## 1. The Nature of Moral Disagreement




There is little controversy about the existence of widespread
disagreement over moral issues, both within and between societies and
cultures. Often used examples are the debates about the morality of the
death penalty, of euthanasia, of abortion, and of meat-eating. Examples
of cultural differences include infanticide and geronticide and other
more or less alien practices that historians and anthropologists have
revealed. For example, Napoleon Chagnon's account of the ways of
the Yanomamo people in the Amazon basin is a popular source of
illustrations (Chagnon 1997, but see also Tierney 2003 for a critical
discussion). Some theorists assign special weight to disagreements
among philosophers and professional ethicists who have engaged in
systematic reflection about moral issues (e.g., Wong 1984, ch. 10 and
Leiter 2014). What they have in mind are, among other disputes, those
between utilitarians and Kantians about what makes an action morally
right and those between egalitarians and libertarians about what
justice requires. How deep the disagreement goes, however, and how it
is best explained, are disputed questions. So is another topic which in
a way precedes the others, namely, what it *is*, more
specifically, to disagree morally.


### 1.1 Conflicts of Belief or Clashes of Conative Attitudes?




People disagree morally when they have opposing moral convictions.
That much can be agreed by all theorists. What is debated is rather
what it means for such convictions to be opposing. For example, moral
realism entails cognitivism, and cognitivism is the view that moral
sentences--the sentences we typically use to express our moral
convictions--can be true and false and that the convictions
themselves constitute beliefs that purport to represent aspects of
reality. That element of their position allows realists to construe
moral disagreements as conflicts of belief along the lines of disputes
about (other) factual matters, i.e., as cases where persons give
inconsistent verdicts on one and the same truth-evaluable claim or
proposition. On that conception, if Jane thinks that meat-eating is
morally wrong while Eric denies so then they have incompatible beliefs
both of which cannot be true, just as when Jane believes while Eric
denies that the Earth is older than four thousand years.




To construe moral disagreements in that way is not, however, an
option for those non-cognitivists who deny that moral convictions are
beliefs and think that to judge that meat-eating is wrong is
instead to have a conative attitude towards meat-eating (such as an
attitude of dislike or a desire). Theorists of that kind rather
conceive of the opposition that a moral disagreement involves as a
clash of such attitudes (see, e.g., Stevenson 1944; and Blackburn 1984,
168). What the clash more specifically is supposed to consist in
depends on which version of non-cognitivism one is considering. If
moral convictions are taken to be desires, for example, then a moral
disagreement can be construed as a case where people have desires which
are not jointly satisfiable and thus motivate different courses
of
 action.[1]


### 1.2 Relativist Accounts




The fact that moral realists are cognitivists enables them to
construe moral disagreements as conflicts of belief, but some
cognitivists may also, just like non-cognitivists, need a conception
which is different from the realist one. Moral realism is associated
with the absolutist view that the truth conditions or contents of moral
sentences and moral convictions remain constant across speakers. For
example, the realist Richard Boyd insists that there is "a single
objective property which we're all talking about when we use the
term 'good' in moral contexts" (1988, 312). However,
there are also cognitivists who are relativists and think that the
truth conditions of moral sentences vary, depending for example on the
cultural or social groups which the speakers or believers belong to
(see, e.g., Harman 1978 and Wong 1984).




A crude version of relativism is the simple type of subjectivism
which holds that to state that an action is right or wrong is to report
something about one's own attitudes towards it. On such a view, if Jane states that meat-eating
is wrong while Eric claims that it is permitted, then Jane expresses
the belief that she disapproves of meat-eating while Eric expresses the
belief that he does not disapprove of it. Since both those beliefs can
be true, they are not incompatible. A common objection to subjectivism
is that it therefore, implausibly, represents paradigm cases of moral
disagreement as being merely apparent (Moore 1912, ch. 3), which
illustrates how facts that have to do with moral disagreement can help
a moral realist.




Similar objections can be raised against other forms of relativism,
although it may be easier for some of them to construe cases of moral
disagreement as conflicts of belief than for others. For example, on
one type of relativist view, what a speaker claims by stating that an
act is right is, roughly, that it is permitted by his or her moral
standards. So, if the speaker's claim is rejected by someone who
shares those standards, then they do after all have incompatible
beliefs (for this point, see Harman 1978; and Lopez de Sa 2015).
Disagreements between persons who do not share standards remain to be
accounted for, however.




In response to such objections, relativists can dissociate
themselves from the conception that a moral disagreement essentially
involves a conflict of belief and instead adopt the non-cognitivist
view which takes such disagreements to be clashes of conative
attitudes. They may do so, for example, by assuming that the moral
standards of a person consist in such attitudes (see, e.g., Wong 1984;
Dreier 1999; Bjornsson and Finlay 2010 and Marques 2014). That
would enable them to describe the situation with Jane and Eric as a
genuine moral dispute even if they concede that Jane's and
Eric's statements about the morality of meat-eating can both be
true. One might think that a relativist who chooses that path is left
with little reason to remain a cognitivist. But there are further forms
of relativism that allow for other options.




Some of those are explored in the debate regarding so-called
faultless disagreements (e.g., Kolbel 2003 and McFarlane 2014, ch.
6). On a view which is inspired by the more general position known as
"assessor relativism", the propositions that constitute the
contents of moral beliefs are the same independently of who the
believer is. But the truth-values of those contents nevertheless vary
depending on the standards of those who assess them (e.g., Kolbel
2004; and Schafer 2012). That view allows its advocates to remain
faithful to their relativist inclinations and still construe
Jane's and Eric's dispute as concerning one and the same
proposition which is affirmed by Jane and rejected by Eric. It also
allows them to claim that, for any spectator of the case, at most one
of Jane's and Eric's statements is true (since both cannot
be true relative to the same standards). This leaves them with a
conception of a moral disagreement which has at least some semblance to
the realist one. (For further discussion and criticism of the pertinent
account of disagreement, see Dreier 1999; and Francen 2010.)




The fact that different theorists thus ultimately employ different
ideas about what a moral disagreement amounts to may make one suspect
that they risk talking past each other when discussing further
questions, such as how much disagreement there is and how it is to be
explained. However, note that the disputes in question take place at a
quite theoretical level and are consistent with significant overlap
regarding what counts as a paradigm case of moral disagreement and
about the types of behavior such disagreements typically manifest
itself in. For example, both realists, non-cognitivists and others can
agree that moral disagreements are typically accompanied with clashes
of desires and that they are often causally rooted in conflicts of
non-moral belief (for example regarding the consequences of the
actions). That overlap helps to secure a shared subject matter for
discussions about (e.g.) how much disagreement there is.


### 1.3 Radical Moral Disagreements




All moral disagreements are not created equal from a metaethical
point of view, as some types are held to be more interesting than
others. This has partly to do with the fact that philosophers who
invoke moral disagreement in support of antirealist positions typically
want to avoid committing themselves to similar positions about other
areas where disagreement occurs, such as the empirical sciences.
Overgeneralization worries of that kind are addressed in section 6. But
a common response to them is to argue that there are crucial
differences between disagreement over moral issues and that which
occurs in the other areas.




On one such suggestion, many moral disagreements are particularly
pervasive and hard to resolve. The disagreements which arise for
example in the sciences can generally, it is held, be attributed to a
lack of evidence, bias, limited reasoning skills or similar cognitive
shortcomings and tend to go away when progress has been made in
removing those obstacles. That situation, however, is contrasted with
the one which is supposed to obtain in ethics, where many disagreements
allegedly would survive such measures and persist even if none of its
parties were affected by any factor which could plausibly be regarded
as an epistemic shortcoming. That is, the idea is that disagreements
would persist even in circumstances that are ideal in the sense that
they are the most favorable circumstances that human inquirers can hope
to achieve. This is why some theorists assign special weight to
disagreements among philosophers, who presumably are the most likely
candidates of being in such circumstances, given their training,
familiarity with each other's arguments, and the time they have
spent on reflecting on the issues.




In what follows, a moral disagreement that would persist in ideal
circumstances is called "radical". The claim that much of
the existing moral disagreement is radical is a premise in some
arguments from moral disagreement, although different arguments explain
its significance differently. It should be noted, however, that there
are also arguments which invoke weaker assumptions about the nature of
the existing disagreement and do not require that any of it is radical
(as is illustrated below).




Realists tend to agree with antirealists that radical moral
disagreements are the most troublesome (see, e.g., Parfit 2011, 546),
but they question the grounds for postulating such disagreements. They
might in that context use several complementary strategies. One, which
may be especially applicable to intercultural differences, is to argue
that some disagreements are in fact merely apparent. Thus, polygamy is
judged acceptable in some societies but deemed unacceptable in others.
If each of those judgments contains an implicit indexical element,
given which it holds only for the society in which it is held, then
they are not incompatible. Indeed, if the conditions that obtain in
those societies are different, then the situation is consistent with
assuming that certain more basic principles are accepted in all
societies, from which the differing views about polygamy could be
derived. (This possibility is noted by John Mackie, who however
downplays its importance, see 1977, 37.)




Another strategy is to insist that many moral disagreements can
after all be attributed to factors that are analogous to those that
underlie scientific ones (e.g., Smith 1994, 155-161) or to related
factors that are supposed to be especially pertinent to moral inquiry
(for a rich account of both options, see Brink 1989, ch. 7). For
example, it is often noted that moral disputes are frequently rooted in
disagreement about non-moral facts (e.g., Boyd 1988, 213), such as when
people have opposing views about the death penalty because of different
beliefs about the effects of permitting it. Those cases do arguably not
provide any particular problem for moral realism and can be seen as
instances of disagreement which is due to a lack of evidence. A further
distorting factor is self-interest, whose influence may make people
resist plausible moral views just because those views represent them or
the behavior they want to engage in as immoral. That mechanism may help
to explain why there is more disagreement in ethics than in areas where
self-interest is less of an issue (see Nagel 1986, 148; and
Shafer-Landau 2006, 219 for this suggestion). Yet further examples are
bias and prejudice, lack of imagination, and, as for example David
Brink has stressed (1989, 197-210), an insufficient amount of
systematic reflection. In specifically addressing the lack of
convergence among ethicists, Derek Parfit has made the congenial
suggestion that it is premature to draw antirealist conclusions from
it, as secular moral reasoning has been pursued for a relatively short
time (1984, 454). The suggestion is that fruitful moral inquiry has
been constrained by religious influences in ways that do not promote
truth-seeking, just as research about empirical issues was similarly
hampered before the scientific revolution. According to Parfit, this
means that it is not irrational to be hopeful about future convergence
of the very same kind that occurs in the sciences (see also Wedgewood
2014 for a discussion of disagreement among philosophers). The list of
available strategies could be extended, and the question, in the
context of the assessment of some (but not all) arguments from moral
disagreement, is what scope their application leaves for postulating
any remaining ones.


## 2. Empirical Research on Moral Disagreement




The question about the extent to which the existing moral
disagreement is radical is essentially an empirical one. Yet references
in the philosophical discussion to the numerous studies by
anthropologists, historians, psychologists and sociologists who have
documented the disagreement are relatively
 sparse.[2]
This may seem regrettable, and some have
accordingly emphasized that philosophers should pay more attention to
empirical research (see, e.g., Sturgeon 1994, 230 and Loeb 1998, 284).
That is surely good advice, but the absence of references to the
empirical literature is also to some extent understandable.




One reason for this is that much of the philosophical discussion
focuses on the implications of the claim that much moral disagreement
is radical, rather than on the truth of that claim. Another is that
some arguments merely appeal to the *possibility* of radical
moral disagreement and are consistent with thinking that all actual
disputes involve some shortcoming. (See e.g., Tolhurst 1987, and Wright
1992 and 1996. See also the references to antirealists who use thought
experiments of the type considered in section
 5.)[3]
That approach raises methodological questions of its
own, of course, especially if one is not willing to extend one's
antirealism to all other domains. For then one must explain how one can
establish that disagreements of the pertinent kind are possible in
ethics but not in the other domains. The role empirical evidence might
have in that context is a complex issue.




A further reason for the absence of references to empirical studies
in the metaethical literature is that their relevance is often unclear,
partly since the studies have typically not been guided by the rather
specific concerns that philosophers reflect on (such as whether the
disagreement is radical). However, that might be better seen as a
reason to scrutinize those studies more carefully than to ignore them
altogether. It may also be a reason for philosophers to take a more
active role in the empirical research themselves and to find ways to
collaborate with those who are trained in those areas.




Some important efforts along those lines have in fact been made. A
prominent example is Richard Brandt's study (1954) of the Hopi
people, which revealed differences in basic moral attitudes between the
Hopi and white Americans that could not, he thought, be explained with
differences in non-moral beliefs. (See Moody-Adams 1997 for a critique,
and Abarbanell and Hauser 2010 and Barrett et al. 2016 for two more
recent examples.) An attempt to argue that there is empirical evidence
for the existence of radical moral disagreement that has been widely
discussed in recent years has been made by John Doris, Alexandra
Plakias and Stephen Stich (Doris and Plakias 2008a; Doris and Plakias
2008b, and Doris and Stich 2007). They appeal to research conducted by
the social psychologists Dov Cohen and Richard Nisbett (1996) about why
certain types of violence among non-Hispanic whites are more common in
the American South than in the North. Cohen and Nisbett attribute this
difference to the existence in the South of a "culture of
honor", which permits harsh responses even to minor insults. As
for why such a culture is more prevalent there, Cohen and Nisbett point
to the fact that early European migrants to the United States settled
in different regions. Many who went to the South were descendants of
people whose morals had been forged in herding economies (in Scotland,
for example), where a reputation for being prone to violent retaliation
lessened the risk of having one's cattle stolen.




Doris et al. argue that the difference Cohen and Nisbett have
revealed is a plausible candidate of a disagreement which would persist
under ideal conditions, as it is unreasonable to attribute it to
unawareness of non-moral facts or to other obvious types of distorting
factors. But they also acknowledge the tentativeness of their
contention and that there are further options for those who want to
explain away the difference (see, e.g., Doris et al. 2020). One is to
pursue the aforementioned suggestion by Brink (see also Loeb 1998) to
the effect that the failure to expose one's moral beliefs to
theoretical reflection is a shortcoming. The type of reflection he has
in mind is associated with a reflective equilibrium-style method for
moral inquiry, which prescribes the pursuit of coherence and
systematicity. Arguably, the evidence presented by Cohen and Nisbett is
not enough to confidently conclude that the disagreements would survive
competent applications of that method. (See Fitzpatrick 2014. For
further discussion, see Tersman 2006, ch. 2; Bloomfield 2008; and
Fraser and Hauser 2010.)




The idea that an insufficient amount of reflection counts as a
shortcoming may justify focusing especially on disagreements among
philosophers, as Brian Leiter (2014) does. But a problem is that the
available characterizations of the pertinent method of reflection are
rather vague. It may therefore be hard to determine whether
*any* individual has applied it competently or not. Moreover,
how any such method is to be specified, and even if it is to be used at
all, are controversial issues within philosophy. Something similar
holds for other potential candidates of relevant shortcomings. For
example, what about cases where our moral convictions are influenced by
our emotions? It is common to view such influence as a distorting
factor (e.g., Singer 2005 and Sayre-McCord 2015), but on some views in
moral epistemology, and given the benign roles emotions sometimes play
in cognitive processes, it may need to be qualified (see Le Doux 1996
and Nussbaum 2001 for two influential accounts of the epistemic
significance of emotions). Before those and many related issues are
settled, and thus before we have established a comprehensive list of
clearly defined factors which count as shortcomings, all confident
estimates of the extent to which the existing moral disagreement is
radical may seem premature.


## 3. Metaphysical Arguments from Moral Disagreement


### 3.1 The Argument from Relativity




Much of the contemporary metaethical discussion about moral
disagreement is inspired by John Mackie's "argument from
relativity", which is offered in support of his nihilist
metaphysical claim that there are no moral facts. Mackie's
argument is often interpreted as an inference to the best explanation.
On that interpretation, the existence of widespread moral disagreement
supports the thesis that there are no moral facts because it is implied
by the best explanation of the disagreement. However, although that
construal of Mackie's argument is quite common (e.g., Brink 1989,
197; McGrath 2008, 90; Joyce 2010, 46 (but see also Joyce 2018); Vavova
2014, 304; and Clarke-Doane 2020, 148), it is also questionable.




Mackie's brief presentation of his argument begins as
follows:



> 
> 
> The argument from relativity has as its premiss the well-known
> variation in moral codes from one society to another and from one
> period to another, and also the differences in moral beliefs between
> different groups and classes within a complex community (1977,
> 36).




He acknowledges that there is no direct step from the diversity to
the conclusion that there are no moral facts and stresses that the
disputes which occur in the sciences do not support analogous
conclusions about them. To justify this mixed verdict, he stresses
that, while "scientific disagreement results from speculative
inferences or explanatory hypotheses based on inadequate
evidence" (1977, 36), moral disagreement should be explained in a
different way:



> 
> 
> [T]he argument from relativity has some force simply because the
> actual variations in the moral codes are more readily explained by the
> hypothesis that they reflect ways of life than by the hypothesis that
> they express perceptions, most of them seriously inadequate and badly
> distorted, of objective values. (1977, 37)




What makes it questionable to construe Mackie's argument as an
inference to the best explanation is that his way-of-life explanation
seems completely neutral as to the existence of moral facts. The
account is illustrated by the claim that "people approve of
monogamy because they participate in a monogamous life" rather
than the other way round, and that view is surely consistent both with
the existence and the non-existence of moral facts. It is accordingly
hard to see how the alleged superiority of Mackie's way of
life-explanation of moral diversity confirms the idea that it is best
explained by assuming that moral facts do not exist.




When exploring the possibility of an alternative reconstruction, it
is helpful to distinguish between two claims:


1. The best explanation of the variation in moral codes
entails that there are no moral facts.
2. The best explanation of the variation in moral codes does not
entail that there are moral facts.




Given the neutrality of Mackie's way of life-account relative
to the existence of moral facts, the supposition that it offers a
superior explanation of the variation does not imply (i). However, it
does imply the weaker claim (ii), which is what Mackie notes by
contrasting the way of life-account with "the hypothesis that
[our moral convictions] express perceptions, most of them seriously
inadequate and badly distorted, of objective values". Can (ii) be
used in a compelling objection to moral realism? One option is to try
for an indirect one which targets the grounds for being a realist,
rather than realism itself. (ii) does not entail that the variation is
a direct reason to reject realism, but it does indicate that realism
fails to obtain support from it. That is obviously an unsurprising
result, but if the way-of-life hypothesis is incorporated in a broader
theory, which provides the best explanation also of other aspects of
moral discourse, then it may deprive realists of more important sources
of support. For example, some moral realists (e.g., Sturgeon 1988, 229,
Smith 1994, 188, and Huemer 2016) stress that although there is plenty
of moral disagreement, there is also some amount of convergence. Issues
that previously were intensely debated are currently less controversial
(Smith mentions slavery, for example). The inspiration of these
realists may be the arguments for scientific realism which invoke the
(arguably more impressive) convergence that occurs there (see Devitt
1984 for a discussion). However, if a theory which incorporates the
way-of-life hypothesis and at the same time remains non-committal about
moral facts were to provide a better explanation not only of the
divergence but also of the convergence among moral judgments, then
arguments for moral realism of that kind would fail. If the broader
theory were in addition to explain why we form moral convictions in the
first place, then it would provide significant support for the core
claim of Gilbert Harman's much discussed argument against moral
realism, according to which we should not posit moral facts, as they
are not needed in the best explanation of anything observable. (See
Harman 1977 and Sturgeon 1988 for a realist response.)


### 3.2 Disagreement and Inaccessibility




Of course, the role such a reconstruction of Mackie's argument
assigns to moral disagreement is exceedingly limited, so it hardly
accounts for the attention that moral disagreement has received in the
debate about moral realism. Can the argument be reconstructed in a more
direct way? As several commentators have pointed out, what might be
needed is an epistemic premise (e.g., Bennigson 1996; Loeb 1998;
Tersman 2006, ch. 3, Enoch 2009; and Locke 2017). The question is what
the existence of moral facts predicts about existing moral
disagreement, and the problem is that it is hard to see how it
generates any such predictions on its own. Further assumptions are
needed, and one candidate is the idea that the facts, if they exist,
are accessible to us in the sense that we can in favorable epistemic
circumstances acquire knowledge of them. David Wiggins has formulated
the idea as follows: "If X is true, then X will under favourable
circumstances command convergence" (1987, 147). Given such a
claim, one could then argue that moral realism predicts less
disagreement (in the relevant circumstances) than that which actually
exists. This would be a direct reason to reject it.




This alternative construal of the argument leaves realists with the
option of denying that the moral facts they posit are accessible.
However, that is a move realists are typically not inclined to make. A
persuasive argument to the effect that moral realists are committed to
viewing moral facts as inaccessible would rather be seen as an
embarrassment, as it would leave them, to use Russ
Shafer-Landau's phrase, with "a logically coherent position
that contains about zero appeal". (2012, 1). Indeed, some
realists even make the claim that moral facts are epistemically
accessible a part of their definition of the position (Boyd 1988, 182).
A more common response is therefore to try to find ways to reconcile
the existing disagreement both with the existence and with the
accessibility of moral facts.




The prospects of such a response depend on what the accessibility is
taken to entail. There may be little reason for realists to go beyond
the relatively modest claim that we can attain knowledge of some moral
facts in favorable circumstances. Given such a weak interpretation of
"accessible", realists may employ all the strategies
outlined in section 1.3 to argue that most of the existing disagreement
occurs between persons who are not in ideal circumstances which would
render it irrelevant in the present context. After all, the fact that
people have failed to reach agreement (which entails, on a realist
view, that some have failed to obtain knowledge) in conditions that are
*not* favorable need not show that they would fail also in
circumstances that *are*. As for the remaining disagreement,
such as that between philosophers, realists could point out that it
primarily concerns highly general and theoretical facts whose
accessibility they can consistently remain agnostic about, for example
due to underdetermination concerns.




In addition, realists may in fact concede that some contested moral
issues do not allow for objectively correct answers and thus grant some
amount of indeterminacy in the moral realm. The idea is that they may
do so and still insist that other moral questions have such answers, by
attributing the indeterminacy to vagueness which in turn may be the
result of the applicability of incommensurable values or requirements
(see, e.g., Brink 1989, 202; Sturgeon 1994, 95; and Shafer-Landau 1994
and 1995). That proposal has received some attention (e.g.,
Constantinescu 2012 and 2014) and deserves further examination.
However, a potential concern with it is that the set of moral issues
which may most plausibly be taken to involve vagueness might not
overlap so well with the set of issues over which there is the fiercest
disagreement among competent inquirers (for this point, see Loeb 1998,
290; Tersman 2006, 133; and Schroeter and Schroeter 2013, 7-8).
Wouldn't such inquirers be likely to spot the indeterminacy and
abstain from forming any (conflicting) beliefs about those issues? If
so, then the appeal to vagueness provides just limited help to realists
in accommodating the most likely candidates for qualifying as radical
moral disagreements.


## 4. Epistemological Arguments from Moral Disagreement




The argument to the effect that moral disagreement generates
problems for moral realists by committing them to the inaccessibility
of moral facts is ultimately of an epistemological nature. It is thus
congenial with the more general idea that disagreement sometimes raises
skeptical worries by suggesting that our grounds for the contested
beliefs are inadequate and that they thus fail to be adequately
justified or amount to knowledge. And although that idea applies to
other areas as well, it is often taken to have a special relevance to
ethics, given the extent of the disagreement that occurs there.




The skeptical conclusions that moral disagreement has been taken to
warrant vary in strength, both modally and in terms of scope. The claim
that moral facts are inaccessible is modally strong in that it goes
beyond saying just that we actually lack moral knowledge or justified
moral beliefs. But moral disagreement has been invoked in defense of
modally weaker claims as well. Note that the fact that a form of
skepticism is weak in the modal sense and just pertains to our actual
situation does not mean that it cannot be a part of an argument against
moral realism. At least, that is so as long as it is sufficiently broad
in scope. For example, if it were shown that we are in fact unjustified
in thinking of *any* moral claim that it is a truth, then that
would arguably diminish our justification for thinking that there are
such truths in the first place (see further Tersman 2019). However, if
a skeptical conclusion is weak not only in the modal sense but also in
the scope sense, so that it applies only to a limited subset of our
moral beliefs, then it is less likely to have a role to play in a
forceful challenge against moral realism (or other positions that seek
to leave room for moral
 knowledge).[4]
Still, the contention that moral disagreement has
such implications is interesting in its own right.




The focus below is on arguments which seek to cast doubt on the
existence of moral knowledge, even granted that there are moral truths.
An alternative approach is to first argue that the disagreement
directly excludes the existence of moral truths and then to simply
derive the thesis that there is no moral knowledge from that conclusion
(given that knowledge presupposes truth). That alternative strategy
will be set aside in this section. Thus, since the arguments are
supposed to support skeptical conclusions independently of any
rejection of moral truths, they need to establish that our moral
beliefs violate some other precondition of knowledge, such as, most
commonly, justification.




Any argument to that effect raises general questions about what it
takes for a belief to constitute knowledge or to be justified.
Nevertheless, those who put forward skeptical arguments from moral
disagreement do not always invoke any such general view. The reason
might be that they believe that the skeptical conclusions follow on
just about any of the most promising theories that have emerged in
epistemology, which obviously would make the arguments less vulnerable
(see e.g., Tolhurst 1987 for this suggestion). However, others do
explicitly state some general view of knowledge or justification on
which they rely.


### 4.1 Moral Peer Disagreement




One example of an argument which invokes a specific view is developed
by Sarah McGrath (2008). The view in question entails that your belief
about some topic does not amount to knowledge if it is "denied by
another person of whom it is true that: you have no more reason to
think that he or she is in error than you are". Armed with this
principle, McGrath offers an argument to the effect that many of our
moral beliefs do not constitute knowledge. What she in particular has
in mind are those beliefs that concern issues "that tend to be
hotly contested in the applied ethics literature as well as in the
broader culture" (92-93), such as the ones about the death
penalty and meat-eating. (Derek Parfit considers a challenge which he
articulates similarly. See 2011, 546.)




McGrath's principle is congenial with the position known as
"conciliationism" in the peer disagreement debate, although
that position is more often stated in terms of justified or rational
belief than knowledge (see Frances 2019 for an overview of the
positions and arguments the debate revolves around). An interlocutor is
your peer, roughly, if he or she is just as well equipped as you are
(for example, in terms of evidence and reasoning skills) when it comes
to figuring out the truth about topics of the kind the contested belief
concerns. According to conciliationism, if one learns that one's
beliefs are opposed by a peer, then one should drop the beliefs or at
least reduce one's confidence in them. Conciliationism thus
offers a way to argue that moral disagreement sometimes has the type of
significance assigned to it by moral skeptics (see Rowland 2020 for an
extensive discussion of the strategy).




Conciliationism has been met with criticism from theorists who
instead favor "steadfastness" in the face of peer
disagreement. And the fact that conciliationism is thus a contested
doctrine also raises the self-defeat worry that it can be turned
against itself as it may then seem to call for its own abandonment. But
an advantage of conciliationism in the present context is that it
allows moral skeptics to derive skeptical conclusions from moral
disagreement without having to assume that the parties are in ideal
circumstances. After all, two persons could be in equally favorable
epistemic situations even if their situations could be improved. At the
same time, however, the conclusions a skeptic may, *via*
conciliationism, hope to derive from such disagreements are
correspondingly modest. They seem at best to entail that the parties
currently lack justified beliefs or knowledge and do not rule out that
knowledge is in principle attainable. As Richard Feldman puts it, the
skepticism we get from conciliationism is "a kind of contingent
real-world skepticism" which does not address, for example,
"whether it is possible for us to know about the existence and
nature of things in the external world" (2006, 217).




The type of skepticism which follows from conciliationism is likely
to be limited in the scope sense as well. The reason is that, besides
the disputes about the death penalty, abortion, and so on, there are
also issues over which disagreement is rare, such as, to use a couple
of examples which are often mentioned in this context (e.g., in Vavova
2014), whether pain is bad and whether parents have a responsibility to
take care of their children. A global moral skeptic might try to
counter that point by noting that those claims are also opposed by some
people, namely error theorists such as Mackie, who reject all
(positive) moral claims as being incorrect in one fell sweep. But even
if that group includes some very capable thinkers, they are vastly
outnumbered by others, including philosophers who appear no less
competent. As McGrath suggests, the fact that the error theorists thus
are outliers might in itself be seen as a reason for not regarding them
as peers, in spite of their philosophical capabilities (2008, 95). (For
a different argument to the effect that conciliationism yields at most
a very restricted form of skepticism, see Vavova 2014.)


### 4.2 Disagreement and Safety




Is there a plausible way to accommodate the fact that there is
near-universal agreement about some moral claims while still
maintaining that moral disagreement supports global moral skepticism?
One option is to argue that the disagreement can play a more indirect
role (see, e.g., Enoch 2009). The idea could be that it is not the
disagreement itself which makes our moral beliefs unjustified, but
rather some underlying factor which the disagreement is a symptom of
(and which might obtain also when the symptom is absent). One may
imagine, for example, that even if just some moral claims attract
disagreement, the best explanation of the diversity of moral views is
nevertheless a theory about the causal background of moral beliefs
which holds generally. If that theory in turn suggests that the beliefs
are caused in a way that undermines their justification, it allows us
to see how the disagreement can support global moral skepticism, even
granted that some moral claims do not generate controversy. In this
type of argument, the relevance of the disagreement is somewhat reduced
(though not entirely obliterated) compared to that assigned to it by
conciliationism, as disagreement merely plays the role of being
evidence that the more fundamental skepticism-generating condition
obtains.




According to one suggestion along those lines, what moral
disagreements reveal is that the abilities or methods we use to form
our moral beliefs are not sufficiently reliable or truth-tracking. They
may fail to be so, for example, by being such that, even if the beliefs
we have formed by using those methods are in fact true, we could easily
have ended up with false ones. If we could not easily have been
mistaken (by using the same methods that we used to form our actual
beliefs), then our beliefs are sometimes said to be "safe".
Some theorists take safety to be a necessary condition of knowledge
(see, e.g., Pritchard 2005 and Williamson 2000). If it could be shown
that existing moral disagreements indicate that our moral beliefs are
not safe, then this offers a way forward for moral skeptics (for this
idea, see e.g., Mogensen 2016; Hirvela 2017; Risberg and Tersman 2019;
and Clarke-Doane 2020, 148).




How is moral disagreement supposed to show that our moral beliefs
are unsafe? Consider a person *a* whose beliefs about a set of
contested moral topics are true. The beliefs are safe only if
*a*, by using the same methods, could not easily have formed
beliefs that contradict her actual ones in circumstances where the
moral facts remain the same. Now, what disagreement about
*a*'s beliefs entails is that some people have *in
fact* formed beliefs that contradict *a*'s actual ones
in circumstances where (we are supposing) the moral facts remain the
same. So, if (some of) those persons have used the same methods as
*a* and if the existence of those persons accordingly indicates
that *a* could easily have formed those beliefs as well by using
those methods (on the ground, perhaps, that they have grown up in
similar social or cultural circumstances and have been exposed to
similar types of education), then it also indicates that
*a*'s beliefs are unsafe.




This is just a sketch of an argument, of course, and it faces
serious challenges. One is to clarify the notion of a
"method", which is required in order to make sense of the
claim that different people use the same methods to arrive at
incompatible moral beliefs. Another problem is to explain in more
precise terms what it means to say that it could "easily"
have happened that someone had formed an opposing belief. It is a
tricky task to provide precise definitions of those notions which both
render the view that safety is required for knowledge plausible and
vindicate the role assigned to disagreement by the indicated
argument.


### 4.3 Merely Possible Disagreement




An alternative way to try to accommodate the fact that there is
near-universal agreement about some moral claims, while still pursuing
a global form of moral skepticism, is to argue that the mere
possibility of certain types of disagreement is enough to secure
skeptical conclusions. That approach has been tried by William Tolhurst
(1987, but see also Schiffer 2002, 288).




Tolhurst presents an argument whose conclusion is that no moral
beliefs are ever justified, if those beliefs are understood "on
the realist model" (610). Its premises include two epistemic
principles which together imply that if a person's belief that P
is justified, then it is not possible for there to be another person
who is similar in all epistemically relevant respects and who believes
not-P. A further premise is that, for every person *a* and every
moral claim M which is accepted by *a*, it *is* indeed
possible for there to be another person who shares *a*'s
non-moral beliefs, is equally good at reasoning and is (therefore)
similar in all relevant respects, and yet believes the negation of M.
Given that further premise, it follows that no moral belief is
justified. As indicated, Tolhurst takes this argument to be conditional
on a realist understanding of moral beliefs. However, the premises make
no mention of that assumption, and Tolhurst does not elaborate on how
it would help a non-skeptic to adopt an alternative
 account.[5]




Is the argument compelling? Tolhurst suggests that the best option
for those who want to resist it is to postulate "the existence of
a special ability to ascertain [...] moral truth" (614, see
Wright 1992, 152-156, for a related suggestion). For that would allow
one to hold that there are relevant respects in which we may differ
from our possible opponents, besides those concerning our non-moral
beliefs and (general) reasoning skills. In the ensuing discussion,
Tolhurst notes that, by postulating a special ability, realists would
"incur a significant theoretical debt" (621), but he holds
open whether they can make good on it.




Tolhurst thus ultimately reaches the verdict that his argument is
inconclusive, and there are additional ways to question it besides that
which invokes the idea of a special cognitive ability. For example, his
two principles can be challenged with reference to the
"permissivist" view that the same set of evidence can
license different doxastic attitudes toward a proposition (see, e.g.,
White 2005 about permissivism). However, Tolhurst also makes some
remarks about how to move forward which are of general interest. The
upshot of those remarks is that the argument he developed should be
assessed from a holistic perspective. The legitimacy of invoking a
specifically moral cognitive ability depends, he thinks, on
"whether a realist theory which includes [that] hypothesis can,
as a whole, explain moral [and non-moral] phenomena more effectively
than its antirealist rivals" (621). This is an important
observation in view of that arguments from moral disagreement are often
assessed under the assumption that they are expected to establish their
skeptical or antirealist conclusions all by themselves and are
dismissed if it is found that they fail to do so. What the holistic
approach suggests, however, is that, even if they fail in that sense,
it is still conceivable that they might contribute to a successful
*combined* challenge, by joining forces with other skeptical or
antirealist arguments, such as the evolutionary debunking ones. (The
evolutionary debunking strategy is described and discussed in
FitzPatrick 2021. For an attempt to combine it with arguments from
disagreement, see Tersman 2017, but see also Klenk 2018 for a
critique.)


## 5. Moral Disagreement and the Semantics (and Metasemantics) of Moral Language




The previous sections address potential epistemological and
metaphysical implications of moral disagreement. However, it is also
thought to be relevant to the fields of moral semantics and moral
metasemantics (which focus on questions about the meanings and
functions of moral sentences and about the nature and contents of moral
convictions). Moral disagreements manifest themselves in disputes over
sentences that involve terms such as "good" and
"right" and in differences regarding when and on what basis
those terms are to be applied. Since such patterns of language use
belong to the phenomena semantical and metasemantical theories seek to
account for, the disagreement has been taken to have relevance also in
those areas.




Much of that discussion focuses on a certain challenge against moral
realism, according to which it generates implausible implications about
when people are in a genuine moral disagreement. Realism is supposed to
have those implications because of its commitment to cognitivism and
absolutism, and the challenge is accordingly offered of in support of
non-cognitivist or relativist views. However, the implications do not
follow from cognitivism or absolutism alone, but only given certain
metasemantical assumptions about how the truth conditions of moral
sentences and the contents of moral beliefs are determined. So, an
important question is if there are plausible assumptions of that kind
with which realists can combine their theory to avoid the
implications.


### 5.1 Disagreement and Charity




An early contribution to the debate was made by Richard Hare (1952,
esp. 146-149, but see also Stevenson 1963, and Blackburn 1984 and 1993,
ch. 11). He imagined a scenario with two facts which he assumed could
co-exist. The first is the fact that different sets of speakers
systematically apply "good" to different persons and
actions and on the basis of different criteria of application with
little overlap. The second is the fact that they all use "good"
as, in Hare's phrase, a "general adjective of
commendation". According to Hare, the first fact implies that
there is no single property which "good" is used to refer
to by all speakers in the scenario. That is, supposing that the term is
used to refer at all, the fact suggests that it refers to different
properties for different speakers. This in turn means that their
disputes about how to apply "good" need not reflect any
conflicts of belief, as the belief that an item has one property is
compatible with its lacking some other property (provided that the
properties are appropriately distinct). Hare's point, however,
was that, in virtue of the second fact, it would still be plausible to
interpret those speakers as being in in a genuine moral dispute when
arguing about whether to apply "good" or not. Hare took
this conclusion to suggest that moral disagreements are best seen as
clashes of commands rather than as conflicts of belief and provided the
argument in support of his non-cognitivist view that the
("primary") function of moral terms and sentences is to
express such commands.




A common realist response to the argument is to question whether the
differences in language use which are assumed in Hare's scenario
really do rule out co-reference. Whether it does is a metasemantical
question. On a metasemantical view which potentially vindicates
Hare's contention, we interpret the referential terms of a
speaker correctly only if we assign referents "charitably".
An assignment is charitable in the relevant sense if, given the
assignment, most or many of the speaker's ascriptions of the
terms come out true (e.g., Davidson 1973; and Lewis 1983). On that
view, it does indeed seem hard to reconcile co-reference with a lack of
convergence or agreement regarding how a term of the pertinent kind is
to be applied. However, the charity-based approach is challenged by
other metasemantical positions, including those which take the
reference of at least some terms to be determined in ways that allow
for more error. By invoking such a position, a realist could
potentially deny Hare's conclusion that the speakers in his
scenario use "good" to refer (if at all) to different
properties.


### 5.2 New Wave Moral Realism




That strategy has been pursued by Richard Boyd in defense of his
naturalist form of moral realism, which is sometimes referred to as
"new wave moral realism" (Boyd 1988, but see also Brink
1989). Boyd appeals to a causal theory of reference. His version of
that approach is complex and differs in significant ways from more
familiar versions (such as those offered in Putnam 1972 and Kripke
1980). But the main idea is that moral terms refer to the properties
that "causally regulate" our uses of those terms, including
our dispositions to apply them in particular cases. Such regulation
presupposes that there are mechanisms which causally connect
(instantiations of) the properties with the uses. Boyd insists that
those mechanisms must ensure *some* tendency to apply the term
reliably to actions, persons or states of affairs which have the
properties in question, to secure a degree of epistemic access to them.
However, he also stresses that this constraint does not preclude
serious errors. Our use of "good" can be relevantly
regulated by a certain property even if we are ignorant of it and even
if our ignorance results in many affirmations which are false (given
that the term refers to the property in question). Differences in our
use of moral terms and sentences of the kind that Hare highlighted are
therefore consistent with co-reference and accordingly also with
thinking that there is a shared (factual) subject matter over which the
people in his scenario express conflicting beliefs by using the
pertinent terms and sentences.




However, although mere differences in application do not undermine
co-reference on Boyd's account, other factors do. That is the
point of departure of a criticism which Terrence Horgan and Mark
Timmons have developed in a series of influential papers (first set out
in Horgan and Timmons 1991 and 1992), in which they argue that
Boyd's causal approach also commits realists to implications of
the type Hare pointed to.




The argument is illustrated by the "Moral Twin Earth"
thought experiment. Moral Twin Earth is a planet whose inhabitants
speak a language which is similar to ours in that it includes the moral
terms "good", "right", "wrong" and
so on. Moreover, the social and psychological roles those terms play in
their communities overlap with those they play in our communities. We
may imagine, for example, that they figure in similar ways in their
deliberations and discussions about how to act, and that the
inhabitants are, like us, in general motivated to act and avoid acting
in ways they classify as "right" and "wrong",
respectively. A further stipulation--a crucial one in this
context--is that the inhabitants' uses of the pertinent
terms are causally regulated by different properties than those that
regulate our uses of them. Thus, their use of "right" is
regulated by the property actions have by satisfying certain
deontological requirements, while ours is regulated by the
consequentialist property actions have when maximizing happiness. Given
that stipulation, "right" does not, on Boyd's
account, refer to the same property for us and for them. So, again, the
disputes we might have with them about how to apply "right"
need not reflect any conflicts of belief. What Horgan and Timmons
suggest, however, in a way which mirrors Hare's argumentation, is
that it would still be plausible to construe our disputes with them
regarding how to apply it as genuine moral disagreements, in virtue of
the overlap in social and psychological roles (for a different critique
of Boyd's approach, see Schroeter and Schroeter 2013).


### 5.3 Further Developments and Responses




The Moral Twin Earth thought experiment has led philosophers to
explore other metasemantical options, besides Boyd's causal
theory, which realists may use to argue that they can accommodate the
pertinent intuitions about when people are in a genuine moral
disagreement. These options include conceptual role semantics (Wedgwood
2001) and David Lewis' views on "reference magnetism"
(van Roojen 2006; Dunaway and McPherson 2016; Williams 2016; see Eklund
2017 for further discussion). The general problem that those
alternative suggestions are intended to solve can be indicated as
follows. Horgan's and Timmons' argument suggests that the
fact that a speaker's use of "right" is regulated by
a certain property is of limited relevance to the plausibility of
viewing us as being in a genuine disagreement when discussing its
application. What matters are instead the considerations pertaining to
the social and psychological roles the term plays in the
speaker's community and in his or her deliberations. To
accommodate the intuitions the moral twin earth thought experiment
evokes (and to handle new scenarios that antirealists might come up
with), what realists seem to need is thus an account to the effect that
those very considerations are enough to secure co-reference. That is,
the account must entail that the features that tempt us to interpret
the speaker as being in a genuine moral disagreement with us are the
same as, or at least reliably correlated with, the features on which
co-reference is taken to supervene.




The difficulties of developing an account which fits that bill are
elevated by the fact that there are further requirements it arguably
must meet. One such additional requirement is that the account must be
plausibly applicable also to other domains besides morality (see
Schroeter and Schroeter 2013 and Dunaway and McPherson 2016 for
discussions of the relevant constraints). To design an account of
reference which entails that there is co-reference in exactly the cases
where we intuitively think that people disagree in scenarios such as
the Moral Twin Earth one may not be such a difficult task. But the idea
behind the additional requirement is that this would be *ad hoc*
if the account were only applicable to moral terms (or to normative
terms in general). Note in this context that Boyd takes his account to
apply not only to moral terms but to natural kind terms quite generally
(which is the type he thinks that "good" and
"right" are instances of), including "water"
and "gold". If one were to drop that "generality
constraint", allowing for a metasemantic view that applies just
to moral or other normative terms, then the task for the realist would
be simpler.




Is there a way to justify such a move? In this connection, one might
wonder if it would help the moral realist to be a non-naturalist about
the nature of moral properties, i.e., to hold that they are not
reducible to natural properties and (on some characterizations of the
theory) to assume that they are *sui generis* and causally
inert. That is an issue which has not been in the foreground in the
debate following the Horgan's and Timmons' contributions,
as they specifically target Boyd's (and Brink's) naturalist
form of realism.




Whether non-naturalism really is less vulnerable to the challenge is
not clear, however. On the one hand, the assumption that moral
properties are *sui generis* may help realists to defend the
exceptionalist view that the reference of moral terms is determined in
a special way (at least along with terms in other domains that deal
with non-natural properties). On the other hand, explaining how our
moral terms have come to refer to such properties may be extra
difficult, especially given the further assumption that they are
causally inert (the issue is discussed in Suikkanen 2017). It should
also be noted that the soundness of at least the charity-based versions
of the challenge seems unaffected by what view one takes on the nature
of moral properties. On those versions, systematic differences
regarding the application of moral terms threaten to undermine
co-reference regardless of whether the candidate properties to which
those terms refer are taken to be non-natural or not.




The responses that so far have been discussed are aimed to show that
realists are not in fact committed to the allegedly implausible
implications (viz., that certain moral disputes are merely apparent) to
which antirealists seek to tie them. Another type of response is to
bite the bullet, to insist that the pertinent implications are after
all acceptable, and to explain away their counter-intuitiveness in a
way which is consistent with realism.




On one such suggestion, the parties of some disputes about how to
apply "right" or "good" do indeed use the terms
to refer to different properties. But what they really disagree about
is which property the terms *should* be used to refer to, in
some non-moral sense of "should" (see, e.g., Merli 2002 and
Plunkett and Sundell 2013). Presumably, however, this suggestion helps
the realist only if that other, background dispute can in turn be
construed as a conflict of belief. So, if the challenge could be
extended to cover the "should" which is relevant in that
context as well, which it seems hard to rule out, nothing much is
accomplished (see Tersman 2006, 100 and Dunaway and McPherson 2016,
661, for this point).




A different option is to concede that the appearance in the relevant
cases of a genuine dispute is best explained in terms of clashes of
conative attitudes, and to stress that this explanation is not
incompatible with realism. After all, realists can consistently agree
that moral convictions are usually accompanied with such attitudes (see
Jackson and Pettit 1998 for this point). By making that response,
realists in effect give up trying to account for the cases by using
assumptions that form a part of their theory. For even if the
assumption that the cases involve clashing attitudes is not
inconsistent with realism it is also not entailed by it. A potential
problem with that type of response is raised by the natural view that
the justification of a theory about moral semantics (such as the form
of cognitivism which forms a component of realism) depends at least in
part on its ability to explain how people behave or relate to disputes
about how to apply moral terms. The relevant facts include the
willingness of such disputants to see themselves as standing in genuine
opposition to each other. Thus, if, in some cases, that fact is best
explained by assumptions that are external to that theory, then some
bits of the relevant evidence fail to support it. That is a potential
disadvantage of the pertinent response, although there may obviously be
other sets of evidence which make up for the (alleged) loss (see
further Tersman 2006, ch. 5 and Bjornsson 2012).


## 6. Over-Generalization and Self-Defeat Worries




Widespread disagreement occurs not only in ethics but in just about
any domain, including the sciences. A longstanding worry about
skeptical or antirealist arguments from moral disagreement has
therefore been that they generate analogous conclusions about those
other domains as well (e.g., Brink 1989 and Huemer 2005). More
recently, the debate has come to focus not only on the empirical
sciences but also on areas such as mathematics (Clarke-Doane 2020) and
other philosophical areas besides ethics, including epistemology,
metaphysics and metaethics itself (e.g., Shafer-Landau 2006; Cuneo
2007).




According to the idea which underlies the concern, the skeptical or
antirealist arguments from disagreement that apply to ethics and the
versions that apply to the other domains are equally compelling. The
suggestion that this kind of parity obtains is in turn offered as an
objection to the arguments, as it is supposed to show that they
"over-generalize" and lead to "too much"
skepticism or antirealism. Why too much? That is, why cannot those who
favor the arguments just embrace their alleged wider implications as
yet being, though perhaps surprising and unintended, perfectly
acceptable? Two answers to that question can be discerned. (The
distinction between the answers is noted in Tersman 2010 and in
Poltzler 2020.)




On the first answer, the parity undermines the skeptical or
antirealist arguments because there are independent reasons for
rejecting the conclusions they yield when applied to the other areas
(it is assumed here that those reasons do not in turn undermine the
parity claim). This would arguably cast doubts on the arguments. For if
they yield incorrect conclusions in those contexts, why think that they
do a better job in the case of ethics? In other words, the idea is that
the parity provides resources for a *reductio* *ad
absurdum* of sorts of the arguments.




Which are the independent reasons that may back up such a challenge?
One option is to appeal to the sheer counter-intuitiveness of the wider
implications. Thus, Shafer-Landau writes:



> 
> 
> If intractable disagreement [...] is enough to warrant an
> antirealist diagnosis of an area, then the whole of philosophy must be
> demoted. That simply is implausible: there really is (or isn't)
> such a thing as probabilistic causation, numbers without
> spatio-temporal location, actions that are both free and determined,
> etc. (2006, 220).




Others raise more specific objections of this kind. For example,
Frank Jackson (1999) targets arguments for moral non-cognitivism and
claims that they, when appropriately adjusted, provide equal support
for non-cognitivism about theoretical rationality (i.e., judgments
about when beliefs are rational). The latter view is in turn criticized
on the ground that it commits one, *via* certain (contestable)
assumptions about the nature of beliefs, to think "that there are
no believers and no beliefs" (423). The absurdity of that
implication is taken by Jackson to refute non-cognitivism about
theoretical rationality. But he also takes it to undermine the
arguments that are used in its support, and therefore also the versions
of those arguments which apply to ethics (even if no similarly absurd
implication can be directly derived from moral non-cognitivism).




How can advocates of arguments from moral disagreement respond to
such challenges? The prospects depend partly on which other domain(s)
ethics is compared with. A connection of the pertinent sort with some
domains may result in less pressing problems than a connection with
others. For example, the jury is arguably still out regarding
antirealism about mathematics, as such positions do have able defenders
(e.g., Field 1989). So, if an overgeneralization challenge depends on
the implausibility of those positions, there is some room for advocates
of the arguments to resist the objection.




The second answer to why the alleged parity between ethics and other
domains undermines arguments from disagreement may generate a more
decisive objection, however. On that answer, the parity makes the
arguments self-defeating and the position of their advocates
incoherent.




That type of challenge can in turn take different forms. A
straightforward way to argue that an argument is self-defeating is to
show that its advocates are committed to claims that are outright
inconsistent with it (i.e., either with its conclusion or with its
premises). Consider for example an argument which is aimed at
establishing the error-theoretical thesis that all moral claims are
false. If that argument can be extended to metaethics, so that it
commits its advocates to thinking that all metaethical claims are false
as well (including the error theory), then they have obviously ended up
in an awkward place.




Another type of self-defeat or incoherence is epistemic, as
contrasted with the "strict" type just indicated. An
argument is epistemically self-defeating, we may say, if we by
affirming it commit ourselves to thinking that at least one of its
elements is unjustified (rather than false). That is the type of
incoherence that Derek Parfit has tried to saddle moral
non-cognitivists with by stressing (like Jackson) that they are
committed to non-cognitivism about theoretical rationality as well.
Parfit takes the latter view to imply that "to call a thing
rational is not to state a matter of fact" (2011, 409). And the
problem for the moral non-cognitivist which he discerns is that
"[i]f there could not be truths about what it is rational to
believe [...] it could not be rational to believe anything",
including moral non-cognitivism.




Parfit makes a problematic move by deriving the normative claim that
it is not rational to believe in non-cognitivism from a metanormative
thesis about what it is to state such a claim. But it is easy enough to
come up with other examples of epistemic self-defeat. Thus, consider an
argument aimed at establishing global moral skepticism. Any such
argument must invoke some epistemological principle *via* which
the skeptical conclusion can be derived. So, if the argument applies
just as well (*mutatis mutandis*) to epistemology and shows that
we lack justified beliefs in that area as well, then it commits its
advocates to thinking that one of its premises is not justified. This
type of incoherence is presumably less worrying than the first one, as
it neither rules out the validity of the argument nor the truth of its
premises. But it is clearly sufficiently worrying to raise concerns
about the target argument's dialectical significance (see Sampson
2019 for discussion).




The above discussion illustrates that an argument's
vulnerability to an overgeneralization challenge depends on which other
domain(s) the challenge focuses on, as well as on the conclusion of the
argument (whether it pursues a local or global form of moral
skepticism, for example). However, it also depends on *how* the
argument reaches its conclusion and on which further premises it
involves besides the one that postulates disagreement.




The last point is important. The most straightforward way to respond
to an overgeneralization objection is to insist that there are after
all crucial differences between the disagreement that occurs in ethics
and that which occur in the other areas. This is what Mackie did by
suggesting that scientific disagreements, unlike moral ones, result
from speculative inferences or inadequate evidence. Whether the
disagreements are different in such ways is an empirical issue which is
hard to resolve. However, the fact that any argument from moral
disagreement involves further premises besides that which posits
disagreement leaves their advocates with other options when trying to
challenge the relevant parity claim. That is, it potentially allows
them to concede that there is "just as much" or "just
as deep" disagreement in ethics and the other areas and still
consistently argue that the disagreement that occurs in those areas
license different conclusions about their status.




Take for example the semantical arguments which were considered in
the previous section. They rely on the idea that it is
counter-intuitive to construe certain disputes over the application of
moral terms as being merely apparent. In analogous disputes in
epistemology, such as those between internalists and externalists about
when to classify beliefs as "justified", such a diagnosis
may be more acceptable. At least, that is the upshot of a suggestion by
William Alston, who indicates that it helps explain the lack of
convergence in epistemology (see Alston 2005a, esp. ch. 1; Alston
2005b, 137; and Tersman 2010).




Additional options are generated by the above-mentioned idea that
although appeals to moral disagreement are not capable of establishing
any skeptical or antirealist conclusions on their own, they may do so
when combined with other strategies, such as the evolutionary debunking
ones. Such a combined strategy might be more promising in the moral
case than, say, in the epistemological case. A crucial assumption in
evolutionary debunking arguments is that an evolutionary explanation of
our moral convictions does not support their reliability (although it
may be consistent with it). Whether that is so in the case of our
epistemic convictions is a separate issue and may call for a different
answer, which potentially leaves room for a different assessment of a
combined argument which is applied in that context (see further Tersman
2010).




The availability of these ways to respond to overgeneralization
objections adds to the difficulties of reaching a conclusive assessment
of them and thus also to the difficulty of assessing the arguments that
provide their target themselves. It thereby confirms a more general
observation, namely, that while each of the skeptical or antirealist
arguments surveyed above involves problematic elements, quick and
impatient dismissals of appeals to moral disagreement are often
similarly dubious. That may be frustrating but is also unsurprising.
The discussion about the metaethical significance of moral disagreement
raises intricate and philosophically central issues about knowledge,
justification, how reference is determined, and so on. This helps to
explain why progress is slower than one might desire but also why the
phenomenon commands continued attention from philosophers.