

    However, I think the correct resolution to virtually every foundational epistemic question is simply to deny that there is any such thing as a fact of the matter as to whether it's 'ok' to assume/infer something. I mean as a matter of fact we do draw certain conclusions and not others. Also there are facts about which kinds of reasoning have tended to yield poor results and which have good track records. There are also facts about what you can prove about various reasoning techniques under various axiom schemes, e.g., if we assume the observed events can be modeled as a sequence of 0's and 1's obeying such and such property then so and so inferential strategies have blah property. However, these kinds of 'boring' facts simply exhaust what there is to same about inference.

    To put the point another way: You wouldn't suppose there was a fact about what answer a hunk of silicon should output when given a certain input, only facts about what the designer intended, what standard engineering/physics principles predict, and what you find surprising. I mean imagine saying, "sure when I input +5V, 0V, +5, +5, +5 volts on pins 1-5 this chip outputs +5V on pin 6 just like the spec says but the RIGHT answer to +5V, 0V, +5, +5, +5 volts is +5V." That would be silly. The only reason we imagine foundational questions in epistemology are any different is that it's very hard to think of our own language as nothing but physical input/output patterns.

  2. The point at the last paragraph is pretty close to what I am trying to say.

    People do reason in various ways, and we can say that some of these ways are necessarily truth preserving, others or not etc.

    We can also ask whether, for one given formal characterization of a way that people reason, this method of reasoning can be used to generate a given conclusion.

    These are both purely descriptive questions, and not what is at stake in epistemology as traditionally understood.

    Then, in addition to this, we have the normative question - which of the truth preserving formal procedures is it epistemically "OK" or "good" to use?

    Here, we could either say there is no fact of the matter (as you seem to say) and abandon the notion of justification, or look to normal usage for what kinds of valid reasoning procedures typically get classed as OK (e.g. assuming 2+2=4 is OK, assuming the 4 color theorem is not).

    I was presenting things as per the latter strategy, but I don't think much hangs on the difference. Maybe it's useful to have a word for the property of believing that P + being able to argue for P using only true premises and truth-preserving inference methods, which every adult, developmentally normal human finds obvious.