JPK: S’s belief is justified iff S has a possible counterpart, alike to S in all relevant intrinsic respects, whose corresponding belief is knowledge.One of the moves I often use in that paper involves an exploitation of content externalism. My belief is justified if my intrinsically identical counterpart's is knowledge -- but his knowledge needn't have the same content as my justified belief.
When I presented this paper in St Andrews last summer, Jessica Brown expressed the worry that the kind of externalism I was relying on made the view too liberal. She was worried that there'd be cases of intuitively unjustified beliefs, even though there were intrinsically identical counterparts who had knowledge. One possible family of such cases involves 'slow switch' subjects -- people who change in their external environments in a way that implies a change in content, without realizing it. Suppose someone commits the fallacy of equivocation because she has been slow-switched; won't JPK have the implication that her resultant belief is justified anyway? I think that JPK probably will have this implication. But I don't think it's intuitively the wrong one. Consider a case. This example is borrowed from Jessica's book.
Sally starts out a regular earth-person, who knows some stuff about aluminum, but not much detail about its chemical composition. She does know, however, that some of it is mined in Australia, so she says to herself:
(1) Aluminum is mined in Australia.
One night, unbeknownst to Sally, she is moved to Twin Earth, where there is no aluminum, but instead, some superficially similar stuff twaluminum. After a while there, Sally has thoughts about twaluminum. In particular, she comes to know that some of it is mined in the Soviet Union. This is the belief she expresses when she says to herself:
(2) Aluminum is mined in the Soviet Union.
She hasn't forgotten her previous knowledge, so she still knows (1). And she's unaware that "aluminum" in (1) refers to different stuff than does "aluminum" in (2). So she might well put these together and infer her way to a claim she'd express by:
(3) Something is mined in Australia and the Soviet Union.
Sally equivocates on "aluminum", because of her external environment. Intrinsically, she's just like her counterpart who stays on regular earth and comes to know that aluminum is mined in both places, and (validly) concludes that something is mined in both places. So JPK has it that Sally's conclusion, (3), expresses knowledge, even though it is the product of equivocation.
I think, however, that this is exactly the right result. It is intuitively plausible to suppose that Sally's appearances are misleading, but her belief is justified. This mean that invalid reasoning doesn't always interfere with the justification of beliefs. But that's what we should think about this case, independently of JPK.
I'd be interested to hear any thoughts from any readers, but especially answers to these:
(a) Do you agree that it is intuitive to describe Sally's conclusion (3) as justified?
(b) Do you see any other, more problematic implications for JPK that derive from slow-switch considerations?