Group Knowledge and Epistemic Defeat

Abstract

If individual knowledge and justification can be vanquished by epistemic defeaters, then the same should go for group knowledge. Lackey (2014) has recently argued that one especially strong conception of group knowledge defended by Bird (2010) is incapable of explaining how it is that (group) knowledge is ever subject to ordinary mechanisms of epistemic defeat. Lackey takes it that her objections do not also apply to a more moderate articulation of group knowledge—one that is embraced widely in collective epistemology—and which she does not challenge. This paper argues that given certain background premises that are embraced by orthodox thinking in collective epistemology, the more moderate account of group knowledge cannot make sense of either psychological or normative epistemic defeaters. I conclude by offering some suggestions for how the more moderate proposal might avoid this result.

1. Introduction

Few philosophers are doing more these days to bridge the gap between mainstream (individualist) epistemology and collective epistemology than Jennifer Lackey,[1] and one of the most interesting applications of mainstream epistemology she has made to the epistemology of groups concerns the topic of epistemic defeat.

Epistemic defeaters for an individual’s (would-be) knowledge and epistemic justification are reasonably well understood.[2] The very simple picture is this: S’s knowledge or justification that p can be defeated either psychologically or normatively, in virtue of S in the former case possessing some belief, q or, in the latter, being such that S (epistemically) should believe q, where q is a proposition the truth of which would either (i) count against the truth of S’s belief that p—this is called a rebutting defeater—or (ii) indicate that S’s belief that p was unreliably formed or sustained—this is called an undercutting defeater. So there can be rebutting or undercutting psychological and normative defeaters. Defeaters themselves, can be defeated by other defeaters. However, when they are not, (undefeated) defeaters vanquish knowledge and justification.

Here’s a compelling and simple thought: if individual knowledge and justification can be vanquished by defeaters, then so too can group knowledge. In fact, it would be very odd indeed if group knowledge and justification were somehow undefeatable. (Two minds are not that much better than one!) The upshot of this point is that it is an ex ante constraint on any plausible account of group knowledge that it be in principle defeated through ordinary mechanisms of defeat; and if staying true to this constraint should come at the cost of implausible consequences, then all the worse for that theory of group knowledge.

With this kind of constraint in hand, Lackey (2014) has sought to show that Alexander Bird’s somewhat radical account of group knowledge is not viable.[3] I think Lackey is right, but that her argument does not go far enough. What she overlooks is that there is a way to argue reasonably straightforwardly to the conclusion that the more orthodox account of group knowledge (to which she doesn’t level this criticism) has no viable way to make sense of epistemic defeat either, and (unless the problem can be resolved) this stands to be a very serious problem for orthodoxy in collective epistemology.

Here is the plan. In Section 2 I distinguish between the radical account of group knowledge that Lackey targets, and the more moderate view she doesn’t. In Section 3, I outline just how it is Lackey thinks the radical view is hopeless in making sense of epistemic defeat. In Section 4 I argue that, at least on one very standard way of thinking about group belief (i.e., the joint commitment model), the more moderate view is just as hopeless in making sense of epistemic defeat as the more radical view. Section 5 then sketches some refinements to the joint commitment approach to group belief and shows how these refinements reveal some potential ways to save the more moderate account of group knowledge from the kinds of defeat-based objections raised in Section 3.

2. Two Kinds of Socially Extended Knowledge

Let’s now get clearer about the kind of group knowledge that will be at issue in what follows. Mainstream epistemology has traditionally concerned itself with the epistemic properties of the cognitive outputs of individuals (e.g., individual beliefs[4]). But we also attribute epistemic states such as belief and knowledge to groups; we ask what the FBI knew before 9/11 or what CERN knows about the Higgs-Boson and whether the jury was justified in its conclusion.[5]

Group knowledge is uncontroversial, per se, by the lights of mainstream epistemology, provided it is understood summatively. On a summativist conception of group knowledge, a group, A, knows that p iff most individuals in A know that p. Group knowledge, in this deflated sense, is just an aggregate of individual knowledge. A much more philosophically interesting conception of group knowledge is non-summativist. For the present purposes, it will be helpful to distinguish two very different non-summativist views, as Lackey (2014) herself does, along the lines of what each thesis epistemically tolerates of the members of group that collectively knows. First consider the version of the thesis that is widely endorsed in collective epistemology—call this Socially Extended Knowledge-Moderate (SEK-M):[6]

A classic example, one which Lackey notes, that used to motivate (non-summativist) group knowledge is given by Hutchins (1995) in his famous case of a ship crew skillfully navigating an Iwo Jima class amphibious assault ship to port.

As Lackey summarizes:

Whereas (SEK-M) tolerates an absence of individual knowledge, it nonetheless allows for epistemic requirements weaker than knowledge of its members, viz., that individual members jointly accept that p or jointly commit to the proposition that p.[8] There is, however, a more radical statement of group knowledge that Alexander Bird (2010) calls social knowing, which relaxes such a requirement entirely.

As Bird (2010) sees it, all a social structure must do to be a candidate social knower is to have (in short) characteristic propositional outputs, and characteristic mechanisms that ensure the reliability of the propositional outputs, which are themselves the inputs for social actions or for social-cognitive structures, including the same structure that produces the output.[10] Nowhere in this picture is a further requirement that any individual have any particular beliefs or knowledge.[11] To get a feel for why Bird opts for such liberal position here,[12] we need only consider his case of Dr. N., which will be important to Lackey’s critique.

Bird’s line on the case, in short, is that the scientific community knew the results of Dr. N’s paper all along, despite there being a period of time where everyone who knew about—or indeed, was aware of—the result, was dead. Bird’s diagnosis[13] of the Case of Dr. N. clearly shows he takes the radical (SEK-R) to be true.

3. Lackey on (SEK-R) and Epistemic Defeat

Once Dr. N. and everyone else who read the paper dies, a lot can happen, some of it bad. Lackey exploits this fact with some complexity; consider her case Addition, which she takes to pose defeater-based problems that—as she argues—can’t be overcome by (SEK-R), no matter what a proponent of (SEK-R) tries to do about it. Let d be a proposition representing the discovery Dr. N. is claimed to have made, and which was subsequently forgotten.[14] Now, here’s Lackey’s twist on the case:

Lackey takes it as obvious that, in Addition, the members of the scientific community believe that not-d; this is, she says, a “classic instance of a rebutting psychological defeater ” (2014: 293)—which defeats the would-be knowledge and justification in virtue of being believed, and counting against the truth of the target proposition—d.[16] With this observation in hand, she poses a dilemma to any would-be proponent of (SEK-R).

Obviously, given that Addition has all the signs of a case of rebutting psychological defeat, the first-horn of this dilemma looks prima facie best, but as Lackey argues, any would-be proponent of (SEK-R) who takes this horn in Addition will face two objections: a sceptical objection and an arbitrariness objection. The sceptical objection is, in short, that (SEK-R) can maintain the prima facie plausible result that the scientific community’s belief that not-d is a psychological defeater for the alleged knowledge that d only by allowing that social knowledge can be too easily defeated, given the prevalence of dissenting opinion amongst scientists.[17] However, even if this sceptical problem could be dealt with, another problem faces the proponent of (SEK-R) who takes the first horn: given that (SEK-R) implies that group knowledge needn’t (as in the case of Addition) supervene on individuals’ mental states, it would be epistemically arbitrary for mental states of individual members to contribute negatively but not positively to the group’s mental state.[18]

The second horn, however, looks no more promising. This involves the proponent of (SEK-R) denying that knowledge is defeated in Addition. This route looks unpromising from the start, as anyone who takes it needs to explain why defeat merely appears to be present in Addition. Even if this can be done, it’s unlikely it can be done without incurring further problems. Lackey here considers two routes: either deny that defeat is present at T₂ by submitting that a group can know that p even though the group believes that not-p; or deny that belief is a necessary condition on knowledge. As Lackey sees it, the first move here is in effect “exempting groups from the norms governing rationality and thus removing them from the realm of the rational altogether,” (2014: 17) whereas the second preserves rationality only by failing to save any distinction between a group knowing and being in a position to know.

All in all, this is a pretty powerful argument Lackey has leveled against (SEK-R). Of particular interest in what follows is that where (SEK-R) is obviously lacking, (SEK-M) looks as though it would have no obvious problem handling epistemic defeat, given that a proponent of (SEK-M) looks poised to sidestep altogether the kind of defeater-objection raised by Addition-style cases. After all, one who endorses (SEK-M) has space to claim that once there was no one around to believe the target proposition d, no knowledge of d was present.[19] Accordingly, Lackey does not try to foist a dilemma on the proponent of (SEK-M) as she did with (SEK-R), as the dilemma is premised upon the acceptance of the presence of group knowledge that d. Thus Lackey does not take the defeat-based issues she’s raised to make trouble for the more moderate position.

4. A New Argument from Defeat against (SEK-M)

I want to now suggest that it’s not obvious at all just how the more modest (SEK-M) is going to be able to make sense of epistemic defeat any better than the more radical proposal. First, I’ll advance an argument that (SEK), given certain background assumptions, can’t make sense of psychological defeat. I’ll then advance a similar argument with respect to normative defeat.

5. A New Manoeuvre

I conclude in this section by first sketching some key features of a model of group belief and knowledge I’ve defended elsewhere,[43] and then showing how this model (in virtue of these features) offers some prima facie promise for a proponent of (SEK-M) who seeks reconciliation with ordinary thinking about defeaters.

The shape that the model I propose takes is best presented as a kind of response to an oversimplification betrayed by one very natural strand of rejectionist thinking. For a clear sense of this strand, consider Preyer (2003: 9): ”Beliefs are gradual (quantitative) and have subjective probabilities, acceptance is a matter of quality . . . They have a feature of all or nothing." Reiterating this latter observation, rejectionist Meijers (1999: 81) puts the point tersely: ”We agree, or we do not.”[44]

A simple line of argument falls out of these rejectionist insights: we should reject that groups have beliefs, because whatever groups accept, qua agreements, they accept in an all-or-nothing fashion, where as beliefs don’t have such an all-or-nothing feature; rather, they are gradient.[45]

Though there is a clear sense in which agreement is (as Meijers suggests) an on-or-off affair, what is easily overlooked—by rejectionists and (JAB) proponents alike—is that there is significant flexibility with respect to the object of agreement, when that object is a representational attitude. And this is because there are very different ways we can rely on p, ways that themselves correspond with different levels of practical risk.

To unpack this point, consider a rather mundane observation in individualist epistemology concerning the relationship between credence, or degree of belief, and rational action. Contrast two cases where Stan believes his wallet is in his pocket. In the first case he is certain that his wallet is in his coat pocket (call this p), and in the second case, he is about .7 confident his wallet is in his coat pocket.[46]

Stan’s epistemic position in the first case rationalizes Stan’s acting as if p under a wider range of practical circumstances than does the second, where his epistemic position is not taken (by Stan) to be as good. Put differently, Stan’s being certain that p rationalizes acting as if p across situations of higher practical risk than will be rational for Stan to continue to act as if p when Stan’s epistemic position is regarded as lower, as in the second case. Accordingly, if it’s very important to be able to make a payment, Stan might well be rational in acting as if p if his situation is as it is in the first case, even if not in the second (even though Stan counts nonetheless as believing his wallet is in his pocket in the second case).[47]

This insight has interesting and fruitful applications in the arena of group belief.[48] Here is the central statement of the view I’ve defended elsewhere: A group can believe p in virtue of jointly accepting that p, where this involves an agreement to act as if p in the following qualified way: to act as if p across a range of practical circumstances that positively correlates with the group’s epistemic position, which is a position the individuals of the group (in jointly accepting that p) are obligated, qua members of the group, to update in systematized ways.

Call this the risk-responsiveness account of group belief. This is not the place to provide a full defense of the view,[49] though I want to conclude by gesturing toward some novel resources this proposal has for the purposes of making sense of epistemic defeat, where the previously considered approaches seemed lacking.

In particular, I’ll conclude by sketching how the risk-responsiveness approach to group belief stands, at least potentially, when paired with (SEK-M), to make sense of group psychological defeaters. The discussion here should make it clear how similar moves can be made to make sense of normative defeat, though I won’t argue for this here.

We can envision a move on the table that proceeds as follows: group psychological defeaters function by virtue of being had, and counting (in some way) against the group’s continuing to hold belief in the way it is held, and regardless of the truth-value or epistemic status of the defeater. On this picture, individual updates can (on the risk-responsiveness model) count against holding belief in the way it is held, and so can defeat group knowledge in this sense, and regardless of epistemic status or veracity of these updates.

This point can be illustrated by an example:

I think a case can be made, with reference to the risk-responsive model of group belief, that Variation-1 is structurally very closely akin to a rebutting psychological defeater, and likewise Variation-2 an undercutting psychological defeater, for the group belief that the three scholarships merit award to A, B, and C (in that order). And, furthermore, that this result is achieved in a way that avoids the kinds of objections canvassed in the previous sections to more traditional proposals embracing (SEK-M).

Consider that, in Variation-1 the updated information, which Rebus (qua member of the group) made available to the group (via the central database), played two roles, to update that the group’s epistemic position vis-a-vis the proposition that the three scholarships merit award to A, B, and C (in that order) is not as good as previously thought (previously, .7), and secondly, that the practical risk in play is in fact greater than previously anticipated. These updates, combined, very plausibly count against the group’s continuing to rely on the group belief that the scholarships merit award in the order previously accepted, across the range of practical circumstances that they would have previously relied on it. A proponent of (SEK-M) who insisted that, previously, group knowledge was present in the case now has a story to tell for how that knowledge is defeated. To the extent that—as is a popular position—knowledge is actionable[50] (given present levels of practical risk), the group’s information state (following Rebus’s updates) is not knowledge.

One important benefit of this story is that by replacing (JAB) with the risk-responsiveness account of belief, a certain problematic consequence can be avoided without rejecting (GMAP). To appreciate this point, suppose one were to attempt to redeploy the argument from Section 4.1 against the risk-responsiveness account. Here’s how the redeployed argument would go:[51]

If we were working with (JAB) rather than the risk-responsiveness account, (15) would come out true (see Section 4.1). However, on the risk-responsiveness account, (15) is false. On the risk-responsiveness model, actions that play the role of causally contributing to the group’s acquiring the belief that q can be actions individuals within the group are committed to, qua group members, that believe the target proposition (p). For example, part of what it is to be a member of a group that believes that p on the proposed account is to update the group’s epistemic position in connection with the practical circumstances in the manner suggested. And as I’ve suggested, such updates can play the role of psychological defeaters for the group’s continuing to believe the target proposition by acting as if it’s true in the way they had before.

What about Variation-2? With reference to the risk-responsive model of group belief, Variation-2 is structurally very closely akin to a undercutting psychological defeater for the group belief that the three scholarships merit award to A, B, and C (in that order). The rationale proceeds as follows. In Variation-2 the updated information, which Rebus (qua member of the group) made available to the group (via the central website) regarding Uriel’s unreliability very plausibly counts against the reliability of the mechanisms giving rise to the group’s relying on the group belief that the scholarships merit award in the order previously accepted, across the range of practical circumstances that they would have previously relied on it. In short, then, a proponent of (SEK-M) who insisted that, previously, group knowledge was present in the case, now has a story to tell for how that knowledge is defeated. Again, to the extent that knowledge is actionable (given present levels of practical risk), the group’s information state (following Rebus’s updates about Uriel) is not knowledge.[52]

6. Concluding Remarks

In conclusion, I hope to have illuminated a worrying, and thus far overlooked, weak spot which collective epistemologists have yet to adequately address. I’ve taken as a starting point a suggestion intimated by Lackey, which is that an ex ante constraint on any plausible account of group knowledge is that it be in principle defeated through ordinary mechanisms of epistemic defeat. Whereas Lackey has shown how Bird’s radical construal of socially extended knowledge fails this constraint, I’ve argued here that, given assumptions widely embraced in collective epistemology, the more moderate construal of the thesis faces just as much trouble. Though the central contribution here has been to raise this novel problem for the more moderate view, I’ve concluded by attempting to sketch a way forward. The way to accommodate epistemic defeat outlined in Section 6, granted, involves a number of commitments that proponents of group knowledge might not be amenable to. To the extent that they are not, it is incumbent upon proponents of group knowledge to find some alternative way to make sense of epistemic defeat. And to the extent that group knowledge is to be taken seriously, making sense of epistemic defeat is not a task that can be set aside.

Acknowledgments

Thanks to Olle Blomberg, Emma C. Gordon, Jesper Kallestrup, Jeroen de Ridder, Orestis Palermos, and Duncan Pritchard for helpful comments on earlier drafts. Thanks also to two anonymous referees at Ergo who offered a number of very helpful suggestions. This article was written as part of the AHRC-funded ’Extended Knowledge’ (AH/J011908/1) research project that is hosted by the University of Edinburgh’s Eidyn research centre.

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Notes

1. See, along with other recent and forthcoming papers, especially Lackey (2012; 2014). Lackey’s work on collective epistemology draws from recent work in individualist epistemology, in particular social epistemology. Her planned monograph The Epistemology of Groups is forthcoming with OUP.

2. For some sample comprehensive discussions of epistemic defeat, see especially Bergmann (1997), Lackey (1999; 2005), Pollock (1986). See also Sudduth (2008) for a contemporary overview.

3. Lackey’s argument from epistemic defeat is one of several arguments she offers against Bird’s account of (radically) socially extended knowing. Another key element in Lackey’s critique of Bird involves the relationship between knowledge and action. For the present purposes, I will be focusing entirely on her argument from defeat. Though it is important to keep in mind that Lackey’s argument against Bird does not rest entirely on the argument from defeat.

4. For a clear sense of the project of analyzing knowledge, understood along individual lines, see Ichikawa and Steup (2014).

5. For a comprehensive discussion of group knowledge attributions, see Lackey (2012).

6. For some approaches to group knowledge friendly to (SEK-M), see for instance Gilbert (1987; 2002; 2013), Knorr Cetina (2009), Mathiesen (2006), Tollefsen (2006), Tuomela (1995), Wray (2007).

7. One kind of case that proponents of distributed cognition are happy to embrace is Hutchins’s 1995 case of ship crew skillfully navigating an Iwo Jima class amphibious assault ship to port. On Hutchins’ view, the crew can know what no individual member knows.

8. Lackey (2014) herself uses a case of distributed cognition to make the point that (SEK-M) is a relatively standard view in collective epistemology. I follow her in using this case as demonstrative of (SEK-M). However, distributed-cognition-style cases aren’t needed to make the point. Consider, for example, the following case, which achieves the same result—viz., that a group can know something non of the individual members knows—with the strictures of a joint-commitment model.

   Committee: An art expert authentication committee has been called on to determine the veracity of a seller ’s claim that a particular pot dates to the late Jo¯ mon period (circa 300 AD). The committee is comprised of three members, A, B and C, each highly skilled in thermoluminescence, a dating method for archaeological pottery that is used to distinguish genuine from fake antiquities. The committee members adhere to strict professional and scientific norms and (after pooling all evidence) reach a clear group position: the pot is much older than expected. It dates to the early Jo¯ mon period (approximately 14,000 BC). All three committee members, however, are young earth Creationist and so, in a private capacity, each believes the earth, and thus the pot, is less than 6,000 years old.

   Provided that group knowledge involves group belief or acceptance (understood along joint-commitment lines) Committee is a case where the group, whose members adhere to the strictest scientific standards, knows something—that the pot dates to the early Jōmon period—even though each of its members fails to know because, due to their faith, each fails to believe the proposition in question.

9. While Lackey uses ‘aware’ to capture the laxity of the requirement, it’s important to note that she is not using awareness in the sense that if one is aware that p, then one knows that p—or else the radical view collapses into the moderate view. Rather, I think we could capture the spirit of Lackey’s attempt to characterize the position Bird is committing himself to by reading ‘not aware’ that p as ‘completely oblivious to’ p. As we’ll shortly see, Bird’s view allows group knowledge in cases where all individuals who had any clue about the item of knowledge in question had died. In this sense, these individuals were not aware of (and were completely oblivious to) p.

10. Here I am following Lackey’s (2014: 284–5) discussion of the key thrust of Bird’s p osition, which she challenges.

11. See Wray (2007: Section 4) for an argument against the claim that the scientific community, as a whole, can count as attaining collective knowledge, even if scientific research teams can possess collective knowledge.

12. Liberal, specifically, in the sense of what is epistemically tolerated of individuals in the group.

13. As Bird puts it, ‘it seems irrelevant that Dr. N. and others who had read the original paper had died or forgotten about it. What is relevant is that the discovery was in the public domain, available, through the normal channels, to anyone, such as Professor O., who needed it’ (Bird 2010: 32), cited also in (Lackey 2014: 284).

14. Perhaps Bird would object to the description of claim d as being ‘forgotten’ in this context. I am happy to replace this with ‘no longer present in human memory’.

15. There is perhaps some scope for Bird to object that a case like this will not play out in practice. To the extent that Dr. N’s published paper really is easily accessible by normal channels, then on the assumption that (as in the case of Addition) the scientific community really is very interested in matters connected to d, it’s implausible (given actual scientific standards) that no one would have come across d. Thanks to Olle Blomberg for discussion on this point.

16. Psychological defeaters are also referred to by some writers under the description of mental state defeaters. See Sudduth (2008).

17. Of course, there is some room to press back here. For one thing, it might not be as i mplausible as it would first seem to simply allow that scientific knowledge is not as extensive as we presume, while maintaining that this result would be compatible with insisting that everyday knowledge (of the sort that is of primary interest not to be ceded to the sceptic) is more or less what we thought. Lackey might rebut this point however by noting that, firstly, it’s an unacceptable sceptical concession to cede as much knowledge to the sceptic as we would by allowing scientific knowledge to be defeated so easily. Secondly, it’s plausible that there is some significant overlap between the scientific knowledge that would be ceded to the sceptic and everyday knowledge. Thanks to Duncan Pritchard for helpful discussion on this point.

18. A point of clarification. (SEK-R) is compatible with knowledge supervening on individuals’ mental states. At least, it’s not clear from Bird’s description of what must be present in cases of socially extended knowing that supervenience on mental states of individuals would be excluded in principle. The crux of the point Lackey is highlighting is that, at least in some cases, group knowledge can be present even when no individual’s mental state contributes to the group’s positive epistemic status. And so the arbitrariness charge should be best understood as restricted to cases where mental states do not, in fact, contribute positively to group knowledge, though they contribute negatively. Furthermore, there is scope to argue, contra Lackey, that it’s not true that individuals’ mental states do not contribute at all to the group knowledge that by (SEK-R) is claimed to be present in the Case of Dr. N. After all, the relevant discovery that was submitted into the scientific oeuvre was due to the intellectual efforts of Dr. N. Therefore, at least one individual’s mental states contribute (qua causal antecedent) to any group knowledge present later. Presumably, Lackey’s arbitrariness charge must reflect the worry that individuals’ mental states can contribute negatively to a group mental state that counts as knowledge at some time, t, even though, at t, no individual’s mental states are contributing positively toward that state.

19. Recall that (SEK-M), while allowing that a group can know that p even when no individual in the group knows that p, can permit epistemic requirements weaker than knowledge on individuals—requirements that individuals clearly do not meet while dead

20. See here especially Gilbert (1987; 2002; 2013). For an alternative non-summativist account of group belief, see the positional account of group beliefs as defended by Tuomela (1995).

21. As Mathiesen writes, capturing this idea, “in contexts where her group membership is salient she is committed to act, speak, and reason consistently with the group view. If she fails to do so, then she has violated an obligation she to has to her fellow group members.” (2006:196). Gilbert gives an illustrative example: “The members of a seminar on human rights may in the course of a meeting form a joint commitment to believe as a body that the notion of a group right is a viable one. This would involve a requirement to express that belief at least within the confines of the seminar when it is in session. More broadly, it would require that each party express that belief when acting as a member of the seminar ”(2004: 104)

22. Note that one can act as if p without positively believing oneself, in a private capacity, that p; believing not-p in a private capacity is not at conflict with joint commitment. As Gilbert says:

    One who participates in joint acceptance of p thereby accepts an obligation to do what he can to bring it about that any joint endeavors ... among the members of G be conducted on the assumption that p is true. He is entitled to expect others’ support in bringing this about ... if one does believe something that is inconsistent with p, one is required at least not to express that belief baldly. (1989: 306-7)

23. Lackey notes that this position is embraced by, among others, List and Pettit (2011: 64).

24. I am using this language in a way that is meant to be inclusive between rebutting and undercutting psychological defeaters, though to make things simple, I’ll be focusing on psychological defeaters of a rebutting variety.

25. What accepting p prohibits is acting, but acting in a way that is not as if p is true. Note that if one does nothing at all, one is not acting. I say this to clear up any confusion that the requirement that one act as if p is true implies the implausible result that one has to always be acting as if p is true in the sense that one must always be acting.

26. Consider an example in the individual case. Suppose I plan to place a bet on the Yankees-Braves game. I believe the Yankees will lose to the Braves and accordingly place a bet on the Braves. I then acquire a new belief to the effect that the entire Braves team has just acquired malaria, and no player can currently stand up, and act accordingly, by placing my bet on the Yankees. In doing so, I am no longer acting as if the Braves will win.

27. See Carter (2014).

28. Thanks to an anonymous referee at Ergo for comments that led to an improvement of this presentation.

29. To see why this is so, just consider that if I believe p at t₁, but stop believing p at t₂, and then acquire q which indicates not-p at t₃, my belief that q is not a psychological defeater for my belief that p, given that I no longer have a belief that p, at t₃, when I acquire q.

30. It is worth noting and replying to a potential line of objection. Suppose that S is part of an NGO that is trying to fight groups that argue that CO₂ doesn’t contribute to rising global temperature. Stipulate that S’s group has knowledge that CO₂ does contribute to rising global temperature. But as a consequence of S’s efforts to learn more about the arguments of the opponent groups (in order to rebut them), S acquires a belief that undermines some of the key data points that supported the group belief that CO₂ emissions drive a rise in global temperature. S takes this up for discussion in S’s group which collectively accepts that those data points are unreliable, and S’s group agrees not to rely on them in future. One might argue that this could be a psychological defeater of the group’s (previous) knowledge that CO₂ emissions cause rising global temperature, but yet, it is plausible that the group remains collectively committed to acting as if it is true that CO₂ emissions cause rising global temperature; the group simply takes it that not accepting the data points is compatible with this commitment. In response to this line, it is important to note that the devil is in the details of the case. If the data points in question are but a few data points among hundreds on which the NGO bases its collective belief that CO₂ contributes to rising temperatures, then not accepting the data points is indeed compatible with the commitment to act as if CO₂ emissions cause rising global temperature. Though in such a case it is implausible that the knowledge in question actually is defeated. Compare: in the individual case, if I base my belief that Team A will win on 100 items of information, and come to doubt 3, my overwhelming evidence that Team A will win remains. If, however, (in the NGO example) the data points in question were the three central data points on which the group based its belief that CO₂ emissions are present, then it is more plausible that knowledge would be defeated. However, in this variant of the case, it is no longer plausible to suppose that in acquiring the group belief that the data points are false, the group continues to retain its original belief that CO₂ contributes to rising temperatures. Thank you to Olle Blomberg for raising this objection.

31. For a discussion of differences between accepting and believing, at the individual level, see, for example, Engel (1998). Cf. Cohen (1992).

32. Proponents include Meijers (2002), Wray (2001) and Hakli (2007).

33. See also Wray (2007) for a defence of the view that research teams are candidates for (non-summativist) group knowledge understood as justified true acceptance. Wray however denies that such candidate collective knowers include communities of scientists identified with research fields.

34. Note that such a version of (SEK-M) is not committed to (JAB), which, in conjunction with (GMAP), was part of the original problem for (SEK-M).

35. Lackey discusses normative defeat in more detail in (among other places) Lackey (1999;2005).

36. For more on this distinction, see Raz (2009) and Olson (2009).

37. Cf. Cuneo: ”if reason R is an epistemic reason to believe that p, for S, then this is so regardless of whether S desires to believe the truth” (2007)

38. For a recent and very comprehensive discussion of this relationship, see Skorupski (2010).

39. Compare here Gilbert’s discussion of the obligation Jack has when jointly committing to walking with Jill. When Jack does something that’s not compatible with walking together—for instance, walking faster than will be reasonably possible for Jill to walk along side him—then Jill can rightly rebuke him. Plausibly, Jill then is released from any obligation she had to walk at a pace accommodating Jack. See Roth (2011: Section 4)

40. The kinds of φs I have in mind here will just be actions such that acting as if q involves these actions. Of course, some commitments one has, qua member of the group, can be commitments to do things other than actions, proper—e.g., commitments to be certain ways. This though is compatible with the point I’m making here, which relies just on the (GMAP) insight that the group can’t do anything without some individual acting.

41. Thanks to an anonymous referee at Ergo for pressing this line of reply.

42. To see how this would go, simply assume, for reductio, that for some group G, which accepts that p, G’s acceptance that p is, qua would-be knowledge, normatively defeated. If this were so, it would follow that there is a q such that group G (categorically) ought to accept q, where the truth of q counts against the truth of p or indicates p was unreliably formed or sustained. This much follows simply from (i) the definition of (group) normative defeat (GND-R), and (ii) the observation that the ought of normative defeat is the epistemic ought. Now, if we take seriously the idea that there is a q such that group G (categorically) ought to accept q, where the truth of q counts in some way against the truth of p, then it follows from (GMAP) that at least one member (M) ought to do some action, φ, that causally contributes to bringing it about that G accepts that q, where φ involves acting as if q. And now we’ve reached a variant of the same dilemma that emerges for the proponent of (SEK-R) who embraces (JAB). That is, what is the status of ‘M ought to φ’? If the ought in play is non-categorical, it is not the ought of normative defeat. If it is categorical, then this seems irreconcilable with the fact that any commitment M would have, qua member of the group G, to acting as if q (e.g., any commitment to φ) will always be conditional, in the sense, that M will, qua member of G, be only ever be committed to acting as if q provided others do.

43. See Carter (2014).

44. See also Meijers (2003) for some further defence of this rationale for rejectionism, in light of challenges from Gilbert (2002) and others.

45. And there will be some further premise here to the effect that gradience is the kind of property beliefs have essentially, if at all.

46. I am assuming that Stan counts as believing the proposition when his credence is .7. While this assumption is certainly friendly to a simple Lockean threshhold view of belief, where one counts as having a belief once one’s credence is sufficiently high, it’s not required in order to illustrate the point I am making here about the relationship between rational credence and rational action. All that point requires is that we assume he counts as believing in both cases, and that this is at least compatible with altering his credence from 1 to .7.

47. For a detailed discussion of such cases, and more generally of the connection between rational belief and rational action, see Carter et al. (in press).

48. To draw a parallel from the case of Stan, consider two extremes: in the first case, (and at one limit) we might jointly agree as a group to endorse p without qualification regarding just how we shall act as if p. At the other limit, we might agree to jointly accept (and thus act as if, and rely on) p, only if there is little to no practical risk to being wrong.

49. For a more detailed discussion of this kind of view, see Carter (2014).

50. See Hawthorne and Stanley (2008) for the most widely discussed version of this position.

51. Thanks to an anonymous referee at Ergo for suggesting this line be made explicit.

52. The reason the risk-responsiveness approach offers theoretical possibilities not available to the more traditional (JAB) model is structural. The same structural move made to make sense of psychological defeat can be exploited in a way that has promising resources for making sense, as well, of normative defeat. The most helpful way to think about this is to highlight, on the risk responsiveness model, that there are very different ways a group can act as if p. While individuals are conditionally committed to acting as if p in a qualified way (in a way that aligns with the circumstances of risk), the group itself is best understood as categorically committed to p, simpliciter. In this respect, the flexibility of the risk responsiveness approach prevents an individual within the group to be both categorically and non-categorically committed to the same action.