| One of the most fundamental problems afflicting externalist theories of epistemic justification is that, on such views, knowledge turns out to be compatible with objectionable forms of subjective irrationality. This has led many externalists to include what might be called a no-doxastic-defeater requirement in their epistemological theories. After examining several of these views and showing that each is unsatisfactory, I advance my own view of doxastic defeaters. I then argue that even with a requirement of this sort, there is still an important kind of subjective irrationality which is incompatible with knowledge, one which involves what a subject ought to do or ought to believe. This leads to the development and defense of what I call a no-normative-defeater requirement. I then discuss the consequences that these kinds of defeaters have for the debate between internalism and externalism, arguing that even though an externalist condition is necessary for knowledge, the two aforementioned requirements capture what is important about internalism by securing a crucial role for subjective rationality, evidence, and epistemic responsibility in the acquisition of knowledge. Finally, I apply these considerations to some central debates regarding testimonial knowledge. I examine the widely accepted view that speaker-knowledge is a necessary condition for testimonial knowledge. In particular, I consider the following thesis: [TK] For every speaker, S, and hearer, H, if H comes to know that p via S's testifying that p, then S must know that p. I then argue that, because doxastic and normative defeaters are not necessarily transmitted via testimony, a speaker, S, can have a defeater for her belief that p which is not transferred to her hearer, H; accordingly, S fails to know that p and yet H can nonetheless acquire knowledge that p on the basis of S's testimony. Thus, I show that the dominant view of testimonial knowledge, i.e., [TK], is false. I then provide an alternative framework for understanding testimonial knowledge. |
