Tonight [post delayed due to maintenance on CD] in my fallibilism seminar, we discussed Charity Anderson’s forthcoming paper, “Fallibilism and the Flexibility of Epistemic Modals.” It’s a really great paper, though written from a diametrically opposed view as my own (well, not entirely, since she does say that Concessive Knowledge Attributions are expressions of fallibilism, which now seems to be a majority view —Lewis, Dougherty, Rysiew, Littlejohn, Anderson–over against Stanley 2005). She offers a model of a shifting modal base for epistemics to relieve tension between fallibilism and the Knowledge-might principle
Know-Might Principle (KM): If S knows p, then ‘it might be that ~p’ is false for S
Here are a few reflections about how a Jeffreyan radical probabilist like me will think about the issues.
1. First, it seems really, really odd to me that someone who *endorses* fallibilism as the thesis that “knowledge is compatible with a chance of error” *also* endorses KM. For, it seems obvious to me, if, in the relevant usage, there is a chance that not-p, then not p is a possibility. So that’s something I just don’t get. I understand motivations for infallibilism. It’s an attractive view in many ways (when wedded to a slick error theory). But I don’t understand the impetus of so many to give fallibiism with one hand and take it away with another.
2. Her basic idea is that—assuming the standard account of epistemic possibility (yuck!)–not only does the relevant domain of knowledge change from person to person, the modal base changes from one time to another for an individual.
For example, when someone says
(*) Sure, it could be a painted mule, but I know it’s not
what’s going on is that the modal base is not the speaker’s total evidence, but a proper subset of it, specifically, lacking that it is a zebra. Shifty modal bases strike me as waaaay too much machinery for the problem, like swatting a fly with a sledgehammer, when we can explain the data by a probabilistic account of epistemic possibility—<e>p iff Pr(p) > 0. But there’s another oddity here.
Because of the nature of epistemic support relations, if you have all of the support for p, you have all of the support for all p supported. So when someone makes a CKA—Kp & <e>~p–, taking p out of the picture isn’t enough, for that leaves in all the epistemic support for p, and so is consistent with K-level J that p, and that’s doing all the work (Kp is, as it were, a mere puppet: the E for p is the hand). So you’d have to take out all the E for p as well (or face the seemingly insurmountable problem of drawing some non-arbitrary line), and that’s just…well, weird. And it seems a really drastic maneuver bound to cause problems.
While I was going on about what problems this would cause and the arbitrariness involved, Chris Tweedt and Allie Thornton pointed out that I had misread her view. I was assuming the evidence base shifted between the first conjunct of the CKA and the second. Chris pointed out the passage where this is clearly not what she is saying: “for many propositions we know, there is some body of propositions, Kp, such that we can know p on the basis of K-p even though ‘might ~p’ is true relative to K-p.” I had rolled right over this, having heard the paper given as a talk. But the first conjunct of the CKA—“Kp”—is evaluated on the same evidence base as the second conjunct—“<e>~p”—and the latter requires subtracting not just p, but all the evidence for p, then clearly the first conjunct won’t be true, and no harmony has been shown between CKA’s and KM.
Well, the guy is stacking the bar stools now and the other guy is mopping the floor, so I guess other points will have to wait. This is a very thought-provoking paper which anyone interested in epistemic modals should read.