Background for Disagreement

Disagreement is one of the three primary topics in Karl’s course on rationality that I’m taking this semester, and it’s the topic I’ll most likely be writing on.  While disagreement is currently a hot topic in epistemology, it hasn’t really been a perennial topic in philosophy in the way that it’s presently discussed.  So this post will lay out some of the terrain as background.

Intuitively, someone is your ‘epistemic peer’ when they are your equal in reasoning and possess the same body of evidence that you possess.  It will most often be natural to consider epistemic peerhood as being relative to a particular subject matter.  Perhaps I am your epistemic peer with respect to philosophy, your epistemic inferior with respect to music, and your epistemic superior with respect to lolcats.  The core topic of the literature is how to respond to disagreement with someone who is your epistemic peer (alternately, someone you consider to be your epistemic peer).  Some authors, especially Elga, try to develop an account that naturally extends to cover the case of someone who differs from you in access to evidence or in reasoning ability.  Another desideratum is that the account of disagreement meshes with reflection principles that govern how the credences of one’s past, present and future selves must relate.

There are at least three basic ways to construe the attitude of regarding someone as an epistemic peer:

  1. You view someone as an epistemic peer when you take them to have the relevant epistemic virtues to the same extent that you do.
  2. You view someone as an epistemic peer when you think that they are just as reliable with regard to the subject matter as you are.
  3. You view someone as an epistemic peer if, prior to discussing a topic, your credence that you would be right in case of a disagreement equals your credence that they will be right.  Note that the credence is conditioned on the mere fact of the disagreement, not the particular positions that you might take or the chains of reasoning you use.

How do 2 & 3 differ? Intuitively, you might believe that someone is as reliable as you because you think that they’ll give the same answers that you do.  But when you disagree, you gain evidence that undermines your previous grounds for thinking that they were reliable.

Two natural worries arise even before considering specific views, though be warned, I’m going to end up punting on each of question.  First, why should we care? Supposing we can answer the question of how to respond to disagreement with epistemic peers, why should we think that this is a philosophical advance? There’s a lot of possible answers here, and a lot depends on how various theories within the field fare.  One thought is simply that the regular existence of protracted disagreements among good faith investigators is itself a remarkable phenomenon, and that we should want to know how to respond to it.  More specifically, we find ourselves unable to persuade seemingly honest and conscientious opponents of our positions with regard to moral, philosophical or scientific questions.  Does the mere fact of disagreement force us to give up our confidence (if we ever had any…) that we are right about those questions?  That’s merely intuitive reason to think the problem is important–perhaps you have no inclination to think that disagreement is seriously a problem.

Second, why should we think of disagreement as a unitary phenomenon? Why not think the appropriate response to disagreement varies so greatly that no useful generalizations will be forthcoming? I have substantial sympathy for this thought–my current line of thought would deny that there are any surprising generalizations about how to handle disagreement.  One hunch is that if disagreement turns out to be a heterogous phenomenon, then the ways in which disagreement matters to different intellectual endeavors may turn out to shed some light on how the underlying endeavors differ.  And if that doesn’t work, I’m interested in the moral case, so I’ll take whatever insight I can get into it.  Of course, saying whether or not there are any interesting generalizations to be made about disagreement can’t be until you’ve actually investigated the subject.

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