5. Rational Disagreement

Here I consider at greater length the possibility of rational disagreement as a response to the problem.   Consider two or more epistemic peers holding contrary views on the same issue.  Can they each justifiedly believe either A or B?

My epistemic peers disagree with me on this issue.  I am right, but they are each wrong.  I am justified in holding my view, but they are not justified in holding theirs.

My epistemic peers disagree with me on this issue.  I am right, but they are each wrong.  I am justified in holding my view, and they are also justified in holding theirs.

If rational disagreement is possible, then sometimes it is justifiable for more than one member of a dispute to accept A, B, or something similar.

In current epistemology, there is disagreement about whether rational disagreement is possible.  E.g., Richard Feldman argues that reasonable disagreement between peers is not possible under common circumstances, because there is generally at most a uniquely justified belief in light of a given set of evidence.[^9]   Adam Elga holds that when one discovers that one disagrees with an epistemic peer, one should give the peers’ views equal weight as one’s own.[^10]   David Christenson argues that when on has disagreement with peers, this typically should occasion belief-revision towards the views of one’s peers and vice versa.[^11] In contrast, Thomas Kelly holds that one often need not revise one’s views in light of discovering disagreement with one’s peers because one believes they have misjudged the evidence.[^12]   Gideon Rosen holds that rationality is permissive and that sometimes one is permitted to choose among competing theories when given a set of evidence.[^13]

Nicholas Rescher explicitly addresses the problem of philosophical dissensus.  He argues that philosophers choose to reject different theses—and thus establish conflicting schools of thought—because they accept differentcognitive values or weigh the cognitive values differently. [^14]   Cognitive values are the epistemic traits by which we assess a doctrine, e.g., coherence, plausibility, generality, importance, informativeness, elegance, etc.  A philosopher who more strongly values plausibility and intuitiveness is likely to accept different doctrines from those a philosopher who more strongly values systematicity would accept.  Rescher argues that differences over the relative weights of cognitive values cannot fully be resolved. According to Rescher, rational theory acceptance means accepting a theory that does justice to one’s cognitive values.  Different theorists can reasonably accept different values to different degrees.  So, rational disagreement is possible.

It might be thought that the possibility of rational disagreement will bear on whether outsider scepticism is warranted in light of philosophical dissensus.  For instance, Peter van Inwagen discusses people who have heard philosophical debates but have remained agnostic. He then says,

I think that any philosophy who does not wish to be a philosophical sceptic…must agree with me that…it must be possible for one to be justified in accepting a philosophical thesis when there are philosophers who, byall objective and external criteria, are at least as equally well qualified to pronounce on that thesis and who reject it.[^15]

However, it is possible that whether the agnostic should become a sceptic and whether the non-agnostic philosopher should become an agnostic sceptic are distinct problems.  Perhaps rational disagreement is possible among peers, and this excuses non-agnostic philosophers from having to become agnostic sceptics.  However, as I will argue in this section, even if this is so, this does not give reason for the truth-seeking, error-avoiding agnostic to become a non-agnostic. Rather, she should be a sceptic about philosophy.

Note that if rational disagreement were impossible, this would serve my thesis, as it would bolster the case for outsider scepticism.  If rational disagreement is impossible, then insiders (non-agnostic philosophers) should become sceptics.  Presumably this means that outsiders (agnostics who have not studied philosophy) should become sceptics as well, once they learn that all the insiders are rationally obligated to become sceptics.  However, I will assume for the sake of argument that rational disagreement among epistemic peers is possible. I will argue that even if it is possible, this will not be enough to show the truth-seeking, error-avoiding agnostic that she ought to pursue philosophy and adopt any views.  The possibility of rational disagreement does not defeat outsider scepticism.

Since I am granting that rational disagreement is possible, I need not consider Rosen’s, Kelly’s, or others’ arguments for rational disagreement at length or with much precision.  I need only consider their conclusion: rational disagreement is possible.  If so, then it follows that when I recognize that my epistemic peers disagree with me on some issue, sometimes I may still justifiedly believe that my view is true.  (I take it that believing that X and believing that X is true are the same thing.)  In addition, depending on one’s view of rational disagreement, this might mean I am justified in believing I am justified, and perhaps even in believing that my peers are justified in having similar attitudes toward themselves.

So, what rational disagreement arguments deliver us, at the end, is something like B: ‘Even though my epistemic peers disagree with me on this issue, I am right, they are all wrong, I am justified in holding my view, and they are also justified in holding theirs.’  If I am justified in holding B, then insider scepticism is defeated.  I am not required to become an agnostic and a sceptic.

However, notice that B isnot what truth-seeking, error-avoiding agnostic wants.  She comes to philosophy hoping to obtain true answers to philosophical questions while avoiding error.  If rational disagreement is possible, then philosophical inquiry can get her justified belief in various philosophical doctrines even in the presence of disagreement, but that was not what she asked for.  A justified belief that one has the truth on some issue is a great thing to have - I certainly would like to have that - but it is a poor substitute for bona fide truth.  The truth-seeking, error-avoiding agnostic is not interested in this substitute.

She might be impressed to learn (depending on what the standards are for rational disagreement) that many or perhaps all philosophers are justified in their beliefs.  With some good fortune, we might discover thatall actual philosophical disagreements among members of the APA are reasonable ones, and so no philosopher must do any belief revision or become a sceptic.  However, this still does not give the truth-seeking, error-avoiding agnostic reason to become a believer.  She wants a greater than not chance of getting true beliefs about most philosophical issues.  Even a 100% chance of getting a justified belief that one has the truth about philosophical issues or (more simply) a 100% chance of getting justified beliefs about philosophical issues will not motivate her, because there are not the same things as a true beliefs about most philosophical issues. They are poor surrogates.

Rescher’s defence of philosophy is particularly clear in how it fails to satisfy this sort of agnostic.  (This is not to say his defence is bad, but just that it is not what I called a proper epistemic defence.) Rescher holds that it can instrumentally rational to accept a theory based on one’s cognitive values.  There is a plurality of reasonable stances on the weights of these cognitive values.  So, for Rescher, rational disagreement rests precisely on these cognitive values rather than on truth.  But our agnostic is not interested in these cognitive unless they reliably get her to the truth.  Apparently, they do not, because ex hypothesi the pursuit of theories by different people with different cognitive values or weights for these values results in dissensus.

The agnostic asks us if we can get her the truth.  In light of dissensus, apparently we have to say no.  All we can offer is justified belief.

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