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When two epistemic peers — agents with equal evidence and roughly equal reasoning ability — reach contradictory conclusions on the same question, what should each do? Conciliationists argue that disagreement is itself evidence that something has gone wrong, and each party should move toward the other's view (the 'equal weight view'). Steadfasters hold that if you have done your epistemic work carefully, you may rationally maintain your position even in the face of peer disagreement, since the disagreement itself does not add new first-order evidence about the question. The debate has practical stakes in political disagreement, scientific consensus, and religious diversity.
Work through the 'restaurant bill' case (Christensen): two careful people calculate and reach different totals. Then scale up to philosophical and scientific disagreement, asking whether the same conciliatory response applies. Notice that conciliationism appears self-undermining: if peers disagree about conciliationism, should they conciliate about that too?
Your prerequisite work on testimony introduced you to the idea that other people's assertions are a genuine source of evidence — and that evaluating testimony requires calibrating how much epistemic weight to give different speakers. The epistemology of disagreement extends this into a sharper puzzle: what should happen when two equally qualified thinkers, with access to the same evidence, reach opposite conclusions? This is not the ordinary case of getting new information from a better-informed source. It is the case where you have done your best reasoning and someone equally capable has done theirs and ended up somewhere else entirely.
The concept of an epistemic peer is the key technical term. Two agents are epistemic peers on some question if they have examined the same body of evidence and have roughly equal reasoning ability and reliability. In practice this ideal is never perfectly met — people always bring different background assumptions, slightly different interpretations of shared evidence, and different cognitive styles. But the idealized case isolates the theoretical question cleanly: when you discover that a genuine peer disagrees, does that discovery itself constitute evidence that you are wrong?
Conciliationism says yes. On the equal weight view, you should treat your peer's conclusion as evidence on a par with your own, and average the two positions — moving toward the middle. The argument is that, before the disagreement, you had some probability of being right; your peer also had roughly that probability of being right; discovering that they reached a different conclusion is evidence that something went wrong in one of your reasoning chains, and you cannot know whose. So rational updating requires reducing your confidence and moving toward theirs. The restaurant bill example (from David Christensen) makes this vivid: you and a trusted friend both calculate the bill carefully and arrive at different totals. You should not simply assert your total; you should look again, take their figure seriously, and hold your answer more tentatively than before.
Steadfastness pushes back. The steadfast position holds that your first-order reasoning — the actual work you did evaluating evidence — is the primary guide to what you should believe. Discovering that a peer disagrees gives you *higher-order* information (information about the process rather than the object of inquiry), but it is not the same as new first-order evidence about the question itself. If I have carefully evaluated the evidence for climate policy and reached a well-supported conclusion, learning that an economist reached a different conclusion might prompt me to recheck my reasoning, but it does not automatically require me to shift my view. The peer's disagreement tells me someone disagreed — not that they are right and I am wrong.
The deepest problem for conciliationism is that it appears self-undermining. If conciliationism is correct, then when two epistemic peers disagree about whether conciliationism is true — one accepting it and one rejecting it — both should conciliate and move toward each other's view. But that conciliation would produce something like "mild conciliationism," which is itself a contested position, prompting further conciliation, and so on. The view seems to eat itself when applied reflexively. This has led to proposals for partial or restricted versions of conciliationism — rules that apply in some domains (math, empirical science) but not others (where values or interpretive frameworks fundamentally diverge). The practical stakes are real: how should a scientist respond to climate denial, a judge to precedents she thinks were wrongly decided, or a voter to confident disagreement from someone equally informed?
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