- Jason works at Yale but I don't know that Jason works at Yale
- Jason works at Yale but it's not certain that Jason works at Yale
Jason thinks that knowledge doesn't entail certainty, and so a knowledge norm of assertion can't explain what's wrong with assertions of (2). Instead, he opts for a certainty norm of assertion, that's meant to explain both.
The argument I thought I remembered from the paper was that the certainty norm was strictly stronger than the knowledge norm. The certainty norm explains (2) in the obvious way (just like the knowledge norm explained (1)); and it explains (1) by invoking the entailment of knowledge by certainty. If I don't know that Jason works at Yale, it's not certain, so I can't assert the first conjunct. But today I read the paper again, and that's definitely not the argument. Certainty, in the sense Jason discusses, does not entail knowledge.
The relevant notion of certainty here is 'epistemic certainty', according to which 'one is certain of a proposition p if and only if one knows that p (or is in a position to know that p) on the basis of evidence that gives one the highest degree of justification for one's belief that p'. (p. 35) Since certainty does not entail knowledge, on Jason's view, it is not quite clear to me how a certainty norm explains the infelicity of (1). Of course one can't know both conjuncts in (1), but I don't see why why one couldn't have certainty in both conjuncts. Here is Jason's attempt to deal with the issue:
Consider the proposition that there are no large Jewish elephants in my bedroom. This may have been an epistemic certainty for me five minutes ago, even though I did not know that there were no large Jewish elephants in my bedroom. I did not know that there were no large Jewish elephants in my bedroom, because I did not believe it, and I did not believe it simply because it didn't occur to me ever to entertain that possibility. Nevertheless, in this case, if I had entertained the propsition that there are no large Jewish elephants in my bedroom, I would have known it. The reason this counterfactual is true is because it is an epistemic certainty for me that there are no large Jewish elephants in my bedroom. So the fact that a proposition is an epistemic certainty for a person does not entail that the person knows that proposition. If a proposition is an epistemic certainty for a person at a time, then it does follow that the person is in a *position to know* that proposition. Being in a position to know a proposition is to be disposed to acquire the knowledge that the proposition is true, when one entertains it on the right evidential basis. Since epistemic certainty entails possession of this dispositional property, utterances [like (1)] are odd. (p. 49)
The thought seems to be that if something is certain, then if one asserts it, one must know it. But it doesn't follow from his explanations of these notions that this must be so—couldn't something be asserted without being entertained on the right evidential basis? Suppose for instance that p is certain for me, but I don't know p because I am ignoring my overwhelming evidence for p, and basing my belief that p on some bad evidence. Couldn't it be, in this case, that it's also certain for me that I don't know p? I think it seems plausible that I might—my evidence, which, suppose, includes some sort of introspective access to the source of my belief—might overwhelmingly establish that I don't know that p. But if so, the certainty norm predicts that 'p but I don't know that p' should be assertable.