Dan O'brien

One kind of successful communication involves the transmission of knowledge from speaker to hearer. Such testimonial knowledge transmission is usually seen as conforming to three widely held epistemological approaches: reliabilism, impartialism and evidentialism. First, a speaker must be a reliable testifier in order that she transmits knowledge, and reliability is cashed out in terms of her likelihood of speaking the truth. Second, if a certain speaker's testimony has sufficient epistemic weight to be believed by hearer1, then it should also be believed by hearer2. Third, the normative constraint here is evidentially grounded: whether or not a hearer should believe a speaker depends on the evidence the hearer has that the speaker is telling the truth. I argue that there are cases of testimonial knowledge transmission that are incompatible with these three claims. This is when one accepts the testimony of an intimate friend.

Testimonial knowledge sometimes depends on internalist epistemic conditions, those that thinkers are able to reflect upon. In the testimony literature the only internalist conditions that are considered are those concerning a hearer's knowledge of a speaker's reliability. I argue, however, that the relevant sense of internal"" should not be seen as referring to just the hearer's point of view, but rather to the points of view of both the hearer and the speaker. There are certain cases of testimonial knowledge transmission that depend on the speaker's knowledge of his audience. These include cases of ""engineered knowledge"" in which a speaker deviously manipulates a hearer's beliefs. Such knowledge is therefore internalist because it depends on factors that are internal to the point of view of the speaker, and not merely on externalist factors such as the reliability of the speakers' and hearers' beliefs."