by Scott F. Aikin and Robert B. Talisse
Disagreement is a pervasive feature of our ordinary lives. We disagree with family members over what would make for a good Tuesday night dinner, with colleagues over how to solve some thorny problem, and with neighbors over whether the new highway off-ramp is a good or bad thing for the neighborhood. News stories are often about disagreements, and their online comments sections are sites where the disagreements may continue to be aired.
In some cases of disagreement, we may know more about the issue than the other person. And in some cases, the other person may know more. Call these asymmetric disagreements, and a regular thought is that in these cases, the less knowledgeable person ought to defer to the more. However, it's possible for there to be symmetric disagreements, where both sides are roughly as knowledgeable of and capable with the evidence on the issue. The individuals in these instances, then, are peers, at least epistemically.
In these symmetric cases, how should these peers view their own and their disagreeing interlocutors' commitments? By hypothesis, the two opposing views are based on the same evidence, so it's not that one can view one side as better informed or less knowledgeable than the other. And it seems dogmatic, or at least unfounded, to say that one just knows (without more evidence) that one's view is better off than one's opposition.
A background question to this matter is whether it's possible for a set of evidence to justify more than one view about an issue. One take on the question is that, given a set of evidence, there is only one attitude a person may take about it – one may accept a proposition as justified, one may reject it and hold its denial as justified by the evidence, or one may be justified only in suspending judgment on the matter. Of these three options, only one of them would be rationally responsible. Call this view the Uniqueness Thesis – that there is only one attitude that any set of evidence justifies.