## 1. Why Externalism?



Given the tension with SK, why should we accept EXT in the first
place? One reason is that EXT is more or less entailed by many
contemporary theories of content. For instance, several theories say
(in short) that a
 concept[5]
 has its content in virtue of certain causal relations the concept
bears to an environmental referent (Dretske 1981, Millikan 1984; 1989,
Fodor 1987; 1990; also, cf. Kripke 1972 and Evans 1982, ch. 6). Others
see mental content as posited when interpreting a subject
vis-a-vis objects in her environment (Davidson 1973; 1987,
Dennett 1975). Still others see content as determined by the
inferences that feature the relevant concept. Such an inference,
moreover, is often defined partly by the environmental object which
normally prompts the inference, or in which the inference normally
terminates (Sellars 1954).



Predictably, such theories face various difficulties--so none
provide a decisive case for EXT. Yet the foremost arguments for the
view are not so parochial. These arguments instead rest on various
thought experiments, purporting to show that internally identical
subjects can host different thought contents, solely because of
environmental differences (Putnam 1973; 1975, McGinn 1977, Stich 1978,
Burge 1979; 1982; 1986). If the thought experiments are right about
this, then internal states do not wholly determine thought content.
The environment would play a part as well.



The most famous experiment imagines a remote planet called "Twin
Earth," a planet which is superficially indiscernible from Earth
(so that even its events parallel the events on Earth). But there is
one key difference: The compound H2O occurs nowhere on Twin
Earth. In its place is a different compound that looks, tastes, etc.,
exactly the same, which we may call "XYZ". Now consider
Oscar, a normal adult English speaker, along with his Twin Earth
doppelganger, Twin Oscar. (Ignore that people are mostly
H2O; that's an accident of this example.) The
externalist intuition is that, even if these "twins" are
unschooled in chemistry, Oscar uses 'water' to refer to
H2O yet Twin Oscar uses 'water' to refer to
XYZ. After all, when Oscar asserts "water is scrumptious,"
this is directed at water, yet Twin Oscar's parallel assertion
is in reference to XYZ, a.k.a. twin
 water.[6]



Moreover, suppose we accept the Fregean view that the meaning of a
term determines what the term refers to (or in Carnap's words,
that "intension determines
 extension").[7]
 Then, given the different referents, the twins' terms must have
different *meanings* as well. But Oscar and Twin Oscar are
physical duplicates; so it appears the meaning of 'water'
is not wholly fixed by speakers' internal states. Rather, the
environment also figures into
 it.[8]



This claim about linguistic meaning is then extended to the content of
mental representations for *natural kinds* like water, and for
*non-natural kinds* like sofas (where the latter are defined by
social convention) (McGinn 1977, Stich 1978, Burge 1979; 1982; 1986).
Consider that when Oscar says "sofas are delightful," he
expresses a *thought* that references sofas. But suppose that
Twin Oscar's community defines a "sofa" slightly
differently, so that broad, overstuffed armchairs count as
"sofas." Consequently, when Twin Oscar asserts
"sofas are delightful," he differs from Oscar in
expressing a thought that refers to (among other things) broad,
overstuffed armchairs. But again, if content determines reference, the
difference in reference demonstrates a difference in intension or
content, in spite of identical internal
 states.[9]
 Thus we arrive at EXT.



Some might find these science fiction stories extravagant, and it may
be unclear whether they teach us anything about the real world. Yet
there are actual examples which also illustrate the point (Ludlow
1995b; see also Butler 1997, Tye
 1998).[10]
 Consider that 'chicory' and 'endive' have
their denotations switched between Standard American English and
British English. The two types of salad green also seem identical to
the untrained eye (or palate, as the case may be). Thus a Brit and an
American, both untrained, might be internally the same in all relevant
respects, yet refer to different greens when asserting "chicory
is scrumptious." So 'chicory' will express a concept
with different content, despite the subjects being internally alike.
(Notably, 'water' itself might vary in content among
different locations in the actual world. What flows from taps contains
different admixtures in different municipalities. Cf. Malt 1994.)



Nevertheless, some philosophers reject these considerations for a
variety of reasons (Zemach 1976, Mellor 1977, Searle 1983, ch. 8, Bach
1988; 1998, Crane 1991, Rosenberg 1994, Chomsky 1995; 2000, Segal
2000, Martinich & Stroll 2007, ch. 5, Farkas 2008, Pollock 2015;
see also Fine 1975). Other philosophers do not reject EXT as much as
*restrict* it: They posit a kind of content--so called
"narrow" content--which is determined independently
of the environment (Block 1986, Loar 1988, Georgalis 1994; 1999,
Chalmers 1996; 2002, Jackson 1998, Siewart 1998, Horgan & Tienson
2002, Wikforss 2007, Mendola 2008; see also the entry on
 narrow content).
 As one illustration, two-dimensionalists characterize narrow content
as a function that takes an environment as input and outputs the
"wide" content of the concept in that environment, i.e.,
the content of which EXT is true (Chalmers 1996; 2002). And
putatively, the problem with armchair self-knowledge does not arise
with narrow content. (For more, see Fernandez 2004 as well as the
entry on
 two-dimensional semantics.)



The debate on whether EXT is unrestrictedly true is important, but
this is not the place to discuss it. (Yet see the entry on
 externalism about mental content.)
 For our purposes, the main point is that EXT is not without support,
and so there is some reason to hold onto the view despite the apparent
tension with SK.


## 2. The Reductio to Armchair Knowledge of the External World



But is the tension real? One pro argument is a reductio ad absurdum:
The claim is that EXT and SK jointly entail an obvious falsehood,
namely, that Oscar can know from the armchair contingent facts about
the external world (McKinsey 1991; 1994; 2002; 2007, Brown 1995,
Boghossian 1997; 1998). If so, then EXT and SK cannot be jointly true,
and the incompatibilist wins the debate.



The argument is this: Assume EXT and SK for reductio, and
let'*E*' name the *E*nvironmental condition
that EXT requires for a concept to have a water content (versus a twin
 content).[11]
 Apparently, then, EXT and SK imply that Oscar can know from the
armchair--or in the incompatibilist's idiom, know
"apriori"--both of the following:


1. If Oscar is thinking that water is wet, then *E*
obtains.
2. Oscar is thinking that water is wet.



In this, *p* is known apriori (or just: "*p* is
apriori") iff *p* is known without a concerted empirical
investigation of the external world. (Note that introspective
knowledge counts as "apriori" in this context, even though
it arises from a kind of introspective experience. For more on the
present conception of the apriori, see Miller 1997, Davies 1998,
Nuccetelli 1999, and McLaughlin 2000; 2003). On the current line, (1)
can be known apriori if EXT is true (though as we shall see, there are
different ways to spin this). Whereas, (2) is apriori given SK. Yet if
Oscar has apriori knowledge of both (1) and (2), Oscar can then use
modus ponens to know apriori that:


3. *E* obtains.



But *E* is an environmental condition that presumably can only be
known empirically. So EXT and SK apparently lead to an absurd sort of
apriori knowledge, and are thus incompatible. (Henceforth, call this
argument "the reductio.")



Before we consider the compatibilist's replies, one
clarification of the reductio is in order. For it may be unclear
whether EXT entails (1) in the first place (whether apriori or not).
However, if EXT is derived from one of the causal theories of content
(from section
 1),
 then acquiring the water concept requires causally interacting with
water (if only via your linguistic community). (See McGinn 1989, ch. 1
passim, McCullough 1999, but contrast with McLaughlin & Tye 1998a,
Ball 2007.) Thus possessing the concept requires the existence of
water, meaning that the view entails (1). Even so, if the
incompatibilist wants to add that (1) is entailed *apriori*,
she would need the contentious premise that some causal theory of
content is entirely apriori.



So on a more charitable reading, the incompatibilist's reductio
does not target an externalism based on a causal theory. It is rather
directed at a view based solely on the Twin Earth thought experiments,
given that the experiments are more naturally seen as apriori. (But
see Baker 2007.) For the remainder of section 2,
'externalism' and 'EXT' shall refer
exclusively to this kind of Twin Earth based externalism.


### 2.1 Reply 1: Environmental Implications are Empirical



Yet it may remain unclear whether EXT is committed to (1). For the
thought experiments alone do not assume that water is
*necessary* for water thoughts (Brueckner 1992). The thought
experiments indeed assume that suitable interaction with water is
*sufficient* for Oscar to have water thoughts. They also assume
that Twin Oscar's interactions with XYZ are insufficient. But
this does not yet imply that interacting with water is the
*only* way that someone can arrive at water thoughts.



However, this assumes that *E* is a condition where water exists
(or existed at one time). Yet the incompatibilist's reductio
need not assume that (McKinsey 1994; 2002; 2007). One can first see
the incompatibilist as presenting a dilemma, corresponding to two ways
that EXT might be interpreted. On the first reading, EXT holds that a
water thought *logically* or *conceptually* implies some
environmental condition *E*. Yet for the incompatibilist, logical
or conceptual implications are apriori. So if EXT on this first
reading is true, (1) is apriori (and nothing here prejudges what
*E*
 is).[12]



Even so, the first reading is not the usual interpretation of EXT. On
a more standard construal, EXT holds that a water thought
*metaphysically* implies some environmental condition *E*.
Yet metaphysical implications, e.g., that"water is wet"
implies "H2O is wet," are not always apriori.
(See Kripke 1972 and the entry on
 Rigid Designators).
 So the apriority of (1) is not guaranteed here, and the reductio
seems in doubt.



Yet incompatibilists reply that the second reading cannot be what is
really intended. For it renders EXT into something
*trivial*--it is obvious that Oscar's water thoughts
metaphysically imply a number of external conditions, e.g., that Oscar
was born (McKinsey, 1994; 2002; 2007, Rowlands 2003). But EXT is
supposed to be more substantive than that. Compatibilists reply,
however, that the thought experiments suggest that a water thought
metaphysically implies some *content specific* environmental
condition, such as the existence of *water* (Brueckner
1995).



So the way seems clear for the compatibilist to reject the apriority
of (1). But as before, the incompatibilist may respond that we are
illicitly assuming *E* to be the condition simply that water
exists. Yet the strongest version of the reductio may not assume that.
One might instead understand *E* as follows:


4. *E* = Water or a community using the water concept exists
(or, existed) (Brown 1995, Boghossian 1997).



If *E* is identified as this disjunctive condition, it is more
believable that (1) is apriori under EXT. And if that is believed, the
reductio then presses that EXT permits apriori knowledge that
*either* water *or* a community exists. Yet that too
should not be apriori.



But assuming (4), why would EXT render (1) apriori? Granted, many
externalists find it apriori plausible that besides interacting with
water, Oscar could acquire the water concept from other community
members. That suggests that if Oscar has acquired the concept, (4)
must be true. However, some externalists conjecture that there are
other conditions under which the water concept can be acquired. Even
if Oscar is socially isolated and lives in a waterless environment, he
can conceivably arrive at the concept by hypothesizing the
H2O molecule (Burge 1982). If this cannot be ruled out
apriori, then EXT does not secure the apriority of (1)--even if
(4) is assumed.



Yet incompatibilists reply that (ironically) *these very
reflections* reveal apriori something that should not be apriori
(Brown 1995, Boghossian 1997). Namely: *If* Oscar is aware that
he has no such hypotheses (i.e., if he is "agnostic" about
chemical essences), then (1) must be knowable apriori. In more detail,
if Oscar is agnostic about chemistry and knows that apriori about
himself, he can use the reflections above to know apriori that his
water thoughts metaphysically require the existence of water or a
community. From there, apriori knowledge of *E* seems
imminent.



Nevertheless, the compatibilist's opening objection lingers:
Nothing yet shows that the *only* ways to acquire water
thoughts, under EXT, are in the ways catalogued so far (Ball 2007).
For all that has been shown, it remains possible that essence-agnostic
Oscar is socially isolated and his water thoughts reference no natural
kind. (See also Gallois & Hawthorne 1996, Gallois 2008, and
McLaughlin & Tye 1998a, b, c.)



But perhaps additional apriori considerations can rule this out (Brown
1995). Suppose that Oscar has the concept of a sofa and knowledgeably
applies the concept in a variety of cases. Yet assume he is agnostic
on whether the concept applies to broad overstuffed armchairs. Then,
if Oscar has no community to settle the matter, EXT may suggest that
Oscar's concept is *indeterminate* in what it refers to.
And that seems odd.



However, the compatibilist may ask why this is supposed to be a
problem (McLaughlin & Tye, 1998a, b, c). The indeterminacy may
show only that Oscar's concept is *vague* and not that
Oscar fails to possess any concept whatsoever. (Brown 2001 replies by
defining 'agnostic' so it applies only if the concept is
non-vague. Yet Brown 2004, ch. 8 concedes that Oscar then can no
longer know apriori if he is "agnostic.") So, here too, it
seems that EXT does not reveal apriori that water thoughts
metaphysically require a content specific environmental condition.


### 2.2 Reply 2: Externalism about Empty Concepts



Still, it may remain intuitively compelling that a Twin Earth thought
experiment, if cogent, would show (1) apriori--even if *E*
is just the condition where water
 exists.[13]
 For the experiments seem to show apriori that, to have the bona fide
*water* concept, the concept must be non-empty, i.e., its
referent must exist. However, a compatibilist can counter this by
offering a semantics of empty concepts that is consonant with EXT
(Stoneham 1999, Sawyer 2003, Goldberg 2006b, Haukioja 2006, Parent
2017, ch. 4; see also Pryor 2007, pp. 184-185). Even so, there
are two arguments in the literature suggesting that any externalist
view of empty concepts must fail (Boghossian 1997; 1998, Segal 2000,
Besson 2012).



On its face, empty-concept externalism can be supported by a Twin
Earth thought experiment (Boghossian
 1997).[14]
 Consider "Dry Earth"--a planet exactly like ours,
except wherever water occurs on Earth, there are only watery looking
holograms (though Dry Earthians mistake these for a real kind). The
intuition is that unlike Oscar, Dry Oscar uses 'water' to
express an empty concept. And if Dry Oscar is not referring to water,
then as before, the Frege-Carnap view implies that his concept has a
different intension or content. So even for empty concepts, content
seems determined partly by facts about the environment (including
facts about what is *absent* from the environment).



However, carrying this further may lead to absurdity, since
externalism about empty concepts can suggest that a concept's
*form* is sensitive to the environment (Boghossian 1997; 1998).
Suppose, as is plausible, that empty concepts have a
*descriptive* form--so that (e.g.) the unicorn concept is
understood as the concept "horse with a horn." For most
externalists, this contrasts with our concept of water which does not
have a descriptive form, but is rather atomic. If that is correct,
then Dry Oscar expresses a descriptive concept when using
'water', whereas Oscar expresses an atomic one. In which
case, the environmental difference creates a difference in
*form* as well as content. But that is strange, since form
seems to be a purely syntactic matter, fixed entirely by what's
in the head.



At least one compatibilist has tried embracing environment-dependent
syntax, though he concedes it is an uncomfortable view (Ludlow 2003;
2011). At the least, such a stance would seem ad hoc (Besson 2012).
Others question the "supervenience principle" in the
argument, viz., that a difference in form necessitates a difference in
internal state (Corbi 1998, Brown 1999, Korman 2006, Parent
2015a, 2017, ch. 4). Further argument has been offered for this
principle (Boghossian 1998), yet such arguments may beg the question
by presupposing a Chomskian, internalist notion of logical form
(Parent 2015a, 2017, ch. 4).



However this issue unfolds, externalism about empty concepts faces a
further challenge (Segal 2000, pp. 54-56). Consider: Either the
externalist sees the unicorn-concept as necessarily empty or
 not.[15]
 If the former, then the view implies that unicorns are impossible
objects, like round squares. And that is rather counterintuitive (yet
see Kripke 1972 on unicorns). But taking the other horn (sorry), a
contingently empty concept would have its content fixed by descriptors
like "horse with a horn." In this case, EXT seems false.
For the constancy of the descriptors guarantees that the concept has
the same content in every possible world, whether or not it contains
unicorns (Segal 2000; see also Besson 2012). (But for replies, see
Korman 2006 and Parent 2015a, 2017, ch. 4.)


### 2.3 Reply 3: Transmission Failure



If externalism about empty concepts fails, then EXT may well entail
(1) apriori, per the incompatibilist's reductio. But a
compatibilist could try a different line of resistance. She might
simply grant that (1) and (2) are apriori, but still try to block
apriori knowledge of (3). (Here too, *E* is assumed to be just
the condition where water exists, though it is believed that similar
points hold if (4) is true instead.) The most prominent strategy of
this type is to deny the "transmission of warrant" that
supposedly occurs in the deduction of (3) from (1) and (2) (hereafter,
"the deduction"). The idea is that, even if the
externalist agrees that (1) and (2) are warranted, none of this
warrant "transmits" to (3) in the deduction (Davies 1998;
2000; 2003a; 2003b, Wright 2000a; 2000b; 2003; 2011; 2102; 2015; see
also Wright 1985). If so, the deduction cannot furnish apriori
knowledge of (3), pace the incompatibilist.



For brevity, let us call the advocate of transmission failure
"the advocate." Then, the advocate's core idea is
that even though (1) and (2) entail (3), they do not *prove*
(3). For in brief, the "proof" seems question begging (cf.
McLaughlin 2000). 'Question begging', however, may not be
the right word here (Beebee 2001, Prichard 2002, Silins 2011). Still,
the idea is that (3) in some sense is presupposed, once the deduction
gets started. If such circularity is operative, then the deduction
cannot create any warrant for (3), much less prove it. Or in the
advocate's idiom, the warrant for (1) and (2) cannot
*transmit* to (3) in virtue of the deduction.



As a satisficing
 approximation,[16]
 the transmission of warrant generally occurs iff:



> 
> 
> 
> |  |  |
> | --- | --- |
> | (TW) | If a subject *S* is warranted in believing *p* and is
> warranted in believing that *p* entails *q* (and *S*
> further recognizes that *q* follows deductively from these
> beliefs)--then *S* acquires, potentially for the first time,
> a warrant in believing *q*. (Cf. Wright 2000a, p.
> 140-141.) |
> 
> 
> 



Yet (TW) should be distinguished from epistemic closure, as discussed
by some anti-skeptics (e.g., Dretske 1970). Some compatibilists think
that the reductio also exemplifies a failure of epistemic closure (see
Bernecker 2000, Hale 2000, Sawyer 2006, although see Sawyer 2015 for a
"contrastive" account that upholds closure). Regardless,
transmission failure is a different affair, if only because epistemic
closure concerns "knowledge" rather than
"warrant." Nevertheless, warrant transmission differs even
from the "closure of warrant," characterized as
follows:



> 
> 
> 
> |  |  |
> | --- | --- |
> | (CW) | If *S* is warranted in believing *p* and warranted in
> believing that *p* entails *q*, then *S* is warranted
> in believing *q* (or is able to be thus warranted). |
> 
> 
> 



The difference between transmission and warrant closure is best seen
in cases of question begging. Take an overtly circular argument which
concludes (3) using (3) as a premise. Trivially, anyone warranted in
believing the premise is warranted in believing the conclusion. So
(CW) is satisfied in this case. But the argument does not
*transmit* warrant to its conclusion; it cannot bestow any
warrant on (3) that was not already there. From a different angle, a
person cannot use the argument to gain knowledge of (3) *for the
very first time*. Hence, warrant fails to transmit onto the
conclusion, even though warrant closure holds
 trivially.[17]




The advocate thus cries "transmission failure" in relation
to (1)-(3), on the grounds that (3) is
"presupposed." Yet in this case, the presupposition charge
is not as straightforward. For clarity's sake, let us call (1)
and (2) the "\*premises" of the deduction, to contrast them
with the premises of the reductio. (The latter are stronger in
claiming that the former are apriori.) Then, the advocate bases the
presupposition charge on the following: An externalist can rationally
grant that the \*premises are warranted only if she has certain
"background assumptions" which *already* imply (3).
The point is sometimes framed in terms of "information
dependence:" An externalist who grants warrant to the \*premises
"rationally requires certain collateral information" that
includes (3) (Wright 2000a, p. 149). Consequently, an
externalist's "acceptance of those [background]
assumptions cannot be rationally combined with doubt about the truth
of [(3)]" (Davies 2003a, p. 43, but contrast Davies 2000, p.
402).



For simplicity (since rational externalists are the only ones we care
about), assume henceforth that "the externalist" is
rational. Then, the presupposition charge is most readily appreciated
via the following
 approximation:[18]
 When considering the reductio,



> 
> 
> 
> |  |  |
> | --- | --- |
> | B(3) | An externalist grants that the \*premises are warranted only if
> (3) is already among her *B*ackground assumptions. |
> 
> 
> 



Note: B(3) is a "second order" thesis about the
dialectics of the reductio; the antecedent is a condition where the
externalist *grants* that the \*premises are warranted
(regardless of whether they *are* warranted). Thus
B(3) says that the externalist will be presuming (3), if
she concedes warrant to the \*premises in the first place. It is in
this sense that (3) is presupposed once the deduction is mobilized,
resulting in transmission failure.



An argument for B(3) has yet to be given, but there are two
on offer. The first opens with the remark that, since EXT requires
water for thinking "water is wet" (as all parties are
currently allowing), the same is true of the self-attributing thought
"I'm thinking that water is wet." (Davies 2000
2003a, 2003b). However, if a person regards this metaphysical claim as
*warranted* along with (2) --then she cannot rationally
put (3) in doubt. For if the existence of water were in doubt, then
given her warranted metaphysical claim, this rationally compels a
further doubt on whether the *thought* expressed by (2) exists
in the first place. But the existence of the thought must be
acknowledged before one can concede a warrant to it. So our
externalist will rationally allow a warrant to both \*premises only if
she already assumes (3) as background, which is just what
B(3)says.



The second argument we might attribute to a character called
"Wrightgenstein" or just "W." for short, since
it originates in Crispin Wright's interpretive work on
Wittgenstein. Qua externalist, W. acknowledges the possibility of
error in discerning one's own mental contents, as when Dry Oscar
misjudges his empty concept to have a natural kind content. Even so,
he sees no reason to surrender the warrant possessed by ordinary
judgments about content. This parallels a natural view of perceptual
judgment: Even though perceptual illusions occur, ordinarily we still
possess warrant for our perceptual judgments about the world. W.
thinks this is because our ordinary perceptual and self-attributing
judgments enjoy a kind of "default" warrant. Such a
warrant discounts the possibility of illusion, even when one has
gathered no supporting empirical evidence. Though if a reasonable
suspicion arises, the default no longer applies. But ordinarily our
judgments are "presumed innocent" of error until proven
(or at least evidenced to be) guilty; this in turn is rooted in our
communal practices, and is justified on pragmatic grounds (Wright
2000a, p. 152-153).



All this is important for B(3), since if W. grants (2) a
warrant in the absence of empirical investigation, it will be a
default warrant (at least in part). And this kind of warrant exists
only in *ordinary* cases. Thus, he grants this warrant only if
he assumes that there is no Dry Earth illusion where (3) merely
appears to be true. So in particular, in the context of the reductio,
W. allows an apriori warrant to the \*premises only if (3) is already
assumed as background. QED



Let us now consider some objections to transmission failure. One
accuses the advocate of conflating different types of warrant (Raffman
1998, Sainsbury 2000). Note here that, if the deduction fails to
*prove* the conclusion, this does not mean it transmits no
warrant at all. (Beebee 2001, Burge 2003). The objector accordingly
suggests that the deduction indeed transmits a warrant, though it is a
"thinner" warrant, i.e., a warrant that is weaker than
what a proof would bestow. But if a thinner warrant transmits, then
contra the advocate, the deduction indeed confers some apriori warrant
(albeit non-demonstrative warrant) onto (3). This, then, vindicates a
version of the reductio--for the intuition is that we cannot
warrant apriori a claim about the world *at all*. 



But is this intuition correct? To evaluate it we need further clarity
on what a "thin" warrant is. Some understand this as the
warrant failing as a warrant for equivalent propositions. For
instance, a non-empirical thin warrant for (2) may fail to warrant the
extensionally equivalent 'I am thinking that H2O is
wet' (Davies 2003b, p. 114 and 118). Alternatively,
"thinness" for W. may reflect that the warrant is not
something *earned* by gathering empirical or proof-theoretic
evidence. It is instead just a defeasible "entitlement"
that holds only in the ordinary cases (Wright 2003).



If the latter is what "thinness" consists in, then an
advocate could try to grant the transmission of a thinner
warrant--but still emphasize that transmission failure is the
rule when the warrants are thicker (Davies 2003b, but compare Wright
2003, p. 72). Yet an advocate might take a stronger stance by doubting
whether *any* thinner warrants transmits. After all, this
putative warrant dissipates immediately once any earnest doubt is
raised (Wright 2000b, yet contrast with Wright 2003; 2011).



A different objection to the advocate is that, despite appearances,
she ends up surrendering SK after all. This is because (3) is
empirical and it is conceded that (2) presupposes (3) (cf. Wright
2000, p. 151-152). And so, it is hard to see how (2) can be
warranted purely apriori if it presupposes empirical facts about the
world.



In response, at least one externalist has relinquished apriori
knowledge of (2), but emphasizes that some self-knowledge still
remains apriori (Rowlands 2003, ch. 8). In particular, an externalist
could still know apriori that:


5. If *E* obtains, then I am thinking that water is wet.



But for his part, W. thinks apriori knowledge of (2) should not be
surrendered. Instead, he claims we should not assume that the warrant
for (3) is inevitably empirical. For (3) ordinarily has a
non-empirical "default" warrant. So given that (2)
presupposes (3), a non-empirical warrant for (3) makes possible an
apriori warrant for (2). Even so, W. is quick to remind us that a
default warrant for (3) is too "thin" to *prove*
(3).



However, if the advocate grants an apriori warrant to (3), this may
succumb already to the reductio (Brown 2003; 2004, Sawyer 2006,
Brueckner 2006). For the absurdity was not that an apriori warrant
transmits; instead, it was in thinking that (3) can be apriori
warranted *at all*. 



Advocates can respond in two different ways here. One is to be neutral
on whether (3) is apriori warranted. A neutral position may suffice
for the advocate's purposes, since transmission failure occurs
if (3) is *presupposed*, regardless of whether it is apriori
warranted (Davies 2000). But such a response is not available to W.,
for he clearly thinks that (3) ordinarily has a non-empirical warrant.
Still, perhaps W. could soften this by reiterating that this is a
"thin" warrant bestowed by default; it is not a warrant
that is transmitted onto (3) by the deduction.



A final worry for W. is that he is conflating the psychological
phenomenon of SK with something merely linguistic or
"grammatical" (Snowdon 2012). If an externalist wishes to
explain how *knowledge of content* is possible, why would she
appeal to a *linguistic convention* to illuminate the matter?
It is clear, however, that W. never meant to forbid psychology from
having its say (Wright 2015, p.54). But it is possible that our
linguistic practices for crediting self-knowledge have mislead us
about the psychological facts. An analogy with ethical expressivism is
helpful on this score (cf. Wright 2015, p. 55) Instead of
investigating the "real moral facts," ethical
expressivists try to account for moral discourse, precisely due to the
suspicion that the discourse may not be grounded in bona fide facts of
the relevant sort. Similarly, there may be a suspicion in W. that a
robust psychological phenomenon of "armchair
self-knowledge" simply does not exist. Nonetheless, it may be
desirable for us to speak as if there was such knowledge, given our
aims and interests more broadly.


### 2.4 Reply 4: Self-Knowledge is Empirical



So far, the replies to the reductio have been "combative"
in that they seek to undermine some tacit or explicit premise therein.
Yet other responses are "concessive" in that they admit
that the reductio has a point. One concessive response is to reject
EXT in light of the reductio, though as we saw in section 1, EXT has
its own arguments to contend with. But a different concession,
considered in this section, is to forgo SK. (There is also a
"quasi-concessive" response, considered in section 2.5,
where the apriority of (3) is simply embraced rather than rejected as
absurd.)



Some incompatibilists indeed take the lesson of the reductio to be
that SK is false (see, e.g., McKinsey 2002). The sentiment is often
that SK should have been highly suspect from the start. Jacob (2004)
once expressed this well as follows:



> 
> [T]he contemporary philosophical situation is puzzling. On the one
> hand, few if any features of the special epistemic authority granted
> by both the traditional empiricist and the traditional rationalist
> pictures of introspective self-knowledge have survived recent
> philosophical scrutiny. On the other hand, several
> philosophers...assume that the alleged special epistemic
> authority granted to introspective self-knowledge by traditional
> epistemology can bear the burden of an argument against content
> externalism...I take externalism about the contents of an
> individual's thoughts...to be more plausible...than
> anything we may think about introspective
> self-knowledge...Imposing top down constraints...from the
> assumptions about the alleged epistemic status of introspective
> self-knowledge sounds to me like putting the cart before the horse.
> (pp. 401, 402)
> 



This attitude is encouraged by research from empirical psychology,
which suggests that self-knowledge is largely an illusion. (See for
instance Nisbett & Wilson 1977, Nisbett & Ross 1980, Gopnik
1983.) However, even if the research shows we are often ignorant of
our own minds, it does not follow that this is *most* often the
case. In fact, it has been argued that the current research does not
even preclude infallible self-directed judgments, such as those
described in section
 3.1
 (Parent 2016; 2017, ch. 2).



Still, there are other reasons to surrender SK, and this would be one
way to understand the lesson of the reductio. For instance, well-known
Quinean arguments exist against apriori knowledge, though this is not
the place to discuss these. (But see section 3 of the entry on
 Quine.)
 Ryle 1963, ch. 6 independently argued that self-knowledge is apriori;
such knowledge was instead achieved via empirical observation of
one's own behavior. Yet many contemporary philosophers balk at
this, since it at least underestimate the "authority" that
Oscar usually has in judging his own mental states (compared to
others' judgments) (Boghossian 1989, pp. 7-8). On the
other hand, given the psychological research mentioned above, a
neo-Rylean view may provide just the right amount of first-person
authority, to the extent that Oscar observes more of his behavior than
anyone else (Ludlow & Martin 1993; Martin 1994; McGeer 1996).



There is a more recent incarnation of this sort of view, supported by
the latest from cognitive science (Carruthers 2011). The claim is that
one interprets sensory input when attributing thoughts to oneself,
just as in attributing thoughts to others. However, the "sensory
input" behind self-attributions may include input from
interoception, proprioception, and the like. Nevertheless, the view
maintains that interpretation of "input" is central in
both first-person and third-person attributions of thought, which cuts
into so called "first-person authority."



A rather different line against SK derives from an externalist view
about concept possession. This view hypothesizes that possession of a
(non-empty) kind concept requires the ability to ostend or
*demonstratively identify* instances of the kind by perceptual
means (Brewer 1999; 2000a; 2000b). If so, then to possess the water
concept is already to know perceptually where (instances of) the stuff
resides. That in turn normally suffices for knowing that water exists.
So when it comes to the reductio, the absurdity stems from thinking
that (2) is apriori, since knowledge of (2) already rests on knowledge
of (3). So one can hardly learn (3) for the first time via knowledge
of (2)--the learning proceeds in the other direction.



In the acquisition process, however, the role of demonstrative
identification may be unclear. Nevertheless, a similar argument
against SK can be formulated as long as *some* kind of
empirical knowledge is needed to acquire the water concept. Indeed, it
is typically assumed that a person acquires a concept from
experience--which already portends that acquisition depends on
empirical knowledge. Yet if that's right, then even knowledge of
(2) has an empirical basis, since possession of the water concept
does. Hence, knowledge of (2) does not qualify as purely apriori .




In response, a defender of SK may concede that there is a
"training period" for acquiring a concept. Still, apriori
knowledge might be possible in that, once the subject has acquired the
relevant concepts, she can use them to gain *new* knowledge
without further empirical inquiry (Boghossian & Peacocke 2000, p.
2). But one problem is that EXT usually portrays concept possession in
a way that blurs the distinction between the "training
phase" and the post-acquisition phase (Hawthorne 2007, p. 213).
For the externalist thought experiments allow a subject to possess
(e.g.) the sofa concept even prior to being "trained" that
no armchair is a
 sofa.[19]




A final line against SK is that, if (1) is not apriori (as is
plausible), it follows that apriori knowledge of (2) is impossible
(Gertler 2004). After all, if (1) is not apriori, then Oscar
apparently cannot discriminate apriori between his water concept and
the Dry Earthian concept. So it seems incorrect to say that (2) is
something *known*. Now in fact, this raises the extremely
important question of whether such discriminations are necessary for
self-knowledge, but further discussion will be delayed until section
3. The discrimination sub-literature usually addresses the "slow
switching" arguments rather than the incompatibilist's
reductio.


### 2.5 Reply 5: A Transcendental Argument?



The last response to the reductio is to deny that the argument is a
reductio at all. Instead, this compatibilist embraces that EXT and SK
facilitate armchair knowledge of the world. Some externalists have
even offered independent arguments to that effect (Putnam 1981). But
these independent arguments are significantly more complex, having to
do with model theory and Skolem's "paradox." Such
things shall not be discussed here (but see the entry on
 skepticism and content externalism).



Yet as concerns the incompatibilist's reductio, it is unclear if
any externalist accepts it as an anti-skeptical argument (though see
Peacocke 1996, p. 152). Even if one believes that *some*
transcendental argument can succeed against skepticism, it is hard to
believe that the *incompatibilist's reductio* is a case
in point (cf. Davies 1998, p. 353).



Be that as it may, Warfield (1998) and Sawyer (1998) are often
interpreted as embracing the reductio qua anti-skeptical argument. But
the fact is that Warfield is mostly addressing Putnam's (1981)
argument. (Warfield mentions the reductio in passing, but he endorses
Brueckner's 1992 compatibilism from section
 2.1,
 instead of a transcendentalist reply.)



Sawyer, moreover, explicitly discourages those who interpret her
(1998) as embracing the reductio as an anti-skeptical argument:
"Remarks by others indicate that in general the question of
whether externalist arguments yield apriori warrants for beliefs about
environmental conditions is seen as synonymous with the question
whether we have an apriori refutation of external world skepticism. I
do not see the questions as synonymous" (2006, p. 150). Instead,
Sawyer's view seems similar to that of W., where speakers are
given a prima facie (albeit quite defeasible) warrant when ascribing
their own mental contents. Granted, Sawyer allows that given EXT, such
a non-empirical warrant can be transmitted to
 (3).[20]
 But it is not the kind of warrant that suffices to undermine
skepticism; the warrant is rather of the "thin" variety,
noted at the end of section
 2.3.
 Nevertheless, although Sawyer's view is not as radical as many
have thought, she would face similar obstacles as W.


## 3. Slow Switching Arguments



We have explored one argument against the joint truth of EXT and SK,
namely, the reductio to armchair knowledge of the world. But there is
a further group of arguments to the same incompatibilist end. Such
arguments rest on a different thought experiment, the "slow
switching" experiment, to bolster the incompatibility of EXT and
SK. In brief, the new thought experiment suggests that under EXT,
self-attributions of thought content are not sufficiently
*discriminating* to vindicate SK.



The slow switch thought experiment again features Oscar on
Earth--yet this time, we suppose he is unwittingly
*switched* to Twin Earth (e.g., during his sleep by a secret
government operative) (Burge 1988, Boghossian 1989). Upon his arrival,
he then takes up his usual activities, being none the wiser. Now the
externalist's intuition is that although Oscar's use
of'water' on Twin Earth initially refers to water on
Earth, over time it comes to denote XYZ. (The switch is thus a
"slow" one.) After all, Oscar will acquire the habit of
using 'water' in the presence of XYZ, and of using
'water' to converse with Twin Earthians about the stuff.
Yet if 'water' changes its referent, then (by the earlier
Frege-Carnap view) this signals a shift in intension or content. And
the change in content can occur without Oscar noticing. Indeed it
seems Oscar *cannot* detect the switch just from the
armchair.



What this indicates is that Oscar is unable to discriminate from the
armchair whether assertions using 'water' have a water
content versus a twin water content. As with the original Twin Earth
example, the lesson here is extended to *mental* content as
well. Hence, if a "water thought" is one that Oscar
expresses with help from the term 'water', the slow switch
experiment indicates that:


1. Oscar cannot discriminate from the armchair that his water thought
has a water content rather than a twin water content.



His inability to discriminate, moreover, seems pertinent to SK. As
Burge (1988, p. 653) puts it, (A) can easily suggest that SK is false
in Oscar's case, i.e.:


2. Oscar cannot know from the armchair what content his water thought
has.



Generalizing from this, (B) suggests that SK ends up false if EXT is
true.



In section
 3.1,
 we shall see that Burge denies that (A) entails (B). Yet in light of
his resistance, Boghossian (1989) formulates a different version of
the slow switch argument. This second version, known as the *memory
argument*, runs as follows. As before, suppose Oscar unwittingly
is subject to a slow-switch, so that the concept he expresses with
'water' at *t*1 denotes water, and the
concept he expresses at *t*2 denotes twin water. Then,
if *p* is a thought that Oscar uses 'water' in
expressing, the memory argument runs as follows (adapted from Ludlow
1993a):


1. If Oscar forgets nothing, then what Oscar knows at
*t*1, Oscar knows at *t*2.
2. Oscar forgot nothing.
3. Oscar does not know at *t*2 that he thinks
*p*.
4. So, Oscar does not know at *t*1 that he thinks
*p*. [from (a)-(c)]



Premise (a) is seen as a platitude about memory (though some deny
this; see section
 3.3).
 Premise (b) is regarded as stipulative, and premise (c) is thought to
be the lesson of the slow switch experiment. The thinking behind (c)
is this: Even if Oscar knows his water thoughts at
*t*1, yet these morph into twin water thoughts at
*t*2, he no longer knows at *t*2 about
any *water* thoughts. For Oscar no longer *has* water
thoughts at *t*2.



There are further variations on these slow switch arguments.
What's more, there ends up being multiple interpretations of the
initial thought experiment. (See the supplementary document,
 Variations on Slow Switching,
 for more details.) Nonetheless, all variations embody the same basic
thought: If EXT is true, then in a slow switch Oscar cannot
distinguish from the armchair a water content from a twin content.
This then forms the basis for why EXT precludes SK. Given the two
types of slow switch argument, note that sections
 3.3
 addresses only the second type, the memory argument. The remaining
sections, however, plausibly have some bearing on both types of
argument.


### 3.1 Reply 1: Self-Verifying Judgments



As concerns the (A) to (B) maneuver, Burge protests that this glosses
over an especially secure type of armchair self-knowledge. The claim
is that some judgments about one's own thought contents (a.k.a.,
"second order" judgments) are *self-verifying*.
Roughly, these are judgments where "thinking makes it
so"--where judging "I am now thinking that *p*
" is enough to make it *true* that one is now thinking
that *p*. Importantly, however, this self-verifying feature is
limited to one's *occurrent* thinking of *p* (in
contrast to any standing or dispositional thoughts).



To illustrate the self-verifying feature, consider the judgment:



> 
> 
> 
> |  |  |
> | --- | --- |
> | (W) | I am thinking, with this very thought, that water is wet. |
> 
> 
> 



Burge's idea is that in executing this judgment, one "runs
through" the very thought that the judgment is about. That is,
judging (W) necessitates thinking the thought that water is
wet--and thinking this thought is precisely what (W) contends. So
the very act of judging (W) suffices to render the judgment true. It
is in that sense that the judgment is self-fulfilling or
self-verifying. Besides Burge, self-verifying judgments were touted
around the same time by Davidson (1987; 1988) and Heil (1988; 1992),
though others have subsequently embraced them as well (e.g., Falvey
and Owens 1994, Gibbons 1996, Bar-On 2004, Parent 2007, 2017, chs. 3
and 7).



Nevertheless, the suggestion that certain judgments are
*infallible* can seem exceedingly strong. But for one,
infallibility does not imply that the judgment is
*indubitable*. A judgment could de facto be perfectly reliable,
yet the subject might still have some unanswered questions about it.
Second, it is crucial that 'thinking' is construed
minimally, in that to "think" that *p* is not
necessarily to *believe* that *p*. "Thinking"
that *p* just means having some mental state or other with the
content *p* --it does not imply any particular
*attitude* toward that content.



In light of things like Freudian repression, it can be easy to dismiss
Burge's view. But it is important that it pertains only to a
limited class of rather atypical judgments. For instance, it applies
only when the second-order judgment contains a
"self-referential" mechanism, expressed in (W) by the
phrase 'with this very
 thought'.[21]
 Moreover, the infallibility concerns occurrent judgments that
attribute the *co-occurrent* first-order thought. And the
judgment that (W) can be true even if the subject's mind also
harbors, consciously or unconsciously, a variety of other
thoughts.



Although self-verifying judgments are atypical, Burge still thinks
they are sufficient to block the inference from (A) to (B). For
apparently, they provide a kind of Cartesian access to one's own
thought-contents--meaning that (B) is false even if (A) is true.
Granted, self-verifying judgments are a rarefied kind of judgment, so
the view is not satisfying as a general view of self-knowledge
(Boghossian 1989, pp. 19-22). Still, the main goal was to block
the inference from (A) to (B), and self-verifying judgments seem to do
that.



Quite a detailed literature has ensued concerning self-verifying
judgments; the interested reader is directed to the supplemental
documents,
 The Epistemic Status of Self-Verifying Judgments,
 and
 A Problem with Critical Reasoning.


### 3.2 Reply 2: Relevant Alternatives



A different reply to slow switch arguments may have seemed obvious
from the start. It is that the slow switch thought experiment is a
bizarre piece of science fiction, and is simply irrelevant to whether
*we* know our own thoughts from the armchair. After all, unlike
Oscar, *we* are not the victims of covert switches. So how
could the experiment bear on our capacity for armchair
self-knowledge?



The point is often framed in terms of a "relevant
alternatives" epistemology (cf. Goldman 1976; 1986). The
suggestion is that in order to know that *p*, one does not need
to rule out *every* possible scenario where ~*p*. Rather,
it suffices just to rule out the "relevant alternatives"
where ~*p*. And ordinarily, deviant skeptical possibilities are
not among the relevant alternatives that a knower needs to exclude.
Thus, while driving along the countryside, one can ordinarily know if
one sees a barn--even without excluding the possibility of a mere
barn facade. For barn facades are ordinarily irrelevant.
In the same way, slow switch possibilities ordinarily are irrelevant
to knowing what content a thought has (Warfield 1992, Falvey &
Owens 1994, Gibbons 1996, Brown 2004, ch. 2). Accordingly, it is
normally unnecessary to rule out such a possibility in order to know
from the armchair one's own thought.



But what determines relevance exactly? A popular answer comes from the
epistemic contextualists (DeRose 1995; 2009, Lewis 1998; see also the
entry on
 epistemic contextualism).
 Contextualism in the first instance is a view about knowledge, yet it
implies that whether an alternative is relevant is determined by the
*evidential standards* in the context. Consider that in order
to know whether it is raining, normally one can just take a look out
the window. When engaging a Cartesian skeptic, however, that is
insufficient. For the skeptic "raises the bar" on the
evidence needed to know by imagining bizarre alternatives that he
wants ruled out, e.g., the possibility that you are dreaming.
Similarly, some compatibilists regard slow switching as a bizarre
skeptical possibility which makes exceedingly high the evidential
standards for knowledge (Hohwy 2002; Neta 2003 is also pertinent). So
if context makes that possibility relevant, one may lose the ability
to self-know from the armchair. Still, if switching possibilities are
irrelevant, contextualism says that even an externalist can know her
own thoughts from the armchair.



When first championing the memory argument, Boghossian (1989) noted
the reply from relevant alternatives, yet maintained that the slow
switch experiment still shows a conflict between EXT and SK. For one
can imagine cases where slow switching *is* a relevant
alternative. And in those cases, one could not rule out this
possibility just from the armchair. Even the relevant alternatives
account denies the externalist armchair self-knowledge in such a
scenario. Still, why does this reveal a problem with *our*
self-knowledge? If slow switching actually occurred on a regular
basis, it would be a relevant alternative that could not be excluded
from the armchair, and the externalist would lose SK. But to
acknowledge a possible scenario of this sort does not mean that EXT
and SK are *incompatible* (Warfield 1992). It shows merely that
if EXT is true, self-knowledge is *not necessarily* within
reach from the armchair.



In reply, some incompatibilists subversively suggest that switches
*do* occur on a regular basis (Ludlow 1995b; Butler 1997). In
section
 1,
 we saw that one "Twin Earth" scenario might occur in the
actual world: Recall the superficially indiscernible extensions of
'chicory' and 'endive', which are swapped
between British and Standard American English. An American ex-patriot
thus could be unwittingly fooled into denoting chicory when speaking
or thinking about "endive." Still, this seems like an
atypical case. But to the contrary, the potential for an undetected
switch might be as common as the potential for polysemy in the
language (Ludlow 1995b). Consider that between different philosophical
circles, the term 'pragmatism' denotes different yet
superficially similar philosophical theses. So thanks to unnoticed
switches between subgroups, one might be fooled into saying or
believing things about different kinds of pragmatism. Such variation
among linguistic subgroups seems entirely commonplace. It is the
*prevalence* of these switches, moreover, that makes them
relevant even if no actual switch occurs in a given instance.



In her defense, a compatibilist can observe that these cases are not
cases of *slow* switching, and the usual view is that contents
do not change in a "quick switch." (Though the
individuation of some cognitive processes may switch immediately; see
Clark & Chalmers 1998). Yet even if slow switches regularly occur,
this still does not show that EXT and SK are incompatible (Warfield
1997). It might mean that EXT and SK are not jointly true in our
world. Nevertheless, they still might hold in some other possible
world; so no incompatibility strictly follows.



Regardless, it may be troubling enough if an externalist cannot
*actually* have armchair self-knowledge (Ludlow 1997). It is
standardly agreed, moreover, that the externalist should concede one
type of armchair self-knowledge--namely, knowledge that is
discriminatory between water contents and twin contents, a.k.a.
"comparative knowledge" of content (Falvey & Owens
1994; see also Mendola 2008). But this may not be a huge concession,
since one may remain capable of knowing a self-verifying judgment that
(W) from the armchair, absent any comparisons with twin contents.
Besides, there is independent reason to reject such comparative
knowledge anyway (see Owens 1990; 1992).



A different issue is that if a compatibilist concedes SK when switches
are relevant, she may be conceding too much (Goldberg 2006a). For
there is a persistent Cartesian intuition that armchair self-knowledge
should be unaffected by skeptical hypotheses about the external world.
Following *Meditation Two*, even if an evil demon is deceiving
me, it still seems I can know what I am currently thinking. Yet the
slow switch experiment suggests that this Cartesian intuition is
mistaken. For if a slow switch hypothesis is relevant, then even a
relevant alternatives epistemology demands that we discriminate water
thoughts from twin water thoughts. Yet one is unable to do so from the
armchair. So apparently, some deviant hypotheses about the external
world *can* undermine armchair knowledge of one's own
occurrent thoughts, contra the Cartesian intuition. Something
important about armchair self-knowledge may be lost.



But a relevant alternatives compatibilist might still rescue the
Cartesian intuition. First, note that in many slow switch arguments,
the issue is not whether Oscar *knows that* he thinks that
*p* from the armchair; rather, it is whether Oscar *knows
what* he thinks. And unlike ascriptions of "knowledge
that," ascriptions of "knowledge what" are
appropriate only relative to one's *goals* or
*purposes* in a context (Boer & Lycan 1986, Braun 2006,
DeRose 2009, ch. 2,
 appendix).[22]
 Hence, whether it is apt to say "Oscar knows what he
thinks" partly depends on contextually salient goals or
purposes. Granted, if Oscar's goal is to discriminate between a
content and a twin content, then he cannot "know what" he
thinks from the armchair. However, it may be that for other
anti-skeptical purposes, Oscar can indeed "know what"
(Parent 2015b, 2017, chs. 5 and 10). For instance, suppose the skeptic
challenges Oscar on whether he knows the truth of anything with
certainty. Then, if Oscar points to his self-verifying judgment (W)
("I am thinking forthwith that water is wet") this could
count as meeting the challenge. It is a case where the *truth* of
his judgment is certain, even if its *content* is in question. So
at least relative to that goal, Oscar may know what he thinks (Parent
2015b, 2017, ch. 5).



Before closing this section, it is worth noting that compatibilists
sometimes prefer not to insist on the irrelevance of slow switches,
but rather to contest whether their relevance undercuts armchair
self-knowledge (Falvey & Owens 1994, Gibbons 1996, Butler 1997,
McLaughlin & Tye 1998a, Vahid 2003, Brown 2004, Morvarid 2015). A
variety of inferential principles might lead to the
incompatibilist's conclusion from the relevance of slow
switching. As a more noteworthy example, the principle here might be
some kind of "truth tracking" condition; cf. Nozick 1981
(Falvey & Owens 1994). On this approach, the slow switch argument
assumes that (W) does not express knowledge, since the subject S fails
to track the truth in the following sense:



> 
> 
> 
> |  |  |
> | --- | --- |
> | (TC) | *S* 's justification for the belief that *p* is
> such that, if some relevant alternative were true instead, *S*
> would still believe that *p*.  |
> 
> 
> 



According to (TC), *S* fails to know since her justification
would not divert her judgment, in a relevant scenario where the
judgment is false. However, if this is the principle operative in the
arguments, it seems they can be resisted (Falvey & Owens 1994).
Plausibly, we do *not* satisfy (TC) when it comes to
self-verifying judgments (see section
 3.1).
 For if we consider a counterfactual where I have twin water thoughts
in lieu of water thoughts, I *cannot* believe I have water
thoughts. A self-attribution expressed as "I am thinking that
water is wet" would inevitably attribute a twin water thought
instead. My self-attribution "tracks the truth" perfectly
in the counterfactual circumstances.


### 3.3 Reply 3: Externalism about Memory



Let us now focus our attention on the second version of the slow
switch argument, a.k.a. the memory argument, which is repeated here
for the reader's convenience. Where *t*2 is a
time after a slow switch, and *t*1 is a time before,
then:


1. If Oscar forgets nothing, then what Oscar knows at
*t*1, Oscar knows at *t*2.
2. Oscar forgot nothing.
3. Oscar does not know at *t*2 that he thinks
*p*.
4. So, Oscar does not know at *t*1 that he thinks
*p*. [from (a)-(c)]



(Slow-switching is a relevant alternative here, since it is assumed
that Oscar actually is slow-switched.) Now as one might expect, each
of the premises have been challenged by various compatibilists.
Regarding (a), some reject the suggestion that even if *p* was
known at *t*1, remembering *p* does not imply
*knowing* it at *t*2 (Bernecker 2010, ch. 3).
But even if remembering implies knowing, there are other ways Oscar
can lose knowledge besides forgetting (Brueckner 1997a; Burge 1998, n.
18). For instance, suppose Oscar knows he is driving through a
countryside with at least one barn, but some *defeating
condition* is introduced (e.g., he enters Barn Facade
County). Then, he may no longer *know* at *t*2
that there is a barn in his environs, even if he truly believes it.
That's because, although nothing has been forgotten, a defeating
condition exists at *t*2 that was absent at
*t*1.



An incompatibilist might try to stipulate that Oscar meets all the
conditions needed to know *p* on the basis of memory. However,
the compatibilist can reply that this is inconsistent with Oscar being
slow switched (Brueckner 1997a). For a slow switch *is* a
defeating condition, akin to entering Barn Facade County. In
that case, the incompatibilist's argument does not even get
started.



Alternatively, a compatibilist can attack the portrayal of memory
suggested by the argument. Here, one might claim that Oscar's
memory content is partly determined *not* by the Earthly
environment in which the memory was formed. Rather, memory content is
conditioned by the environment in which *recall* occurs (Ludlow
1995a; 1996; 1999; Gibbons 1996; Tye 1998; Bernecker 1998). This means
that, even if knowledge of a water thought was initially stored in
memory, what is "recalled" on Twin Earth is a twin water
thought. If so, then a slow switch causes a kind of memory failure,
since the knowledge initially stored in memory is not what is
recalled. (N.B., memories of second-order thoughts are the most
dialectically relevant here, though the literature often uses
first-order memories as examples, cf. Kraay 2002.)



This view of memory as "shifty" between different
environments may be a consequence of EXT. Apparently, we can just as
easily construct a Putnam-style thought experiment about Oscar's
and Twin Oscar's memories (Ludlow 1995a; 1996; 1999;). Moreover,
in the slow switch experiment, the presumption is that Oscar's
water thoughts *generally* change over to twin water
thoughts--including whatever (first- or second-order) thoughts
are stored in memory.



It may be quite unintuitive to see memory in this way, and we shall
attend to objections shortly. But it is worth noting that the view
allows an externalist to resist the memory argument. A compatibilist
might first grant that Oscar does not forget strictly
speaking--after all, we can assume no neurological impairment has
occurred in him. Yet she can add that Oscar loses some memory content
regardless, thanks to the slow switch. Even though Oscar does not
truly "forget," he has still lost knowledge by a different
route; premise (a) of the memory argument is thus false. (The
"shifty" view of memory has waned in recent years;
Bernecker 2004; 2010 relinquishes it in favor of something like
Burge's 1998 view, described below. Ludlow 2004 trades it for a
view where a memory is a temporally extended object, one which has
"stages" that hosts different contents at different times.
Yet see Burge 1998 n. 2 for remarks against such a view.)



The externalist view of memory can come as a shock; however, it might
enjoy some intuitive support (Tye 1998). For instance, suppose after
the switch that Oscar judges:



> 
> 
> 
> |  |  |
> | --- | --- |
> | W(+) | Water is the only thing I now drink; however, many years ago, I
> drank water fortified by gin. |
> 
> 
> 



Since (W+) is judged after the slow switch, the initial use of
'water' refers to XYZ. But does the second use of
'water' refer to XYZ? It seems so, since (W+) is
*comparing* his current imbibing habits with the past. Such a
comparison, of course, requires the liquid named in (W+) to be
constant. And since the initial use of 'water' denotes
XYZ, the second use of 'water' must also. The upshot is
that after the switch, the second clause in (W+) expresses a
memory that has "shifted" from water content to a twin
water content, as predicted by the compatibilist.



Still, the "shifty" view of memory remains controversial.
Consider that if Oscar's memory content is calibrated to Twin
Earth, so to speak, then some thoughts stored in memory will shift
from being *true* to being *false* (Hofmann 1995 (Other
Internet Resources), Brueckner 1997a, Nagasawa 2000). Oscar on Earth
expresses a veridical memory when he asserts:



> 
> 
> 
> |  |  |
> | --- | --- |
> | (W++) |  As a child, I thought that water was positively
> scrumptious. |
> 
> 
> 



However, after the slow switch, (W++) self-attributes a twin
water thought--and that thought is false. So what was a genuine
memory becomes displaced by a false memory.



Yet the objection may beg the question of how memory should function
(Ludlow 1996). For the issue is precisely whether memory is supposed
to preserve past contents across different environments. The
counter-suggestion is that memory instead offers information about
past events, in terms pertinent to the present environment (Ludlow
1996; 1999, Bernecker 1998). Ludlow (1999) provides an illustration:
"If at *t*1 I believed it was possible to drown
in water, memory will deliver a *t*2 belief that it is
possible to drown in twater--and good thing, too! Twater is no
less ...dangerous than water" (p. 167).



As a second worry, if Oscar's memory contents shift, has he
really forgotten nothing? A case can be made that the memory shifts
indeed constitute forgetting (Brueckner 1997a). For even though memory
offers up a similar substitute content, it seems clear that Oscar
fails to recall something about *water*. Yet a failed attempt
at recall *just means* that Oscar "forgot." If so,
then it is premise (b) rather than (a) which is the culprit in the
memory argument. (Even so, there may remain a different sense in which
Oscar does not forget; Brueckner 1997a, n. 21; see also Kraay
2002).



Nevertheless, it can be debated whether EXT entails the
"shifty" theory of memory. When Burge first presented his
Twin Earth experiment, he conceded that it does not show that
*all* mental contents satisfy EXT (though it suggests that that
is typically so) (1979, p. 92, passim). The contents of memory thus
might be an exception. And indeed, Burge (1993; 1998) endorses the
view that memory should "preserve" past thought contents.
So in a slow switch case, Burge holds that Oscar's properly
functioning memory preserves an Earthian thought content, so that the
very same content is available later for recall.



Accordingly, Burge rejects premise (c) of the memory argument: If
Oscar truly forgot nothing, then preservative memory means he knows at
*t*2 what he knew at *t*1. Per Falvey
& Owens (1994), Oscar's memory may not provide comparative
knowledge of content, i.e., knowledge that enables armchair
discriminations between water and twin water contents. But memory
still preserves knowledge of his thought at
*t*1--meaning that (c) is false. (The
incompatibilist might rejoin that (c) is stipulative in the thought
experiment; but in that case, Burge sides with Brueckner 1997a in
rejecting (b). Yet see Schroeter 2007 for a different issue in cases
where Burge rejects (c).)



Whether one accepts the "shifty" view of memory or not,
the debate is important to opening up different interpretations of the
slow switch thought experiment. For it complicates what effect the
slow switch has on Oscar's conceptual repertoire. The default
view is that the slow switch causes Oscar's water concept to be
*wholly replaced* by the twin water concept. But it may be
unclear why a slow switch *destroys* Oscar's water
concept, even as he becomes acquainted with twin water (Boghossian
1989; 1992a, Gibbons 1996, Burge 1998). More discussion of the issue
is found in the supplementary document,
 Variations on Slow-Switching.



As a final thought, memory may ultimately be a red herring in
defending incompatibilism. For suppositions about memory seem
inessential to the so-called "memory argument" (Goldberg
1997; 1999a; 2000a). After all, the key idea is that Oscar's
self-attributions can be open to more than one interpretation: Suppose
Oscar recognizes slow switches as relevant alternatives, and he
asserts 'I am thinking that water is scrumptious'. Then,
for all Oscar can tell from the armchair, this might express a water
thought or a twin water thought. Such "underdetermination"
in the interpretation is what Oscar cannot resolve without empirical
investigation. So already there is a problem with armchair
self-knowledge, absent any premises about memory.



When spelled out, this "memory free" slow switch argument
assumes the following "principle of knowing
identification:"



> 
> 
> 
> |  |  |
> | --- | --- |
> | (PKI) | If a subject *S* recognizes that there is more than one
> relevant interpretation of her assertions/beliefs--and *S*
> has nothing to decide between them--then *S* lacks knowledge
> of the content of her assertion/belief. |
> 
> 
> 



If Oscar satisfies the antecedent of (PKI), it may seem that he is
missing only *comparative* knowledge of content--i.e.,
knowledge that allows armchair discrimination between a content and a
twin content (Brueckner 1999; cf. Falvey & Owens 1994). And we saw
that many compatibilists are already willing to surrender that type of
knowledge. That's because Oscar's assertion "I am
thinking that water is scrumptious" might still count as one
kind of armchair self-knowledge (cf. section
 3.1),
 even if it is not of the comparative type.



However, (PKI) is applied to a specific kind of case, namely, where
(i) there is more than one *relevant* interpretation, and (ii)
the subject *recognizes* this (Goldberg 1999a). There, even a
relevant alternatives epistemology requires Oscar to rule out the Twin
Earth interpretation. Toward making this clearer, suppose that Oscar
is informed of the switches at some later time *t*3.
In that sort of case, (i) and (ii) will be satisfied. Thus if he
asserts "I am thinking water is scrumptious," he will be
aware of relevant alternative interpretations that he cannot rule out
from the armchair. Accordingly, even if his judgment is
self-verifying, it is tendentious to say he *knows* from the
armchair the content of his thought. (But for a rebuttal, see
Brueckner 2000.)



Notably, since the "memory free" argument is restricted to
a special sort of case, it does not show that EXT and SK are entirely
*incompatible* (Goldberg 1999a, p. 217; Goldberg 2000a). It
still suggests, however, that EXT precludes SK when certain skeptical
hypotheses are entertained--contrary to, e.g., the view in
*Meditation Two*. 


### 3.4 Reply 4: The Argument is Self-Undermining



As should be clear, slow switch arguments can be seen as skeptical
arguments, where the skeptic raises the possibility that *we*
are in Oscar's predicament. The externalist is thus asked to
rule out deviant thought contents from the armchair. Moreover, since
the skeptic thinks she cannot do so, he claims that the externalist
lacks armchair self-knowledge. But one sort of reply is that such
skepticism is *self-undermining* (Ebbs 1996; 2001; 2005;
Brueckner & Ebbs, 2012, ch. 12). The contention is that, assuming
EXT, the skeptic cannot both deny SK and be justified in accepting the
premises of his own argument. If so, skeptical slow switch arguments
end up being incoherent.



Consider that, since the skeptic wants to make a general point about
knowledge, he should see slow switch possibilities as relevant to his
own situation. The skeptic should not make an exception of himself,
re: his skeptical thesis. Hence, when the skeptic levies the slow
switch argument, his premises force him to say of himself:


1. If I am on Twin Earth, then my saying 'water is
scrumptious' expresses the thought that twin water is
scrumptious.
2. If I am on Earth, then my saying 'water is
scrumptious' expresses the thought that water is
scrumptious.



His premises also require him to say that:


3. I cannot know from the armchair which of the two thoughts is
expressed by 'water is scrumptious' (given that switching
possibilities are relevant).



The problem, however, is that (III) applies to 'water is
scrumptious' whenever the skeptic says it. Therefore, it applies
to the utterance as it occurs *in the consequent of* (II). So
if (III) is assumed, it follows that the skeptic does not know from
the armchair what thought is expressed by the consequent of (II),
hence, by (II) itself. Yet if it is unknown what thought is expressed
by (II), one can hardly be *justified* in accepting the
thought. Hence, the skeptic cannot simultaneously hold (III) and be
justified in accepting (II). (Ebbs also makes the analogous point
about the justification for (I), followed by similar objections and
replies. But for brevity's sake, we shall just consider
(II).)



The skeptic might offer two different replies to the self-undermining
charge. The first is that, although the exact content of (II) may be
unknown, the skeptic can still be justified in accepting (II)
(Brueckner 1997b). For it seems that (II) can be shown true, no matter
whether the skeptic speaks English or Twin English. After all,
regardless of what 'water' denotes, it is true to say
" 'water is scrumptious' expresses the thought that
water is scrumptious." Moreover, since the skeptic can recognize
this from the armchair, it seems he can be justified in accepting
(II), even while assuming (III).



But to the contrary, it is possible to imagine "weird
worlds" where (II) ends up false (Ebbs 2001). Consider a world
much like this one, where H2O fills the lakes and rivers,
etc., and where 'water' refers to H2O. The
difference is that 'Earth' in this weird world does not
denote the planet that the skeptic currently occupies. Rather, it
denotes Twin Earth. In that case, when the skeptic states (II), the
proposition expressed is that if he is on *Twin* Earth, then
asserting 'water is scrumptious' expresses the thought
that *water* (i.e. H2O) is scrumptious. (Remember
that 'water' in this scenario still denotes
H2O.) Yet if that is what (II) expresses, then the skeptic
says something *false*. And so, since the skeptic apparently
cannot exclude a weird world from the armchair, he cannot prove to
himself that (II) is true. So once more, the skeptic cannot
justifiably adopt (II) while assuming (III).



The skeptic has a second line of reply to the self-undermining charge,
which takes the form of a dilemma. Observe that 'water is
scrumptious' either expresses the content that the skeptic
thinks it expresses, or not. If it does, then (II) is true--and
so, in conjunction with (I) and (III), the slow switch argument
remains standing (Brueckner 2003). On the other hand, suppose that
'water is scrumptious' does not express the content that
the skeptic thinks it does. That just means he has a false belief
about the content of his first order thought. So he lacks knowledge of
its content (since knowledge requires truth). And thus SK is false in
this case too. Consequently, on either horn of the dilemma, SK is
threatened (Brueckner 2003).



Nevertheless, the skeptic could not justifiably claim that (I)-(III)
figure into a sound argument (Ebbs 2005). For at this stage, the
skeptic has conceded that (II) might not be true. Even so, it seems
that he can justifiably identify a different argument as a sound
skeptical argument, namely, the dilemma offered above (Brueckner
2007).



So has the skeptic escaped the self-undermining charge? There may
still be a question about the skeptic's adoption of (III). It
may seem that this is entirely justified, but why is that exactly?
Apparently, it is because the skeptic is justified in thinking that
'water is scrumptious' might express a different thought
than the one it actually expresses on Earth, viz., that water is wet.
Yet notice that this last bit assumes (II) (Brueckner & Ebbs,
2012, ch. 12). But at this stage, the skeptic has already conceded
that (II) might be false, due to the possibility of a "weird
world." So if (III) is justifiably believed only if (II)
is--and (II) was already surrendered--then the skeptic must
concede the justification for (III). So a kind of self-undermining
worry remains (Brueckner & Ebbs, ch. 12. For a response, see ch.
13).


### 3.5 Reply 5: Anti-Recognitionalism



A more programmatic critique of slow switch arguments resists its
assimilation of self-knowledge to perceptual knowledge. In particular,
the complaint is that slow switch arguments mistakenly assume that,
for Oscar to know what he is thinking, he must *recognize* what
he is thinking on the basis of some "inward observation."
Slow switch arguments then exploit the fact that what would be
"observed" is compatible with more than one thought
content. However, for one kind of compatibilist, such
"recognitional" models of self-knowledge are largely in
error. According to her, self-knowledge is unlike perceptual knowledge
in that it is not normally the product of any kind of recognition
(though she need not deny the existence of introspection altogether).
Some even take slow switch arguments as positive evidence for the
anti-recognitional view of self-knowledge (e.g., Moran 2001, p.
15).



"Anti-recognitionalist" compatibilism can be developed in
a number of ways. We have already seen some precedent in Burge
vis-a-vis self-verifying judgments (section
 3.1).
 For these judgments do not represent a "cognitive
achievement" (in the words of Boghossian 1989); they are
automatically self-verifying, whether the subject invests any
epistemic effort in them or not. Anti-recognitionalism has also arisen
in W.'s notion of "default" entitlement (from
section
 2.3).
 For W., a subject does not need a tight philosophical argument to be
entitled to her self-attributions; such entitlement is granted
automatically (unless there is special reason to withhold it).



A variety of other anti-recognitionalist views exist. E.g., there is a
neo-expressivist view which is gaining prominence (Bar-On & Long
2001, Finkelstein 2003, Bar-On 2004; 2006; 2011; 2012a, b; 2103,
Parent 2017, ch. 8). There are also views which utilize
agency-theoretic ideas to explain self-knowledge (Moran 2001, Heal
2002, Bilgrami 2006, O'Brien 2007, Coliva 2009). The interested
reader is encouraged to visit the entry on
 self-knowledge
 for more.


## 4. Other Issues with Externalist Self-Knowledge



There is a surprising number of further issues regarding EXT and SK.
Some of these consist in lesser-known incompatibilism arguments. For
instance, there is a kind of "inverted" memory argument
suggesting that, if Burge's self-verifying judgments count as
bona fide self-knowledge, then one's memory would be infallible
in ways that it is obviously not (Goldberg 2000b). In addition, it is
sometimes argued that EXT and SK preclude the standard analysis of
epistemic possibility. (Ebbs 2003; 2011. But see McLaughlin 2004.)



Questions about compatibility have been extended to more than just
knowledge of content. There is also a case to be made that EXT
precludes armchair knowledge of one's *attitudes* toward
those contents (Bernecker 1996, Gibbons 2001). Thus, even if it is
known that you are currently thinking that water is scrumptious, EXT
may preclude armchair knowledge that you *believe* this. For
what counts as "belief" might vary according to
one's linguistic community. In addition, new issues have arisen
in light of *externalism about qualia* (as held by Lycan 1987;
1996; 2001, Dretske 1995, Tye 1995). Briefly, if a quale is partly
individuated by the subject's environment, then it seems one
could not know that one had a quale of *fire engine red* unless
one antecedently knew the actual color of fire engines. But since the
latter is not knowable from the armchair, then it seems neither is the
former (Levine 2003, Ellis 2007).



Another set of issues concerns the metaphysics of mind. Some have
wondered if EXT and SK absurdly allow armchair knowledge of
Fodor's (1975) Language of Thought Hypothesis (Davies 1998).
Others have suggested that the Language of Thought Hypothesis
falsifies SK, assuming EXT (Boghossian 1989, p. 6, Bonjour 1991).
Further, some writers have worried that if one can know what one
thinks, then one can know *that* one thinks. If so, then the
ability to armchair know one's own thoughts would too easily
refute eliminativism about the mental (Dretske 2003a; 2003b; 2004,
Bernecker 1998; 2004b, Jacob 2004, Parent 2017, ch. 9; some papers in
Smithies & Stoljar 2012 are also relevant).



In addition, there is a burgeoning literature on whether EXT is
compatible with epistemic internalism, a view where knowledge or
justification supervenes on what's in the head (Pritchard &
Kallestrup 2004, Brown 2007, Gerken 2008; also cf. Chase 2001,
Brueckner 2002. Goldberg 2007a is germane too). Many of the issues
here turn on what kind of self-knowledge is allowed by EXT, and in
particular, whether such knowledge is discriminating enough for
justificatory purposes.



The debate on externalism and self-knowledge should continue to see
new developments. After all, as one writer observes:



> 
> in the last two decades several developments in the philosophy of
> mind, the philosophy of language, and epistemology make it worthwhile
> to reconsider semantic externalism's implications for
> self-knowledge...[T]hese developments include various versions of 2D
> semantics, the emerging popularity of so-called transparency views of
> self-knowledge...various doctrines pertaining to the semantics of
> 'knows' (such as contextualism, contrastivism, and
> pragmatic encroachment), a renewed focus on anti-luminosity arguments
> (deriving from the work of Williamson (2000)), and developments in the
> epistemology of testimony as well as in the epistemology of
> understanding. (Goldberg 2015b, pp. 7-8)
> 

 Moreover, the externalism/self-knowledge debate seems
not to be just a short-lived fancy; instead, it is arguably a
significant plot-point in the history of Western philosophy. This is
because:


> 
> [T]he issue reflects an important clash between philosophical
> paradigms before and after the linguistic (or conceptual) turn. On one
> hand, it is characteristic of Cartesianism that we can know contents
> introspectively, independently of knowing the external world. On the
> other hand, Frege taught us that content determines which external
> objects we refer to (or in Carnap's terminology, that intension
> determines extension). And as Putnam (1975, p. 218ff.) argues,
> Frege's idea seems to result in externalism: If content
> *determines* reference, then a difference in reference between
> Oscar and Twin Oscar shows a difference in content. That seems to
> hold, even if their narrow psychological states are the same. So if
> Frege's view leads to externalism, yet this precludes Cartesian
> knowledge of content, then apparently *one of these
> paradigm-defining ideas has to go*. Either Cartesians were wrong
> to say we can know contents just by introspection, or Fregeans were
> misguided to think that content is what determines reference. (Parent
> 2015b, p. 1346)
> 

 The debate on whether EXT is compatible with SK thus
deserves our continued, serious attention.