Permissivism, Underdetermination, and Evidence Elizabeth Jackson (Australian National University/Ryerson University) and Margaret Greta Turnbull (Gonzaga University) Forthcoming in the Routledge Handbook for the Philosophy of Evidence (please cite published version) Abstract: Permissivism is the thesis that, for some body of evidence and a proposition p, there is more than one rational doxastic attitude any agent with that evidence can take toward p. Proponents of uniqueness deny permissivism, maintaining that every body of evidence always determines a single rational doxastic attitude. In this paper, we explore the debate between permissivism and uniqueness about evidence, outlining some of the major arguments on each side. We then consider how permissivism can be understood as an underdetermination thesis, and show how this moves the debate forward in fruitful ways: in distinguishing between different types of permissivism, in dispelling classic objections to permissivism, and in shedding light on the relationship between permissivism and evidentialism. Keywords: Permissivism; Uniqueness; Evidentialism; Epistemic Rationality; Underdetermination; Theory Choice; Disagreement; Evidential Support 1. Introduction Permissivism is the thesis that some bodies of evidence permit more than one rational doxastic attitude toward a particular proposition.1 In this chapter, we provide a new way of thinking about permissivism and show that this way of conceiving of permissivism dispels some classic objections to permissivism. It also helps us to better understand the relationship between permissivism and evidentialism, the thesis that says that justified belief supervenes only on one's body of evidence. To better appreciate permissivism, we propose, one should think about permissivism as a kind of underdetermination thesis. Before proceeding, we clarify the permissivist thesis and the various forms it may take. In Section 2, we explain why the truth of permissivism matters to other debates, such as disagreement and doxastic voluntarism. Then, we canvas some of the prominent arguments for and against permissivism in Section 3. In Section 4, we argue that thinking about permissivism as an underdetermination thesis can strengthen the case for permissivism and reveal how permissivism and evidentialism are connected. Permissivism is a thesis about bodies of evidence and the rational doxastic attitudes which individuals can hold towards them. The denial of permissivism is uniqueness, the thesis that there is at most one rational doxastic attitude toward a proposition, given a body of evidence.2 Of first importance, note that uniqueness is a universal claim, whereas permissivism is an existential claim; permissivism does not entail that, for all bodies of evidence and propositions, more than one 1 We are primarily interested in versions of permissivism which focus on the rational doxastic attitudes that are adopted in response to a body of evidence, rather than the proposition(s) which that body of evidence supports. See Titelbaum and Kopec for discussion of how the attitudinal form of uniqueness, the denial of permissivism, relates to the propositional form of uniqueness (2019: 206-7). 2 This is Feldman's (2007: 205) version of uniqueness which allows for the possibility that for some bodies of evidence, there many not be even one doxastic attitude which can be rationally adopted towards them. 2 doxastic attitude can rationally be held. It merely entails that there exist some permissive bodies of evidence and makes no claim about which bodies of evidence are permissive. Second, the doxastic attitudes in question can include both degreed attitudes, including credences, and full or coarse-grained doxastic attitudes, such as belief, disbelief, and suspension of judgment.3 Credal Permissivism states that for a body of evidence and a proposition p, there is more than one credence in p that can be rationally held; Belief Permissivism is the thesis that a body of evidence and a proposition p, there is more than one belief-attitude in p that can be rationally held.4 But who are the individuals who hold these doxastic attitudes towards bodies of evidence of importance to permissivism? Importantly, permissivism might be taken to be the thesis that it could be rational for a single individual to hold more than one doxastic attitude towards a body of evidence or to be the thesis that distinct individuals can each hold different rational doxastic attitudes towards a body of evidence.5 Intrapersonal Permissivism says that for some bodies of evidence, there is more than one doxastic attitude which can rationally be held by a single individual. According to Interpersonal Permissivism, in some cases, different individuals who share evidence may rationally hold their own, distinct doxastic attitudes in response to their evidence. Finally, there is temporal component latent within permissivism. Diachronic Permissivism states that at different times, it can be rational for an individual (or different individuals) to hold different doxastic attitudes in response to a body of evidence. Since permissivism is a thesis about a single, static body of evidence, this body of evidence would not change over time. Synchronic Permissivism, on the other hand, says that it can be rational for an individual (or different individuals) to hold different doxastic attitudes in response to a body of evidence at the same time. These versions of permissivism can be combined symbiotically. For example, many authors interested in the possibility of rational disagreement among those who share evidence are usually interested in Synchronic Interpersonal Permissivism, the thesis that different individuals may rationally hold different doxastic attitudes in response to a body of evidence at the same time.6 Jackson (forthcoming) and Podgorski (2016) defend Diachronic Intrapersonal Belief Permissivism, the thesis at a single individual may rationally hold different belief-attitudes toward a proposition at different times in response to a body of evidence. It's widely recognized that you can consistently affirm certain versions of permissivism while denying others. For example, those that affirm Diachronic Intrapersonal Belief Permissivism may reject Synchronic Interpersonal Belief Permissivism. Or one might affirm Credal Permissivism but deny Belief Permissivism. Some arguments for and against permissivism rely on a central idea which unites many forms of permissivism, the idea that there are multiple ways to rationally assess the deliverances of a body of evidence. Other arguments concerning permissivism apply only to specific versions of permissivism, 3 One might also include fuzzy, imprecise, or interval credences; see Kelly (2013) and Jackson (2019). 4 Many discussions of permissivism focus on the coarse-grained forms of the thesis, but there has been recent renewed interest in credal forms, including Horowitz (2013), Levinstein (2017), Schoenfield (2018), Schultheis (2018), and Jackson (2019). 5 See Kopec and Titelbaum (2016: 191) for further discussion of this distinction as it applies to denial of permissivism, uniqueness. 6 This includes Ballantyne & Coffman (2011; 2012), Christensen (2016), Schoenfield (2014), and Weintraub (2013). 3 which we detail in the third section. Consequently, identifying which form of permissivism one is interested in is crucial to determining what argumentative burdens one shoulders. Before proceeding to arguments for and against permissivism, we explain why permissivism matters to epistemologists as well as to non-philosophers. 2. What's At Stake One might wonder why the dispute over permissivism and uniqueness is significant; what hangs on it, and why should we care whether bodies of evidence can be permissive? First and foremost, determining whether permissivism is true can help us to better understand the nature of evidence and the connection between evidence and epistemic rationality.7 Whether evidence can, in some cases, be permissive is crucial for answering questions central to this volume, i.e. questions about what evidence is like. Further, permissivism has noteworthy implications for the epistemology of disagreement. Disagreement, especially disagreement among epistemic peers--epistemic equals, who share the same evidence and reliability--raises questions about belief revision.8 Specifically: are you required to change your doxastic attitudes (e.g. withhold belief or be less confident) upon encountering a disagreeing peer? Some, such as Christensen (2007; 2009), say yes: holding to your previous attitude seems dogmatic and close-minded. Others, such as Kelly (2005), say no: disagreement in and of itself doesn't give us reason to revise our beliefs, and there are many intuitive cases of reasonable disagreement. For instance, jurors share evidence but seem to rationally disagree about who is guilty (see Rosen 2001).9 If Interpersonal Permissivism is true, then you and your peer can share evidence but come to different conclusions on some matter without compromising rationality. Thus, even if you have many disagreeing peers, on a permissive picture, you may not be required to change your doxastic attitudes on pains of irrationality.10 Further, if one were convinced that reasonable disagreement is possible and that permissivism can explain reasonable disagreement, this might provide an abductive argument for permissivism.11 No matter how one lands on these controversial issues, though, it should be clear that there are crucial connections between permissivism and disagreement. The implications of permissivism go beyond disagreement. For instance, consider the basic question in the doxastic voluntarism debate: can we ever have direct control over our beliefs? The traditional answer is no, we cannot control our beliefs directly; e.g. no matter how much money you offer me, I 7 See Ballantyne and Coffman (2011). 8 There are differing, incompatible definitions of epistemic peer in the literature; see Kelly (2005) and Elga (2007: 487). 9 Although White (2005) argues that many jurors might not actually share evidence. See also Greco and Hedden (2016). 10 Rationally remaining steadfast in spite of disagreement may additionally require known permissivism to be true: that we can know, at least sometimes, when our evidence is permissive. For discussion of known permissivism, see White (2005), Ballantyne and Coffman (2012), and Cohen (2013). 11 However, Lee (2013), Levinstein (2015), and Christensen (2016), argue that peer disagreement might require belief revision even if permissivism is true. 4 cannot make myself believe that 2+2=5.12 However, recently, some have pointed out that most of the arguments for doxastic involuntarism assume that uniqueness is true; of course, I cannot make myself believe 2+2=5, because it is clear that my evidence determines one unique doxastic attitude toward that proposition. If permissivism is true, and I find myself in a permissive case with respect to some proposition, such that two rational doxastic attitudes are "live" for me at once, it is much less clear that the standard arguments for doxastic involuntarism are successful.13 While we don't have space to fill out all the connections in detail here, we simply note that permissivism has key implications for debates in both epistemology and philosophy of mind. 3. Permissivism: For and Against Not all philosophers find permissivism plausible.14 Concerns about permissivism range from its consequences for how we understand evidential support to its implications for metaepistemology. In this section, we survey some prominent arguments against permissivism, and then consider some positive arguments for permissivism. Since arguments for and against permissivism often focus on Belief Permissivism, we will discuss them as they apply to belief, but note that most of these arguments also apply to Credal Permissivism. 3.1 Arguments Against Permissivism Some critics find permissivism to be implausible given intuitions about the relationship between evidence and proposition. These philosophers argue that it is intuitive that a body of evidence objectively only supports one doxastic attitude towards a proposition, in keeping with the thesis of uniqueness (Feldman 2007: 231). Feldman, Matheson (2011: 365), White (2005: 447), and others indicate that for every body of evidence, there is an objective fact about what that body of evidence, considered as a whole, supports. Individuals may fail to track these facts about evidential support in their choice of doxastic attitudes given their fallibility, and their consistent tendency to fail to match their doxastic attitudes to the objective support of evidence to a proposition renders this failure irrational. These arguments conclude that since evidence objectively supports at most one doxastic attitude toward a proposition, permissivism is false. Others have argued that Intrapersonal Permissivism infuses the choice of which doxastic attitudes to adopt with a level of arbitrariness.15 White considers Extreme Permissivism, the view that in some cases it can be rational to believe p or to believe ~p in response to a body of evidence (2005: 447). White suggests that if my evidence allows me to rationally believe p or to believe ~p, then what I believe will not be appropriately connected to truth (2005: 448). So whether I end up believing p or end up believing ~p will be determined by "some arbitrary factor," presumably one which is not relevant to the truth of p (2005: 447-8). 12 Arguments for doxastic involuntarism include Alston (1989), Bennett (1990), Hieronymi (2009). 13 Those that draw this connection between permissivism and doxastic voluntarism include Raz (1999: 9), Ginet (2001), Frankish (2007), Nickel (2010), McHugh (2014), Roeber (forthcoming-a, forthcoming-b), and Jackson (forthcoming). Also see Sylvan (2016) and Steup (2017: sections 3-5). 14 See Ballantyne (2018) for a critical discussion of the cases which are commonly taken to given intuitive plausibility to permissivism. 15 Stapleford (2018) more recently defends this line of objection to permissivism. 5 Concerns about arbitrariness lead us to a second objection to Intrapersonal Permissivism, which holds that Intrapersonal Permissivism implausibly allows individuals to "toggle" between doxastic attitudes. If one's evidence equally supports believing p or ~p or equally supports believing p or suspending judgment in p, then it seems that an individual is permitted to switch between these doxastic attitudes towards p at will, "toggling" between the rationally permitted doxastic attitudes as it suits them. As White puts it, "if I really do judge that believing P in this situation would be rational, as would believing not-P, then there should be nothing wrong with my bringing it about that I have some belief or other on the matter" (2005: 449). The apparent sanctioning of toggling casts implausibility on Intrapersonal Permissivism. It seems blatantly wrong to suggest that it can be rational for individuals to adopt p at one time point and adopt ~p at another time in response to a static body of evidence without some change, such as the addition of some new piece of evidence, prompting that toggling. Recently, some critics of permissivism have raised metaepistemological concerns about the value of rationality on a permissive picture. These critiques, including those found in Horowitz (2013), Dogramaci and Horowitz (2016), Greco and Hedden (2016), and Levinstein (2017), have a common thread, which they share with White's (2005) original criticisms. These authors assume that rationality is of value to individuals in so far as it provides us the best route to accurate beliefs (or credences). But according to permissivism, there sometimes exists more than one rational doxastic attitude toward p that can be held in response to a body of evidence. For example, on Extreme Belief Permissivism, where a body evidence permits belief that p and belief that ~p, you can be rationally permitted to hold at least one attitude you know to be false. This common motivation behind metaepistemological critiques holds that permissivism threatens the value of rationality in so far as it severs rational beliefs/credences from their assumed connection to accuracy. Finally, recent worries have been raised about the form of Credal Permissivism which states that any credence within a specific interval can be rationally adopted in response to a body of evidence (Schultheis 2018). 3.2 Arguments For Permissivism Permissivists have a ready response to the criticism that permissivism involves denying objective facts about what a body of evidence supports. Instead of conceiving of the relationship between evidence and proposition as a two-place relation, many permissivists argue that evidence relates to propositions via a three-place relation. We learn what a body of evidence supports, state these permissivists, by applying a set of epistemic standards (see especially Schoenfield 2014), such as a particular weighting of the opposing Jamesian goals of believing truths and avoiding error (see Kelly 2013), or a trade off between simplicity or explanatory power.16 If I prize believing truth over believing error and you weight these goals differently, or if we otherwise interpret evidence with different epistemic standards, then permissivists argue we will quite naturally arrive at distinct, rational doxastic attitudes in response to the same body of evidence.17 Numerous authors have also noted that orthodox subjective Bayesianism is interpersonally permissive, since there exist multiple sets of priors which can be held by rational agents.18 When individuals begin with different prior probability distributions, they will end up with different credences, even after conditionalizing on the 16 See also Titelbaum (2010), Decker (2012), Nolan (2014), Rubin (2015), and Weisberg (forthcoming). 17 But see Horowitz (2018) in response. 18 See Douven (2009), Meacham (2013), Kelly (2013: 305, 308), Weintraub (2013: 745), and Kopec and Titelbaum (2016: 192). See White (2010) for an argument against this on the basis of indifference principles. 6 same evidence.19 According to these permissivists, evidence just doesn't objectively support a proposition on its own; it supports a proposition relative to how we interpret or weigh that evidence or the prior probability distributions we originally hold. Since individuals can rationally differ in how they interpret and weigh their evidence, argue permissivists, they can rationally hold distinct doxastic attitudes in response to the same body of evidence. Invoking the three-place relation also helps explain why permissivists aren't saddled with arbitrariness. If my weighting of the Jamesian goals leads me to believe p, and your weighting of the Jamesian goals leads you to believe ~p, it will be entirely epistemic considerations which determine which doxastic attitude either of us holds. No arbitrary factor need be invoked to explain why I believe p and you believe ~p in response to a single body of evidence. We will offer our own response to the toggling objection in the final section, but note that there are extant responses to from Brueckner and Bundy (2012), Podgorski (2016), and Jackson (forthcoming). Permissivists have also offered responses to metaepistemological worries about the value of rationality on permissivism. Miriam Schoenfield (forthcoming) argues that it is harder for adherents of uniqueness to account for the value of rationality than permissivists if we want to maintain internalism about justification and the recognition that "it is sometimes rational to be uncertain about which doxastic states are rational given a body of evidence" (forthcoming: 1). Thorstad (forthcoming) provides two different permissivist metaepistemologies, countering the implication that permissivism is incompatible with robust understandings of the value of rationality. Meacham (2019) responds to metaepistemological objections to permissivism that arise on the basis of deference principles, principles that tell us when we should adopt the beliefs of those around us. Finally, some permissivists have provided arguments that specific types of beliefs are permissive, including beliefs which are true only if we believe them (Raleigh 2015; 2016, Kopec 2015, Dahlback forthcoming). We've outlined reasons one should care about the permissivism debate (Section 2) and have provided a general overview of challenges to and defenses of permissivism (Section 3). Now, we'll proceed to argue that thinking about permissivism as a kind of underdetermination thesis, a thesis about how our evidence fails to determine which doxastic attitude we should adopt, can help us to make progress in seeing why permissivism is plausible as well as how it relates to evidentialism about justification. 4. Permissivism, Underdetermination, and Evidentialism 4.1 Permissivism and Underdetermination The underdetermination of theory by evidence is a familiar phenomenon in the philosophy of science.20 In the philosophy of science literature, when theory is underdetermined by evidence, a body of evidence (whether it is all the evidence we could ever obtain or merely the evidence we 19 Although given some assumptions, formal results show that, with a sufficient amount of time and enough shared observations, their credences will eventually converge. See Doob (1971), Gaifman and Snir (1982), Hawthorne (1994). 20 There are several motivations for the idea that scientific theories are underdetermined, including the Duhem-Quine thesis, which states that it is impossible to test a scientific theory in isolation, because of the background assumptions required in order to test a hypothesis. 7 presently have access to) does not determine whether a scientist should believe some theory.21 For instance, the Stegosaurus, a species of dinosaur, has bizarre spikes and plates on its spine. Paleobiologists disagree about the function of these spikes: some believe they had a thermoregulatory purpose; others argue the spikes were a defense mechanism, while others insist that their function was to help the dinosaurs recognize each other. Each group shares the same body of evidence, but nonetheless believes a different theory, and we have no reason to think that advocates of these different theories are believing irrationally.22 In this, familiar cases of scientific underdetermination appear to be cases where evidence is epistemically permissive. Permissivism and underdetermination are both concerned with bodies of evidence which do not necessarily lead rational agents to the same conclusion. We return to the relationship between scientific practice and permissivism in the next subsection. First, we note a distinction that is crucial for our later discussion. Upon considering permissivism as an underdetermination thesis, one of the first things to consider is the way the permissivism debate centers around evidence. All it takes to be a permissivist is to affirm that in some cases, a body of evidence underdetermines what one can rationally conclude, given that evidence. Note that this does not mean that what attitude one ought to take is ever fully underdetermined. It might be that the facts about one's epistemic situation that go beyond one's evidence, like one's epistemic standards or auxiliary assumptions, always determine one rational attitude. Even if one's choice of doxastic attitude is underdetermined by the evidence, it may not be underdetermined in general. This leads to a crucial distinction between two specifications of permissivism: Evidence-Underdetermination Permissivism: in some cases, a body of evidence underdetermines a particular rational doxastic attitude toward p. Full-Underdetermination Permissivism: in some cases, all potentially relevant facts about a particular epistemic situation underdetermine a particular rational doxastic attitude toward p.23 Evidence-Underdetermination Permissivism is the minimal permissivist thesis. FullUnderdetermination Permissivism, on the other hand, is a much stronger thesis, and is more controversial in epistemology (and in related discussions in the philosophy of science). FullUnderdetermination Permissivism requires that, at least in some cases, the doxastic attitude one ought to hold is underdetermined in general, not just by evidence, but by anything that might be potentially relevant to what attitude one ought to have, including one's auxiliary assumptions, one's epistemic standards and values, one's interpretation of the evidence, one's weighting of the Jamesian goals, what is salient for that person, what is at stake for that person, etc. On this way of mapping out the territory, Full-Underdetermination Permissivism entails Evidence-Underdetermination Permissivism, but not vice versa. Note that because the permissivism debate is focused on evidence, one need not affirm FullUnderdetermination Permissivism in order to be a permissivist. Permissivism is consistent with the 21 See Stanford (2017) and Turnbull (2017) for surveys of the literature on underdetermination in scientific contexts. Others who discuss underdetermination in epistemology include Bates (2004), Bird (2007), and Callahan (MS). 22 This example is from Turnbull (2017: 7). 23 See Laudan (1990) for discussion of this kind of underdetermination in scientific contexts. 8 claim that all rational doxastic attitudes could be completely determined, in every situation-the permissivist would just hold that they aren't determined by evidence alone, but by other factors. For example, what doxastic attitude I ought to have might be fully determined in every situation by the conjunction of my evidence and my epistemic standards. In a scientific context, it might be determined by my evidence and my auxiliary assumptions. No two doxastic attitudes are ever "live" for me at the same time; what attitude I ought to hold is fully determined, but not by merely my evidence (See Podgorski 2016, and Jackson forthcoming). Evidence-Underdetermination Permissivism, is a weaker claim; it doesn't commit one to any kind of general underdetermination, but merely underdetermination by evidence. 4.2 Strengthening the Case for Permissivism There are several ways that understanding epistemic permissivism as an underdetermination thesis makes the case for permissivism stronger. Given that Evidence-Underdetermination Permissivism is an existential claim, we need only one extant body of evidence that fails to determine a single rational attitude for it to be true. And it is widely accepted by philosophers of science that, in some scientific contexts, our current evidence doesn't determine a single rational attitude. Biddle (2013: 125), following Kitcher (2001), distinguishes between two underdetermination theses. The first, which he calls "global underdetermination," states that "all theories (or hypotheses, models, etc.) are underdetermined by... all possible evidence."24 Biddle notes that global underdetermination is controversial, and a number of philosophers of science call it into question.25 The epistemic counterpart of this thesis would be the claim that all bodies of evidence permit more than one attitude toward all propositions, which equally seems like a strong (and probably implausible) thesis. The second thesis Biddle calls "transient underdetermination" (2013: 125). This thesis states that "some theories, hypotheses, and models are underdetermined by... the currently available evidence" (2013: 125). This thesis corresponds to the basic evidence-underdetermination permissivist claim, that, in some cases, the currently available evidence leaves open more than one rational response to a proposition. When considering this second thesis, Biddle remarks, "This thesis, moreover, is undoubtedly true" (125). Biddle also notes that Kitcher maintains that transient underdetermination is "familiar and unthreatening" (Kitcher 2001: 30, qtd. in Biddle 2013: 125). We find cases of transient underdetermination at the edges of scientific investigation. As we encounter new data and advance new hypotheses to account for this data, the evidence available to us doesn't indicate which hypothesis scientists should believe. For example, Biddle discusses cases of underdetermination encountered in experiments on the carcinogenic effects of dioxins and Turnbull examines a case of underdetermination in contemporary dinosaur paleobiology (Biddle 2013: 126 and Turnbull 2017: 7). Cases of transient underdetermination like these are seen as uncontroversial by philosophers of science. This should give epistemologists pause, and make one consider whether they've have been neglecting some obvious permissive cases from the scientific realm. 24 See Quine (1951) and Duhem (1962). 25 Including Laudan and Leplin (1991) and Norton (2008). 9 The second way that connecting permissivism and underdetermination strengthens the case for permissivism is that it clarifies how one might respond to some classic objections to permissivism. Consider, for instance, Roger White's toggling objection, discussed in Section 2: if a body of evidence permits more than one attitude, then what prevents a rational agent from randomly moving in between the permitted attitudes? White notes, "Each time I toggle my beliefs in this manner I am relieved to find that my resulting opinion is true. The absurdity of this should make us wonder whether permissive cases are possible" (2013: 317). Random toggling between attitudes like this seems epistemically irrational, but it is initially unclear the permissivist has the resources to explain why (White 2005, 2013, Hedden 2015). The distinction above, between Evidence-Underdetermination Permissivism (what attitude one should have is underdetermined by one's evidence) and Full-Underdetermination Permissivism (what attitude one should have is underdetermined by all relevant epistemic facts) helps us see a new way that permissivists can answer White's objection. White's worry only applies to FullUnderdetermination Permissivism, but not to Evidence-Underdetermination Permissivism. It might be that at a time, the facts about your epistemic situation fully determine a rational doxastic attitude (even though your evidence does not). Toggling is not permissible for you, even though you are in a permissive case, because what you ought to believe is fully determined--just not by your evidence alone. Because two attitudes are never epistemically "live" for you at a particular time, you cannot toggle between them. This response to toggling relates to some of the existing responses to White, but enable us to frame the response more generally. Take, for instance, Schoenfield (2014)'s response to White: the permissivist can explain why toggling is impermissible if rational attitudes are a function of both one's evidence and one's epistemic standards. On a natural reading of Schoenfield's view, she is committing to Evidence-Underdetermination Permissivism but denying Full-Underdetermination Permissivism. Toggling is irrational because one's evidence plus one's standards determine a particular rational attitude, and this is perfectly consistent with Evidence-Underdetermination Permissivism. Other responses to toggling vary what this third factor might be--for instance, it could be a different weighing of Jamesian goals (Kelly 2013), practical stakes (Rubin 2015), or what is salient for a person (Jackson forthcoming). Understanding permissivism as an underdetermination thesis helps us see what unites these responses (their commitment to Evidence-Underdetermination Permissivism and appeal to a third determining factor, resulting in the denial of FullUnderdetermination Permissivism), and provides a general strategy for identifying versions of permissivism that are immune to the toggling worry. 4.3 Permissivism and Evidentialism Finally, we consider how underdetermination might shed light on the relationship between permissivism and evidentialism. Evidentialism is a thesis about what doxastic attitudes one (epistemically) ought to have; Earl Conee and Richard Feldman (1985: 15) define evidentialism as the view that "justified attitudes are determined entirely by the person's evidence." Following Conee and Feldman, we adopt the following definition of evidentialism: Evidentialism: which doxastic attitude S epistemically ought to have supervenes only on S's evidence. 10 In other words, the only thing that speaks to which attitudes or opinions one should have is one's evidence.26 Our previous discussion of the relationship between permissivism and underdetermination has noteworthy implications for the evidentialist. The first is why and how evidentialism and permissivism are consistent. Combining permissivism and evidentialism requires one accept Full-Underdetermination Permissivism; that is, in cases where more than one attitude toward p is permitted by one's evidence, no other factor besides evidence can play into what attitude one ought to have. Thus, if evidentialism and permissivism are both true, there must be cases in which one's rational attitude is fully underdetermined. In this, permissivists can be evidentialists, although as a (perhaps contingent) matter of fact, many evidentialists (e.g. Feldman) happen to endorse uniqueness. But nothing about the permissivist claim itself forces this; permissivism and evidentialism are perfectly consistent. Hence, those who accept both permissivism and evidentialism must commit to this strong version of underdetermination. This is not necessarily an unhappy consequence, but it does requires permissive evidentialists to adopt a new response to the toggling objection. While there are a number of responses to toggling present in the literature, many are specific instances of the general schema we present above: a denial of Full-Underdetermination Permissivism and acceptance of Evidence-Underdetermination Permissivism; some other factor, in addition to evidence, keeps one tied to a particular attitude, such that toggling is impermissible.27 Evidentialists cannot appeal to these extra-evidential factors to respond to toggling. But this does not mean that toggling is devastating for the permissive evidentialist. Instead, the evidentialist could argue, e.g., that toggling is practically, but not epistemically impermissible, in the same way that, when deciding which to use to eat one's cereal, toggling between two spoons is (in some sense) impermissible. There's nothing that gives one attitude an epistemic advantage over the other, but one has strong practical reason not to switch back and forth.28 No matter where the permissivist evidentialist lands on this matter, we conclude that permissivism and evidentialism are consistent. While this combination of views might present unique challenges, it is far from clear that they are insurmountable. 5. Conclusion We introduced the debate between epistemic permissivism and uniqueness and explained why this debate has broad significance. Then, we outlined arguments, objections, and replies for each side. Finally, we've argued that understanding permissivism as a underdetermination thesis is fruitful in distinguishing between different versions of permissivism, responding to objections to permissivism, and understanding the relationship between permissivism and evidentialism. 26 Of course, this raises many questions, such as "what is evidence?" and "what is it for a person to have evidence?" These questions go beyond the scope of this paper. For more detailed discussions of these questions and other matters related to evidentialism, including arguments for and against, see Conee and Feldman (1985, 2004) and McCain (2014, 2018). 27 See Kelly (2013) and Schoenfield (2014). 28 This response is developed in Roeber (forthcoming-a). See also Callahan (MS). 11 Acknowledgements: Both authors contributed equally to this article, and were equally involved in every stage of its conception and writing. Thanks to Giada Fratantonio, Maria Lasonen-Aarnio, Clayton Littlejohn, Sam Murray, Sam Hall, Manuela Fernandez-Pinto, Nathan Mueller, and the audience at the 2018 open-mindedness conference at Weatherford College. Works Cited Alston, W. (1989). Epistemic Justification: Essays in the Theory of Knowledge. Ithaca, NY: Cornell University Press. Ballantyne, N. (2018). Is Epistemic Permissivism Intuitive? American Philosophical Quarterly, 55(4), 365-378. Ballantyne, N. & Coffman, E.J. (2011). Uniqueness, Evidence, and Rationality. Philosophers' Imprint, 11, 1-13. Ballantyne, N. & Coffman, E.J. (2012). Conciliationism and Uniqueness. Australasian Journal of Philosophy, 90(4), 657-670. Bates, J. (2004). Reflective Equilibrium and Underdetermination in Epistemology. Acta Analytica, 19(32), 45-64. Bennett, J. (1990). Why is Belief Involuntary? Analysis, 50(2), 87-107. Biddle, J. (2013). State of the Field: Transient Underdetermination and Values in Science. Studies in History and Philosophy of Science Part A, 44(1), 124-133. Bird, A. (2007). Underdetermination and Evidence. In Bradley John Monton (Ed.), Images of Empiricism: Essays on Science and Stances, with a Reply From Bas C. Van Fraassen. Oxford: Oxford University Press Brueckner, A. & Bundy, A. (2012). On "Epistemic Permissiveness." Synthese 188(2), 165-177. Callahan, L. (MS). "Epistemic Underdetermination." Christensen, D. (2007). Epistemology of Disagreement: The Good News. Philosophical Review, 116(2), 187-217. Christensen, D. (2009). Disagreement as Evidence: The Epistemology of Controversy. Philosophy Compass, 4(5), 756-767. Christensen, D. (2016). Conciliation, Uniqueness, and Rational Toxicity. Noûs, 50(3), 584-603. Cohen, S. (2013). A Defense of the (Almost) Equal Weight View. In David Christensen and Jennifer Lackey (Eds.), The Epistemology of Disagreement: New Essays (pp. 98-120). New York: Oxford University Press. Feldman, R. and Conee, E. (1985). Evidentialism. Philosophical Studies, 48(1), 15-34. Conee, E. and Feldman, R.(2004). Evidentialism. Oxford: Oxford University Press. Dahlback, M. (forthcoming). Infinitely Permissive. Erkenntnis. Available at: https://www.academia.edu/20402399/Infinitely_Permissive. Decker, J. (2012). Disagreement, Evidence, and Agnosticism. Synthese, 187(2), 753-783. Dogramaci, S. and Horowitz, S. (2016). An Argument for Uniqueness about Evidential Support. Philosophical Issues, 26(1), 130-147. Doob, J. L. (1971). What is a Martingale? The American Mathematical Monthly, 78(5), 451-463. Douven, I. (2009). Uniqueness Revisited. American Philosophical Quarterly, 46(4) 347-361. Duhem, P. (1962). The Aim and Structure of Physical Theory. Trans. P. Wiener. New York: Atheneum. Elga, A. (2007). Reflection and Disagreement. Noûs, 41(3), 478-502. Feldman, R. (2007). Reasonable Religious Disagreements. In Louise M. Antony (Ed.), Philosophers Without Gods: Meditations on Atheism and the Secular Life (pp. 194-214). New York: Oxford University Press. 12 Frankish, K. (2007). Deciding to Believe Again. Mind, 116(2), 523-47. Gaifman, H. and Snir, M. (1982). Probabilities Over Rich Languages, Testing and Randomness. The Journal of Symbolic Logic, 47(3), 495-548. Ginet, C. (2001). Deciding to Believe. In M. Steup (Ed.), Knowledge, Truth, and Duty. Oxford: Oxford University Press). Greco, D. and Hedden, B. (2016). Uniqueness and Metaepistemology. Journal of Philosophy, 113(8), 365-395. Hawthorne, J. (1994). On the Nature of Bayesian Convergence. PSA: Proceedings of the Biennial Meeting of the Philosophy of Science Association, 1994, 241-249. Hedden, B. (2015). Time-Slice Rationality. Mind, 124(494), 449-491. Hieronymi, P. (2009). Believing at Will. Canadian Journal of Philosophy, 35, 49-87. Horowitz, S. (2013). Immoderately Rational. Philosophical Studies, 167, 41-56. Horowitz. S. (2018). Epistemic Values and the "Jamesian Goals." In Jeffrey Dunn and Kristoffer Ahlstrom-Vij (Eds.), Epistemic Consequentialism. New York: Oxford University Press. Jackson, E. (2019). Belief and Credence: Why the Attitude-Type Matters. Philosophical Studies. 176(9): 2477-2496. Jackson, E. (forthcoming). A Defense of Intrapersonal Belief Permissivism. Episteme. DOI: https://doi.org/10.1017/epi.2019.19. Kelly, T. (2005). The Epistemic Significance of Disagreement. In John Hawthorne and Tamar Gendler (Eds.), Oxford Studies in Epistemology (Vol. 1, pp. 167-196). New York: Oxford University Press. Kelly, T. (2013). Evidence Can Be Permissive. In Ernest Sosa and John Turri (Eds.), Contemporary Debates in Epistemology (2nd Edition, pp. 305-311). Hoboken, NJ: Wiley Blackwell. Kitcher, P. (2001). Science, Truth, and Democracy. New York: Oxford University Press. Kopec, M. (2015). A Counterexample to the Uniqueness Thesis. Philosophia, 43, 403–9. Kopec, M. & Titelbaum, M. (2016). The Uniqueness Thesis. Philosophy Compass, 11(4), 189-200. Laudan, L. (1990). Demystifying Underdetermination. In C.W. Savage (Ed.), Scientific Theories, Minnesota Studies in the Philosophy of Science (Vol. 14, pp. 267-297). Minneapolis: University of Minnesota Press. Laudan L. & Leplin, J. (1991). Empirical Equivalence and Underdetermination. The Journal of Philosophy, 88, 449-472. Lee, M. (2013). Conciliationism Without Uniqueness. Grazer Philosophische Studien, 88, 161–88. Levinstein, B. (2015). With All Due Respect: The Macro-Epistemology of Disagreement. Philosophers' Imprint 15(13): 1-20. Levinstein, B. (2017). Permissive Rationality and Sensitivity. Philosophy and Phenomenological Research, 94(2), 342-370. Matheson, J. (2011). The Case for Rational Uniqueness. Logos and Episteme, 2(3), 359-373. McCain, K. (2014). Evidentialism and Epistemic Justification. New York: Routledge. McCain, K. (2018). Believing in Accord with the Evidence: New Essays on Evidentialism. Springer. McHugh, Conor. (2014). Exercising Doxastic Freedom. Philosophy and Phenomenological Research, 88(1), 1-37. Meacham, C. (2013). Impermissive Bayesianism. Erkenntnis, 79 (S6), 1185-1217. Meacham, C. (2019). Deference and Uniqueness. Philosophical Studies, 176(3), 709-732. Nickel, P. (2010). Voluntary Belief on a Reasonable Basis. Philosophy and Phenomenological Research, 81(2), 312-34. Nolan, D. (2014). "Dangers of Pragmatic Virtue," in Inquiry, 57(5-6), 623-644. 13 Norton, J. (2008). Must Evidence Underdetermine Theory? In Martin Carrier, Don Howard, and Janet Kourany (Eds.), The Challenge of the Social and the Pressure of Practice: Science and Values Revisited (pp. 17-44). Pittsburgh: University of Pittsburgh Press. Podgorski, A. (2016). Dynamic Permissivism. Philosophical Studies, 173(7), 1923-1939. Quine, W. V. O. (1951). Two Dogmas of Empiricism. The Philosophical Review. 60, 20-43. Raleigh, T. (2015). "An Argument for Permissivism from Safespots. In W. van der Hoek et al (Eds.) Logic, Rationality, and Interaction (pp. 308–15) . Berlin Heidelberg: Springer-Verlag. Raleigh, T. (2017). Another Argument Against Uniqueness. The Philosophical Quarterly, 67(267), 327-346. Raz, J. (1999). Engaging Reasons. Oxford: Oxford University Press. Roeber, B. (Forthcoming-a). Evidence, Judgment, and Belief at Will. Mind. Available at: https://doi.org/10.1093/mind/fzy065. Roeber, B. (Forthcoming-b). Permissive Situations and Direct Doxastic Control. Philosophy and Phenomenological Research. DOI: https://doi.org/10.1111/phpr.12594. Rosen, G. (2001). Nominalism, Naturalism, Epistemic Relativism. Philosophical Perspectives, 15, 69-91. Rubin, K. (2015). "Total Pragmatic Encroachment and Epistemic Permissiveness," in Pacific Philosophical Quarterly, 96, 12–38. Schoenfield, M. (2014) Permission to Believe: Why Permissivism is True and What It Tells Us About Irrelevant Influences on Belief. Noûs, 47(1), 193-218. Schoenfield, M. (forthcoming). Permissivism and the Value of Rationality: A Challenge to the Uniqueness Thesis. Philosophy and Phenomenological Research. DOI: https://doi.org/10.1111/phpr.12490. Schultheis, G. (2018). Living On The Edge: Against Epistemic Permissivism. Mind, 127(507), 863-879. Stanford, P. K. (2017). Underdetermination of Scientific Theory. In Edward N. Zalta (Ed.) The Stanford Encyclopedia of Philosophy (Winter 2017 Edition). Stapleford, S. (2018). Intraspecies Impermissivism. Episteme, 1-17. Steup, M. (2017). Believing Intentionally. Synthese, 194(8), 2673-2694. Sylvan, K. (2016). The Illusion of Discretion. Synthese, 193, 1635-1665. Thorstad, D. (forthcoming). Permissive Metaepistemology. Mind. DOI: https://doi.org/10.1093/mind/fzy044. Titelbaum, M. (2010). Not Enough There There: Evidence, Reasons, and Language Independence. Philosophical Perspectives, 24, 477–528. Titelbaum, M. & Kopec, M. (2019). When Rational Reasoners Reason Differently. In Magdalena BalcerakJackson and Brendan Balcerak-Jackson (eds.), Reasoning: Essays on Theoretical and Practical Thinking, pp. 205-231. New York: Oxford University Press. Turnbull, M.G. (2017). Underdetermination in Science: What It Is and Why We Should Care. Philosophy Compass, e12475. Weintraub, R. (2013). Can Steadfast Peer Disagreement Be Rational? Philosophical Quarterly, 63(253), 740-759. Weisberg, J. (Forthcoming). Could've Thought Otherwise. Philosopher's Imprint. Available at: https://jonathanweisberg.org/pdf/CTO.pdf. White, R. (2005). Epistemic Permissiveness. Philosophical Perspectives 19(1), 445-459. White, R. (2010). Evidential Symmetry and Mushy Credences. In Tamar Szabo Gendler and John Hawthorne (Eds.) Oxford Studies in Epistemology, (Vol. 3, pp. 161–186). OUP. 14 White, R. (2013). Evidence Cannot be Permissive. In Ernest Sosa and John Turri (Eds.), Contemporary Debates in Epistemology (2nd Edition, pp. 312-323). Hoboken, NJ: Wiley Blackwell.