Date of Award

Spring 2020

Document Type


Degree Name

Doctor of Philosophy (PhD)



First Advisor

Wreen, Michael

Second Advisor

Adams, Noel

Third Advisor

Harrison, Stanley


The epistemological issue of disagreement comprises several related problems which arise in relation to disagreeing with another person. The central questions at issue are: (1) Can a body of evidence confer rationality on opposed propositions? (2) What is the relevance of unshareable evidence to disagreement? (3) What are one’s epistemic responsibilities in the context of disagreement? I consider several arguments from the recent disagreement literature which suggest that reasonable disagreements between people who have shared their evidence and are epistemic peers--i.e., they are equally informed about the disputed issue, and are roughly equal with respect to intelligence, thoughtfulness, carefulness, alertness, and so on--are not possible. I also consider several arguments which suggest that one may rationally persist in one’s views in spite of peer disagreement. In the course of considering these arguments, I discuss the role of “evidential seemings,” seemings of the form “It seems to one that evidence E supports proposition p”; their analogous relationship to perceptual seemings; and how such seemings might be outweighed by higher-order evidence provided by peer disagreement.I propose that the most difficult and interesting aspect of the peer disagreement problem is prolonged disagreement with a recognized epistemic peer, which may undermine one’s evidential seemings in the form of Parity: in the context of peer disagreement, both parties may be aware that things would seem just the same to them as they do if in fact the other party were correct and they were mistaken. This presents a localized skeptical problem that affects what one should believe in the context of such a disagreement, because prolonged peer disagreement puts one’s own evidential seemings into conflict. I propose and discuss three possible solutions to the Parity Problem, one inspired by David Hume, and two inspired by Immanuel Kant: (1) Practical considerations stemming from the underdetermination of one’s views by the available evidence as well as one’s larger epistemic goals can justify maintaining one’s view. Alternatively, judgments that someone else is an epistemic peer may be classified as either (2) empty regulative theoretical judgments (a Kantian category), or (3) non-theoretic judgments (analogous to judgments about taste). In either case, rational disagreement under Parity is possible.

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