The challenge Duncan considers in this section is that Moorean assertions like "I know I'm not a brain in a vat" seem conversationally inappropriate. As he puts it earlier in the book,
[T]here appears to be something conversationally very odd about asserting that one knows the denial of a specific radical sceptical hypothesis. That is, even if one is willing to grant with the neo-Moorean that one can indeed know that one is not, say, a BIV, it still needs to be explained why any explicit claim to know that one is not a BIV (i.e., 'I know that I am not a BIV') sounds so conversationally inappropriate. Call this the conversational impropriety objection. (115)The answer Duncan gives to this challenge in §8 ("Knowing and Saying That One Knows") is that the Moorean claims in question, in the contexts under consideration, generate false conversational implicatures to the effect that one has the relevant discriminatory abilities:
[I]n entering an explicit knowledge claim in response to a challenge involving a specific error-possibility one is not only representing oneself as having stronger reflective accessible grounds in support of that assertion than would (normally) be required in order to simply assert the target proposition, but also usually representing oneself as being in possession of reflectively accessible grounds which speak specifically to the error-possibility raised. (142)I tend to be suspicious of pragmatic explanations for infelicity that don't come along with systematic explanations. Grice tells nice stories about how his maxims predict particular implicatures, given various contents asserted. What is Duncan's explanation for why first-person knowledge assertions implicate that one has the perceptual capacity to discriminate the state of affairs claimed to be known from alternatives that have been mentioned? Let's take an example, adapted from one of Duncan's (p. 146 -- one of his "unmotivated specific challenge" cases):
- Zula: [looking at some zebras in the zoo] There are some zebras over there.
- Asshole: They look like zebras. But who knows? Maybe they're cleverly disguised mules.
- Zula: I know that they're zebras.
Duncan's view is that Zula last utterance is true but unassertable—unassertable because it implicates falsely that Zula can discriminate perceptually between zebras and cleverly disguised mules. But why does it implicate that, if it doesn't entail it? I can't see how any of Grice's maxim's would generate the implicature in this case. Without some kind of story about where the implicature comes from, the suggestion that any impropriety comes down to pragmatics looks suspiciously ad hoc.
Notice also that certain predictions of the pragmatic explanation do not seem to be borne out. Since Duncan's story depends essentially on the implicatures involved in Zula's assertion, it does not extend to knowledge attributions that Zula doesn't assert. For example, it does not extend to Zula's unasserted thought in this case:
- Zula: [looking at some zebras in the zoo] There are some zebras over there.
- Asshole: They look like zebras. But who knows? Maybe they're cleverly disguised mules.
- Zula: [thinking to herself] What an asshole. I know that they're zebras.
Zula's thought won't mislead Asshole or anybody else, so Duncan's story can't show why it's inappropriate. But it seems intuitively problematic in the same way her original assertion is. Similarly, there seems to be impropriety about Moorean assertions in third-personal contexts where one won't mislead. Suppose that you and I know full well that Zula can't tell the difference between a real zebra and a fake zebra; we also know full well that she is looking at a real zebra right now. Consider this:
- Zula: [looking at some zebras in the zoo] There are some zebras over there.
- Asshole: They look like zebras. But who knows? Maybe they're cleverly disguised mules.
- Me: [to you, out of earshot of Z and A] Zula knows that they're zebras.
My assertion seems problematic in the same way Zula's original one does; but I do not mislead anyone. (We could also consider, for this point, a version of the first-personal case where it is stipulated to be common knowledge that Zula lacks the discriminatory ability in question.)
Here is one more observation about the case. Suppose nobody says anything about knowledge, as in this variant:
- Zula: [looking at some zebras in the zoo] There are some zebras over there.
- Asshole: They look like zebras. But maybe they're cleverly disguised mules.
- Zula: They are zebras.
Insofar as I can feel the force of Duncan's suggestion that Zula's original final utterance—'I know that they're zebras—implicates that she has special abilities to rule out fakes, I think the same applies here. But if so, I think that this may show that even if Duncan has identified something wrong with the knowledge assertion, he hasn't identified everything wrong with it. For we have no inclination whatsoever to think that Zula speaks falsely in asserting, even in the face of the skeptical challenge, that there are zebras. The case is very different for her self-ascription of knowledge. The intuition is not merely that she shouldn't say she has knowledge; it's that she doesn't. (Indeed, I think the intuition is that it'd be fine for her to assert that she doesn't have knowledge.) Since there seems to be a special phenomenon about knowledge ascriptions, the pragmatic story will only work if it is particular to knowledge ascriptions. But I don't think it is; once the challenge has been made, an outright assertion of the proposition that was challenged does—so far as I can tell, in exactly the same way a bare knowledge ascription does—in some sense convey that one has the ability to answer the challenge.
More thoughts on more central elements of Duncan's very interesting book to follow. I started here for the simple reason that it was freshest in my mind when I finished the book today.