Group disagreement: a belief aggregation perspective

The debate on the epistemology of disagreement has so far focused almost exclusively on cases of disagreement between individual persons. Yet, many social epistemologists agree that at least certain kinds of groups are equally capable of having beliefs that are open to epistemic evaluation. If so, we should expect a comprehensive epistemology of disagreement to accommodate cases of disagreement between group agents, such as juries, governments, companies, and the like. However, this raises a number of fundamental questions concerning what it means for groups to be epistemic peers and to disagree with each other. In this paper, we explore what group peer disagreement amounts to given that we think of group belief in terms of List and Pettit’s (Econ Philos 18:89–110, 2002; Group agency: the possibility, design, and status of corporate agents, Oxford University Press, Oxford, 2011) ‘belief aggregation model’. We then discuss how the so-called ‘equal weight view’ of peer disagreement is best accommodated within this framework. The account that seems most promising to us says, roughly, that the parties to a group peer disagreement should adopt the belief that results from applying the most suitable belief aggregation function for the combined group on all members of the combined group. To motivate this view, we test it against various intuitive cases, derive some of its notable implications, and discuss how it relates to the equal weight view of individual peer disagreement.

     

Disagreement and Evidential Attenuation

What sort of doxastic response is rational to learning that one disagrees with an epistemic peer who has evaluated the same evidence? I argue that even weak general recommendations run the risk of being incompatible with a pair of real epistemic phenomena, what I call evidential attenuation and evidential amplification. I focus on a popular and intuitive view of disagreement, the equal weight view. I take it to state that in cases of peer disagreement, a subject ought to end up equally confident that her own opinion is correct as that the opinion of her peer is. I say why we should regard the equal weight view as a synchronic constraint on (prior) credence functions. I then spell out a trilemma for the view: it violates what are intuitively correct updates (also leading to violations of conditionalisation), it poses implausible restrictions on prior credence functions, or it is non‐substantive. The sorts of reasons why the equal weight view fails apply to other views as well: there is no blanket answer to the question of how a subject should adjust her opinions in cases of peer disagreement.     

Peer Disagreement and Two Principles of Rational Belief

This paper presents a new solution to the problem of peer disagreement that distinguishes two principles of rational belief, here called probability and autonomy. When we discover that we disagree with peers, there is one sense in which we rationally ought to suspend belief, and another in which we rationally ought to retain our original belief. In the first sense, we aim to believe what is most probably true according to our total evidence, including testimony from peers and authorities. In the second, we aim to base our beliefs only on objective evidence and argumentation, even if that lowers the probability of their being true. The first principle of rational belief tends to serve the short-term epistemic interests of individuals, while the second tends to serve the long-term epistemic interests of both individuals and groups. The best way to reconcile these principles in cases of peer disagreement is to associate them with two corresponding species of belief, here called perception and opinion.     

Is it Safe to Disagree?

This paper offers a new account of the epistemic significance of disagreement which is grounded in two assumptions; (i) that knowledge is the norm of belief and, (ii) that the safety condition is a necessary condition for knowledge. These assumptions motivate a modal definition of epistemic peerhood, which is much easier to operate on than the more traditional definitions of epistemic peerhood. The modal account of the epistemic significance of disagreement yields plausible results regarding cases of disagreement. Furthermore, it is able to tap into the intuitions that have motivated the conformist and the nonconformist positions and it locates a fruitful middle‐ground between these two conflicting positions. It will be shown that the conformist is correct in that cases of real peer disagreement force us to suspend our judgment. The reason for this is that in cases of real peer disagreement our beliefs fail to be safe. The nonconformist, on the other hand, is right in that disagreement in itself does not have any epistemic power. It is only by the grace of nature that we gain knowledge. The fact that someone disagrees with you does not mean that you do not have knowledge.     

On Merely Modal Epistemic Peers: Challenging the Equal-Weight View

There is a controversy, within social epistemology, over how to handle disagreement among epistemic peers. Call this the problem of peer disagreement. There is a solution, i.e. the equal-weight view, which says that disagreement among epistemic peers is a reason for each peer to lower the credence they place in their respective positions. However, this solution is susceptible to a serious challenge. Call it the merely modal peers challenge. Throughout parts of modal space, which resemble the actual world almost completely, there are hordes of epistemic peers, who disagree with almost any arbitrarily chosen belief had by residents of the actual world. Further, the mere modality of these peers is not itself an epistemic difference-maker. Thus, on the equal-weight view, we should significantly lower the credence we place in most of our beliefs. Surely, this is seriously mistaken. Thus, there are serious considerations that cut against the equal-weight view.     

Multi‐Peer Disagreement and the Preface Paradox

The problem of multi‐peer disagreement concerns the reasonable response to a situation in which you believe P₁ … P_n and disagree with a group of ‘epistemic peers’ of yours, who believe ～P₁ … ～P_n, respectively. However, the problem of multi‐peer disagreement is a variant on the preface paradox; because of this the problem poses no challenge to the so‐called ‘steadfast view’ in the epistemology of disagreement, on which it is sometimes reasonable to believe P in the face of peer disagreement about P. After some terminology is defined (§1), Peter van Inwagen's challenge to the steadfast view will be presented (§2). The preface paradox will then be presented and diagnosed (§3), and it will be argued that van Inwagen's challenge relies on the same principle that generates the preface paradox (§4). The reasonable response to multi‐peer disagreement will be discussed (§5), and an objection addressed (§6).     

A diachronic perspective on peer disagreement in veritistic social epistemology

The main issue in the epistemology of peer disagreement is whether known disagreement among those who are in symmetrical epistemic positions undermines the rationality of their maintaining their respective views. Douven and Kelp have argued convincingly that this problem is best understood as being about how to respond to peer disagreement repeatedly over time, and that this diachronic issue can be best approached through computer simulation. However, Douven and Kelp’s favored simulation framework cannot naturally handle Christensen’s famous Mental Math example. As a remedy, I introduce an alternative (Bayesian) simulation framework, Laputa, inspired by Alvin Goldman’s seminal work on veritistic social epistemology. I show that Christensen’s conciliatory response, reasonably reconstructed and supplemented, gives rise to an increase in epistemic (veritistic) value only if the peers continue to recheck their mental math; else the peers might as well be steadfast. On a meta-level, the study illustrates the power of Goldman’s approach when combined with simulation techniques for handling the computational issues involved.

     

How to respond rationally to peer disagreement: The preemption view

In this paper, I argue that the two most common views of how to respond rationally to peer disagreement—the Total Evidence View (TEV) and the Equal Weight View (EWV)—are both inadequate for substantial reasons. TEV does not issue the correct intuitive verdicts about a number of hypothetical cases of peer disagreement. The same is true for EWV. In addition, EWV does not give any explanation of what is rationally required of agents on the basis of sufficiently general epistemic principles. I will then argue that there is a genuine alternative to both views—the Preemption View (PV)—that fares substantially better in both respects. I will give an outline and a detailed defense of PV in the paper.     

Distant Peers

What is the nature of rational disagreement? A number of philosophers have recently addressed this question by examining how we should respond to epistemic conflict with a so‐called epistemic peer—that is, someone over whom you enjoy no epistemic advantage. Some say that you're rationally required to suspend judgment in these cases—thereby denying the very possibility of a certain kind of rational disagreement. Others say that it's permissible to retain your beliefs even in the face of epistemic conflict. By distinguishing between close peers and distant peers, I argue that it's rational to respond to different types of peers in different ways. I also argue that remote peers—a particularly distant kind of distant peer—provide us with an important lesson in epistemic humility.     

Disagreement,the Independence Thesis,and the Value of Repeated Reasoning

The problem of peer disagreement is to explain how you should respond when you and a peer have the same evidence bearing on some proposition $P$ and are equally competent epistemic agents, yet have reached opposite conclusions about $P$. According to Christensen's Independence Thesis, in assessing the effect of your peer's disagreement, you must not rely on the reasoning behind your initial belief. I note that ‘the reasoning behind your initial belief’ can be given either a token or type reading. I argue that the type reading is false, but the token reading is extremely weak.     

Undermining, circularity, and disagreement

Sometimes we get what seem to be good reasons for believing that we’ve misevaluated our evidence for a proposition P. In those cases, can we use our evidence for P itself to show that we haven’t misevaluated our evidence for P? I show why doing so appears to employ viciously circular reasoning. However, I then argue that this appearance is illusory in certain cases and that we sometimes can legitimately reason in that way. This claim sheds new light on the nature of epistemic undermining and epistemic circularity. In addition, it has implications for the current debate about the epistemic significance of disagreement. An important and influential position in that debate says that disagreement with others dramatically undermines our justification for a wide range of our opinions (e.g., political, religious, moral, economic, and philosophical opinions). My view on undermining and circularity implies that this position on disagreement rests on a mistake.     

Reflection and Disagreement

How should you take into account the opinions of an advisor? When you completely defer to the advisor's judgment (the manner in which she responds to her evidence), then you should treat the advisor as a guru. Roughly, that means you should believe what you expect she would believe, if supplied with your extra evidence. When the advisor is your own future self, the resulting principle amounts to a version of the Reflection Principle—a version amended to handle cases of information loss. When you count an advisor as an epistemic peer, you should give her conclusions the same weight as your own. Denying that view—call it the “equal weight view”—leads to absurdity: the absurdity that you could reasonably come to believe yourself to be an epistemic superior to an advisor simply by noting cases of disagreement with her, and taking it that she made most of the mistakes. Accepting the view seems to lead to another absurdity: that one should suspend judgment about everything that one's smart and well‐informed friends disagree on, which means suspending judgment about almost everything interesting. But despite appearances, the equal weight view does not have this absurd consequence. Furthermore, the view can be generalized to handle cases involving not just epistemic peers, but also epistemic superiors and inferiors.     

A puzzle about belief updating

In recent decades much literature has been produced on disagreement; the puzzling conclusion being that epistemic disagreement is, for the most part, either impossible (e.g. Aumann (Ann Stat 4(6):1236–1239, 1976)), or at least easily resolvable (e.g. Elga (Noûs 41(3):478–502, 2007)). In this paper I show that, under certain conditions, an equally puzzling result arises: that is, disagreement cannot be rationally resolved by belief updating. I suggest a solution to the puzzle which makes use of some of the principles of Hintikka’s Socratic epistemology.     

From Independence to Conciliationism: An Obituary

Conciliationists about peer disagreement hold that when one disagrees with an epistemic peer about some proposition p, one should significantly change one's view about p. Many arguments for conciliationism appeal to a principle Christensen [2011] dubs Independence. Independence says that evaluations of the beliefs of those with whom one disagrees should not be made on the basis of one's initial reasoning about p. In this paper, I show that this principle is false. I also show that two weaker principles that vindicate conciliationism are either false, unmotivated, or both.     

Possible disagreements and defeat

Conciliatory views about disagreement with one’s epistemic peers lead to a somewhat troubling skeptical conclusion: that often, when we know others disagree, we ought to be (perhaps much) less sure of our beliefs than we typically are. One might attempt to extend this skeptical conclusion by arguing that disagreement with merely possible epistemic agents should be epistemically significant to the same degree as disagreement with actual agents, and that, since for any belief we have, it is possible that someone should disagree in the appropriate way, we ought to be much less sure of all of our beliefs than we typically are. In this paper, I identify what I take to be the main motivation for thinking that actual disagreement is epistemically significant and argue that it does not also motivate the epistemic significance of merely possible disagreement.     

Group Peer Disagreement

A popular view in mainstream social epistemology maintains that, in the face of a revealed peer disagreement over p, neither party should remain just as confident vis‐a‐vis p as she initially was. This ‘conciliatory’ insight has been defended with regard to individual epistemic peers. However, to the extent that (non‐summativist) groups are candidates for group knowledge and beliefs, we should expect groups (no less than individuals) to be in the market for disagreements. The aim here will be to carve out and explore an extension of the conciliatory insight from individual peer disagreement to group peer disagreement; in doing so, I'll raise and address three key problems that face any plausible defence of such a constraint.     

The Contextual Character of Causal Evidence

I argue for the thesis that causal evidence is context-dependent. The same causal claim may be warranted by the same piece of evidence in one context but not another. I show this in particular for the type of causal evidence characteristic of the manipulability theory defended by Woodward (Making things happen: a theory of causal explanation. Oxford University Press, Oxford, 2003). My thesis, however, generalises to other theories—and at the end of the paper I outline the generalization to counterfactual theories. The paradigmatic form of causal evidence in the manipulability theory is provided by tests of the functional invariance of the relation between putative cause and effect under interventions (on the putative cause). I show that such evidence exhibits at least two kinds of context-relativity: personal, or epistemic; and situational, or objective.     

How Common is Peer Disagreement? On Self‐Trust and Rational Symmetry

In this paper I offer an argument for a view about the epistemology of peer disagreement, which I call the “Rational Symmetry View”. I argue that this view follows from a natural (if controversial) conception of the epistemology of testimony, together with a basic entitlement to trust our own faculties for belief formation. I then discuss some objections to this view, focusing on its relationship to other well‐known views in the literature. The upshot of this discussion is that, if the Rational Symmetry View is correct, much of the action in the epistemology of disagreement relates—not to how one should treat those one regards as an “epistemic peer” in the sense popular in that literature—but rather to who one should treat as such.     

Medical knowledge in a social world: Introduction to the special issue

Philosophy of medicine has traditionally examined two issues: the scientific ontology for medicine and the epistemic significance of the types of evidence used in medical research. In answering each question, philosophers have typically brought to bear tools from traditional analytic philosophy. In contrast, this volume explores medical knowledge from the perspective offered by social epistemology. While many of the same issues are addressed, the approach to these issues generates both fresh questions and new insights into old debates. In addition, the broader purview offered by social epistemology opens up opportunities to address new topics such as the role of consensus conferences, epistemic injustice, the value of medical knowledge, continuing medical education, and industry funding. This article situates and summarizes the contributions to this special issue.