Matt Weiner

I argue that there is a wide variety of epistemic norms, distributed along two different spectra. One spectrum runs from the ideal to the practical and concerns the extent to which it is possible to follow the norm given our cognitive and epistemic limitations. The other spectrum runs from thin to thick and concerns the extent to which the norm concerns facts about our beliefs over and above the content of the belief. Many putative epistemic norms, such as truth and various conceptions of justification, can be found at different points on the spectra. There is no single obvious privileged point from which to say any of these norms is more fundamental than the others, though there may be some reason to doubt that some of the norms are intrinsically interesting.

I propose that testimony is subject to a norm that is backed by a credibility sanction: whenever the norm is violated, it is appropriate for the testifier to lose some credibility for their future testimony. This is one of a family of sanction-based norms, where violation of the norm makes it appropriate to lose some power; in this case, the power to induce belief through testimony. The applicability of the credibility norm to testimony follows from the epistemology of testimony, in that false or unjustified testimony weakens the reason for belief that is provided by the speaker's future testimony.

Testimony is an indispensable way of gaining knowledge and also a voluntary act for which the teller can be held responsible. This dissertation analyzes these two aspects of testimony, the epistemological and the normative. Indeed, it argues that these two aspects cannot be separated: A satisfactory account of testimony's epistemology must allow for testimony's normative status, while an account of testimony's normative status can be derived from testimony's epistemology. ;Epistemologically, the general reliability of testimony should be treated differently from the reliability of particular pieces of testimony. We are justified in believing that testimony is generally reliable, without needing evidence to that effect. This avoids the problems that would arise from attempting to gather evidence for testimony's general reliability. Particular pieces of testimony, however, can only provide a justification for belief by providing evidence for what is told. This view about particular pieces of testimony faces the problem of how the teller can present her testimony as evidence while accepting responsibility for it, and how the hearer can take testimony as evidence while holding the hearer responsible for it. ;To solve this problem, I give an account, based on inference to the best explanation, of the specific way testimony provides evidence for what is told. To see testimony as evidence for what is told, we must explain it in terms of the reasons people have for choosing to say one thing rather than another. On this account, the evidence that testimony provides depends on the teller's choice to assume responsibility for her testimony, rather than precluding that assumption of responsibility. ;On the other hand, the epistemology of testimony imposes certain norms on the act of telling someone something. The teller is responsible for the truth of her testimony, in that she stakes her future credibility on its truth. Loss of credibility would count as a sanction for violating the responsibility to tell the truth, because a teller ordinarily intends her testimony to be believed. This responsibility to tell the truth is derived from the epistemology of testimony

I defend the acceptance principle for testimony (APT), that hearers are justified in accepting testimony unless they have positive evidence against its reliability, against Elizabeth Fricker's local reductionist view. Local reductionism, the doctrine that hearers need evidence that a particular piece of testimony is reliable if they are to be justified in believing it, must on pain of scepticism be complemented by a principle that grants default justification to some testimony; I argue that (APT) is the principle required. I consider two alternative weaker principles as complements to local reductionism; one yields counter-intuitive results unless we accept (APT) as well, while the other is too weak to enable local reductionism to avoid scepticism

We suggest a rigorous theory of how objective single-case transition probabilities fit into our world. The theory combines indeterminism and relativity in the “branching space–times” pattern, and relies on the existing theory of causae causantes (originating causes). Its fundamental suggestion is that (at least in simple cases) the probabilities of all transitions can be computed from the basic probabilities attributed individually to their originating causes. The theory explains when and how one can reasonably infer from the probabilities of one “chance set-up” to the probabilities of another such set-up that is located far away.

Suppose we consider knowledge to be valuable because of the role known propositions play in practical reasoning. This, I argue, does not provide a reason to think that knowledge is valuable in itself. Rather, it provides a reason to think that true belief is valuable from one standpoint, and that justified belief is valuable from another standpoint, and similarly for other epistemic concepts. The value of the concept of knowledge is that it provides an economical way of talking about many epistemic concepts that are valuable in itself from one standpoint or another. In this way knowledge is like a Swiss Army Knife; a Swiss Army Knife is not useful as such on any occasion, but it provides an efficient way of carrying around different tools that are useful in themselves on different occasions.

This essay critically examines the Assurance View of testimony as put forth by Angus Ross (1986) and Richard Moran (1999). The Assurance View holds that someone who offers testimony gives the hearer a non-evidential justification for belief by assuming responsibility for the truth of her testimony. I agree that testimonial justification depends on the teller’s assumption of her responsibility for her testimony, but argue that it is nevertheless evidential justification. Testimonial justification is a sort of evidence that is within the teller’s power to create or withhold at will, and that power is essential to the justification.

The knowledge account of assertion holds that it is improper to assert that p unless the speaker knows that p. This paper argues against the knowledge account of assertion; there is no general norm that the speaker must know what she asserts. I argue that there are cases in which it can be entirely proper to assert something that you do not know. In addition, it is possible to explain the cases that motivate the knowledge account by postulating a general norm that assertions would be true, combined with conversational norms that govern all speech acts. A theory on which proper assertions must be true explains the data better than a theory on which proper assertions must be known to be true.

It has been claimed that justification, conceived traditionally in an internalist fashion, is not an epistemologically important property. I argue for the importance of a conception of justification that is completely dependent on the subject’s experience, using an analogy to advice. The epistemological importance of a property depends on two desiderata: the extent to which it guarantees the epistemic goal of attaining truth and avoiding falsehood, and the extent to which it depends only on the information available to the believer. The traditional intermalist notion of justification completely satisfies the second desideratum and largely satisfies the first.