The first theory is inspired by Wittgenstein’s final remarks, published as On Certainty (1969), detailing the epistemology of certainty in the context of Moore’s (1939) Proof of an External World, the problem of radical skepticism, and the structure of rational evaluation (cf. Pritchard 2011b, 2016a, b). Let’s begin with a statement of the view:
Wittgensteinian Theory:
Deep disagreements are disagreements over hinge commitments.Footnote 8
This kind of theory is strongly suggested by Fogelin (2005), Hazlett (2014), and Godden and Brenner (2010).Footnote 9 The main component of the theory is the technical term “hinge commitment”, of which there are many competing theories.Footnote 10 As a rough and ready characterization, however, hinge commitments are the background presuppositions of our world views and general areas of inquiry, such as physics, history, or geology. In particular, hinge commitments are given a certain epistemic role within our world views and inquiries, such as being:
“unearned certainties” or “standing certainties”—certainties one brings to any normal context. […] It is the idea of a ‘hinge’ proposition as a kind of ‘certainty of methodology’, as it were—a proposition a doubt about which would somehow commit one to doubting not just particular beliefs which we already hold but aspects of the way we habitually praise beliefs. (Wright 2004, p. 38).
The function that Wright highlights here is that doubting a hinge commitment should have the effect of doubting entire areas of inquiry. Compare this with Pritchard (2011b) on of the epistemic role of hinge commitments:
the suggestion is that the very possibility that one belief can count as a reason for or against another belief presupposes that there are some beliefs which play the role of being exempt from needing epistemic support. (Pritchard 2011b, p. 528).
What Pritchard stresses is the idea that hinge commitments stand outside our inquiries, as exempt from rational evaluation. Now that we have an initial idea of what hinge commitments are, we might wonder which propositions (or contents) are plausible candidates for being hinges. Here’s a recent list from Brueckner:
there is an external world, sense perception is reliable, I am not a brain in a vat, my faculty of reasoning is reliable, the Earth is more than three minutes old, testimony is reliable, memory is reliable. (Brueckner 2007, p. 285).
Notice that while most of the hinge commitments Brueckner lists are epistemic principles, not all of them are. For example, that there is an external world, that I’m not a brain in a vat, and that the Earth is more than three minutes old. One can imagine extending the list to fit with the other plausible candidates (see Coliva 2015). Wittgenstein himself names more:
that no one has ever been far from the Earth (§ 93).
—where everything he has seen or heard speaks for having, in his words, that conviction, and that nothing in his world picture speaks against it (see Wittgenstein 1969 § 93). Likewise:
that there is a brain inside his skull. (§ 118).
that the table is still there when no one sees it. (§ 120).
that the Earth is round. (§ 146).
Consider also:
I have a telephone conversation with New York. My friend tells me that his young trees have buds of such and such a kind. I am now convinced that his tree is.... Am I also convinced that the earth exists? (§ 208).
The existence of the earth is rather part of the whole picture which forms the starting-point of belief for me. (§ 209).
Wittgenstein’s basic idea seems to be that our epistemic practice of giving reasons for belief and doubt presupposes a background of certainties “exempt from doubt” (Wittgenstein 1969 §§ 341–343). The reason these certainties (however we understand this notion)Footnote 11 are exempt from doubt is that they make our space of reasons possible in the first place.
If the Wittgensteinian theory tells us that all deep disagreements are disagreements over hinge commitments, that raises the question of whether all disagreements over hinge commitments are deep disagreements.Footnote 12 For example, one might think that the disagreement over whether I have hands—a hinge commitment, according to Wittgenstein—is not quite a deep disagreement. At least, it doesn’t fit well with the paradigm cases of deep disagreement, such as the Young Earth Creationist case, among others.
However, I think that there is room to account for how some disagreements over whether I have hands, say, is a deep disagreement. First, we need to distinguish between what Thompson Clarke (1972) called plain doubts from unplain doubts, such as those cases when someone doubts the existence of their hands after an experiment or operation (cf. Clarke 1972, p. 758). In these cases, the doubts occur within their world views—these doubts make intuitive sense, given their picture of the world (cf. Stroud 1984, Chaps. 3–5). These are the plain doubts. The unplain doubts are the doubts about not just a proposition, or cluster of propositions, but an entire domain or worldview.Footnote 13 In such cases, the proposition I have hands is taken as representative of an entire domain, such as that there are mind-independent physical things, where disagreement about I have hands is representative of the wider domain.Footnote 14
We can make sense of such cases within the Wittgensteinian framework. To do this, we need to draw a distinction between direct and indirect deep disagreement. To unpack this distinction, consider a case in which two people disagree over whether some rock is older than 6000 years. This can go in at least two directions. It might be that the disputants are just disagreeing over the age of the rock as such, given certain background geological beliefs and aims. We can imagine one of them arguing that the rock is much older, due to its mineral composition, whereas the other disputant holds that it’s much younger, due to its location on the surface. In this kind of case, their disagreement is isolated: nothing much turns on it, just like in the peer disagreement cases, where it’s implausible that disagreement over the total restaurant bill, say, has wider implications for their beliefs about arithmetic sums, restaurants, and so on. However, it might also be that their disagreement over the age of that particular rock is a consequence of their deep disagreement over the age of the Earth. To put it more strongly, it might be that the point of their dispute over the age of that particular rock is to hone in on their deeper disagreement over the age of the Earth. In this way, the former is a proxy disagreement for the latter. These disagreements—where the disputants’ disagreement over one proposition which doesn’t look like a hinge commitment, but which is proxy for a disagreement over a hinge commitment—are indirect deep disagreements.
The basic idea here is that the proponent of the Wittgensteinian theory should draw a distinction between those disagreements which directly concern a hinge commitment, as in the Young Earth Creationist case, and those which indirectly concern a hinge commitment, as in our previous case over the age of some particular rock as proxy for a deep disagreement over young Earth creationism. We can sketch this distinction more generally as follows:
Direct deep disagreement:
S1 and S2 directly deeply disagree about whether H only if S1 and S2 disagree over H, and H is a hinge commitment.
Indirect deep disagreement:
S1 and S2 indirectly deeply disagree about whether P only if S1 and S2 disagree over P, and their disagreement over P commits them to disagreeing over a hinge commitment H.
This distinction also goes towards explaining the systematicity of deep disagreement. For example, if the Earth existed in the distant past such that it’s millions of years old or older is a hinge commitment, that commitment intuitively stands in certain logical, probabilistic, and epistemic relations to other propositions. For example, it entails that:
And it seems to make it less likely that:
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God created the Earth as early hominids would have found it, ex nihilio.
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There is a global conspiracy that is trying to deceive scientists into thinking that the Earth is much older than it really is, for their own nefarious ends.
Epistemically, it at least seems to speak in favor of propositions like:
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This particular mountain range that I see is much older than the young Earth creationist claims.
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The Himalayas have not been forming only over a short period, less than 6000 years.
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Fossils are not merely planted on the Earth by demons to deceive scientists and the public.
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The Earth has existed for much longer than any human beings have existed.
And it seems to be presupposed by certain domains of inquiry and certain methods, in the following ways:
Applied to indirect cases of deep disagreement, then, the Wittgensteinian theory will tell us that the young Earth creationist Henry and the new atheist Richard indirectly deeply disagree about whether P (about whether this particular rock is much older than 6000 years, say, millions of years older) only if they really do disagree over P, and their disagreement over P commits them—whether logically, probabilistically, or epistemically—to disagreeing over a hinge commitment H, say, that the Earth existed in the distant past (e.g., it existed millions of years ago, before any humans existed). In this case, the commitment is logical: Henry and Richard disagree over whether the rock is older than 6000 years old, and this logically commits them to disagreeing over whether the Earth existed in the distant past, so understood. However, it can also be epistemic. To see this, consider:
Young Earth Creationist*: Henry believes that radiocarbon dating is unreliable; that it’s just evil forces trying to deceive us. Richard believes that radiocarbon dating is reliable; that it’s a highly reliable method for getting true beliefs about the age of Earth’s geological formations.
The Wittgensteinian theory will say that Richard’s belief here epistemically presupposes the hinge commitment that the Earth is very old in the intended sense: presumably, he cannot consistently maintain that we ought to trust radiocarbon dating with regard to geological formations while denying that we shouldn’t do so in the numerous cases involving Earth’s geological formations. In turn, Henry is epistemically committed to rejecting that the Earth is very old, given his prior belief in the massive unreliability of radiocarbon dating (cf. Coliva 2015, p. 2).
How does the Wittgensteinian theory fare with respect to the desiderata for a satisfactory theory of deep disagreement? We’ve seen how it can account for the systematicity of deep disagreement. In what follows, I’ll explore how well it fares with respect to disagreement, reason-taking, and persistence. I will argue that the degree to which the Wittgensteinian theory can successfully account for the desiderata will turn on their theory of hinge commitments. First, take persistence. In the case where the deep disagreement is indirect, such as in the Young Earth Creationist* case, the explanation of persistence might be that the hinge commitments of their respective contrary beliefs lie in the background. Fogelin entertains this kind of explanation in the following passage:
They [deep disagreements] remain recalcitrant to adjudication because the sources of the disagreement—the framework propositions [the hinge commitments]—are allowed to lie in the background, working at a distance. (Fogelin 2005, p. 8 my additions).
This sort of explanation, however, only helps to explain the persistence of indirect deep disagreement, where the hinge commitments aren’t directly scrutinized. The thought is that such disagreements are persistent merely because what’s really at issue lies in the background, sheltered from critical attention. However, in the direct cases, this explanation won’t work as what’s really at issue gets critical attention from the disagreeing parties. Indeed, Fogelin himself goes on to reject this diagnosis of the persistence of deep disagreement. For Fogelin, the source of such persistence is not the fact that the hinge commitments lie in the background, but the fact that—even if brought to the foreground—they are part of a “whole system” of propositions (Fogelin 2005, p. 9). The burden on the Wittgensteinian would then be to explain why this fact renders disagreement over hinge commitments persistent, other than the contingent difficulty with assessing ‘whole systems’ of propositions.
At this juncture, the proponent of the Wittgensteinian theory might argue that pessimism about deep disagreement is true: that such disagreements are rationally irresolvable, that is, there is no epistemically rational response one ought to take, in light of their disagreement, which ought to yield agreement (cf. Feldman 2005 and; Lynch 2010, p. 269).Footnote 15 Recall the argument from Sect. 2 that a theory of deep disagreement should not presuppose that they are rationally irresolvable as part of the theory of what deep disagreement is. If the proponent of the Wittgensteinian theory seeks to explain persistence by reference to pessimism, then they ought to do so by way of an argument from the metaphysics and epistemology of deep disagreement, rather than as part of the analysis of what a deep disagreement is.
One potential challenge for the proponent of the Wittgensteinian theory here is that they might struggle to account for persistence without it thereby turning into an argument for pessimism. To see this, contrast two different accounts of the epistemology of hinge commitments:
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(i)
The non-epistemic theory, according to which hinge commitments are outside the scope of rational evaluation, and as such are neither justified nor unjustified (see Pritchard 2016a, b; Moyal-Sharrock 2016, 2004),Footnote 16 and:
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(ii)
The epistemic theory, according to which hinge commitments are within the scope of rational evaluation, and are potentially justified or unjustified, but in a non-paradigmatic way. In particular, our justification for hinge commitments consists in having a default entitlement to trust or accept them, in the absence of evidence or anything which indicates that they’re true. (Wright 2004, 2014; Hazlett 2014; Williams 1991)
I will bracket the reasons one might give for supporting these theories, since our focus is on the implications of these theories for deep disagreement. Prima facie, on the non-epistemic theory, there will be a direct argument for the conclusion that pessimism is true. After all, if hinge commitments are neither justifiable nor unjustifiable—that is, they are completely outside the space of epistemic reasons—then of course the exchange of reasons rationally ought to fail: for those reasons will neither justify the target hinge commitment nor its denial. On the non-epistemic theory, however, it’s a much harder question to settle. On the one hand, they won’t be able to exchange reasons in the ordinary sense, since they will lack evidence—or in general, anything which favors the truth of their hinge commitment—which rationally ought to get them to retain or change their attitude. On the other hand, the theory permits that there is some degree of rational support for hinge commitments by way of a default non-evidential entitlement to trust them. Provided that one can exchange this non-evidential rational support, then there will be a sense in which disputants can rationally resolve their deep disagreements, namely, by appealing to the hinge commitments that they are mutually entitled to trust. Of course, this would also go towards explaining persistence, as one might think that the explanation of the default entitlement for trusting hinge commitments is not something that will be easily accessible to the disagreeing parties; at least, in many real-world cases of deep disagreement. After all, intuitively the reason why, say, one has a default entitlement to trust that the Earth didn’t come into existence five minutes ago won’t be something that they can easily work out for themselves. Hence, while the proponent of the non-epistemic theory of hinge commitments will account for persistence by way of rational irresolvability, it is open to the proponent of the epistemic theory to account for persistence by reference to the cognitive opacity of their default entitlement to trust their hinge commitments and the fact that such commitments are non-evidential. In this fashion, the degree to which the proponent of the Wittgensteinian theory will struggle with the persistence desideratum will turn on their theory of hinge commitments generally.
This also relates to the reason-taking desideratum. This says that the theory needs to be consistent with the disagreeing parties taking themselves to be offering rational grounds for their attitude and grounds for their doubts about the other person’s attitude. But, of course, whether the theory can do this satisfactorily will depend on the theory of hinge commitments the proponent of the Wittgensteinian theory is working with. For example, if they are working with the non-epistemic theory, they’ll need to explain how the disagreeing parties are so easily misled into seeing themselves as giving reasons for their attitudes, when in fact there aren’t any to be given. An error theory of their self-perspective will need to be motivated and defended. A similar argument can be made for the epistemic theories. For in these cases, while one can give reasons for or against the hinge commitments, the reasons here are not paradigmatic—that is, they are not evidential or even truth-indicative. However, we typically find that the participants of deep disagreements take themselves to be presenting evidence for their own positive attitude and against their opponent’s attitude. (Consider, for example, how exchanges might go between young Earth creationists and new atheists). In this way, even the proponent of the Wittgensteinian account who accepts the epistemic theory of hinge commitments will struggle to not revise our initial thinking about deep disagreements. To be sure, this isn’t a knock-down argument against the Wittgensteinian account. Rather, it highlights how even if the Wittgensteinian accepts an epistemic account of hinge commitments, such as that the hinges are true propositions we have a non-evidential entitlement to trust, they’ll need to explain why the disputants so easily mistake themselves to be presenting evidence for their view and evidence against their opponent’s view.
Finally, satisfying the disagreement desideratum can be problematic for similar reasons, as it will turn on what their theory of hinge commitments is. For example, Wright (2014) takes the relevant attitude connected to hinge commitments to be trust: that one trusts that the hinge commitment is true.Footnote 17 Whether disagreement in propositional trust can constitute genuine disagreement, then, will be a question that needs to be answered. At the very least, it will need to be shown that disagreements in propositional trust retain the mechanics of disagreement in belief, since cases of deep disagreement seem to involve belief. Likewise, consider those theories such as non-propositionalism (Moyal-Sharrock 2004, 2016; Wright 1985), according to which hinge commitments are non-factual rules—that is, rules which are not truth-apt. Intuitively, since the objects of belief are propositions, it follows that not only can you not believe the hinge commitments, you cannot take any propositional attitude to them whatsoever. And, prima facie at least, that makes it hard to see how disagreement over them is possible.Footnote 18 Of course, this is not to say that the proponent of the Wittgensteinian theory cannot satisfy the disagreement desideratum. Rather, I am arguing that the extent to which they can turns on their theory of hinge commitments. And if one takes seriously the desiderata for an adequate theory of deep disagreement—and one accepts the Wittgensteinian theory of deep disagreement—this should constrain which account of hinge commitments one should accept.Footnote 19