MENTALISM AND SKEPTICISM

Clayton Littlejohn

cmlittlejohn@yahoo.com

The mentalists say that if two subjects are in the same non-factive mental states, these two subjects have the same evidence. I shall argue that if our evidence strongly supervenes upon our non-factive mental states and does not depend upon any further facts, we cannot have any non-inferential knowledge of the external world. Since we have non-inferential knowledge of the external world, we should reject both skepticism and mentalism.

INTRODUCTION

In this paper, I shall defend the crucial premise in an argument against mentalism.1 Mentalism leads

of a kind of external world skepticism. The skeptic is mistaken. As such, we should not be

mentalists.

For the purposes of this discussion, I shall assume that we have direct, immediate, or non-

inferential knowledge of the external world. Although this is not essential to their view, prominent

mentalists think that we do have this sort of knowledge of the external world. This anti-skeptical

view, I shall argue, is incompatible with mentalism. Assuming that the reader accepts this anti-

skeptical thesis, the reader ought to reject mentalism.

Mentalists defend a supervenience thesis about evidence:

M: If two subjects are in precisely the same non-factive

mental states, these subjects have precisely the same

evidence.

While mentalists are not committed to saying that evidence is propositional, it does seem that

evidence is propositional and (more importantly) it seems unlikely that the skeptical problem that I

think arises for mentalism does not arise for mentalism but only seems to when we speak as

1 Mentalism is the view defended by Conee and Feldman (2004). Mentalism is a thesis about justified belief that is committed to M and M+ if we build in additional assumptions that Conee and Feldman defend concerning the relationship between evidence for a belief and the justification there is to support that belief. The problem I raise here arises for anyone who believes that two subjects in precisely the same non-factive mental states have precisely the same evidence. This is a widely held view. See also Audi (2001), BonJour (1999), and Silins (2005).

evidence as if it consists of propositions.2 I shall assume for the sake of this discussion that evidence

is propositional and argue that M is false by arguing that M+ is false:

M+: Necessarily, if two subjects are in the same non-factive

mental states, p is included in the first subject’s evidence

iff p is included in the second subject’s evidence.

THE ARGUMENT

We cannot say that every proposition is included in everyone’s evidence, so there are two questions

to consider. What might prevent some proposition from being included in someone’s evidence?

What does it take to get something into someone’s body of evidence? Let’s first tackle the first

question. If p is not a piece of evidence, p will not be part of S’s body of evidence.3 S might treat p

as if it is a piece of evidence, but that is not obviously the same thing. As claims about evidence go,

this one seems pretty innocuous. This next claim is not so nearly innocuous. If p is not true, p is

not a piece of evidence (ET). Linguistic evidence suggests that evidence ascriptions are factive, so

the evidence suggests that evidence consists of only true propositions.

Consider two exchanges concerning an upcoming trial.

I. Scarlet: Does the prosecution have solid evidence against Mustard?

Green: The prosecution thinks it does. Here’s the evidence they have:

that he was the last one to see the victim alive, that he lied about

his whereabouts on the night of the crime, that his fingerprints

were on the murder weapon, and that he wrote a letter containing

details the police think only the killer could have known. That

being said, Mustard wasn’t the last one to see the victim alive, he 2 See Williamson (2000) and Neta (2008) for arguments for the view that evidence is propositional. In discussing Williamson’s view, Conee and Feldman (2008: 101) say that they need not deny that evidence is propositional in the course of explaining why they think their mentalist view is preferable to Williamson’s. 3 Some will say that nothing is a piece of evidence unless it is a piece of evidence for something and that no proposition can be evidence for something unless it raises the probability that the proposition that it is evidence for is true. I don’t disagree. I will talk about something being a bit of evidence without saying what it is evidence for, but that is not because I think there are propositions that are evidence without being evidence for something or other. As the class of propositions that does not do this seems rather small, this does not do much to exclude propositions from being propositions that are part of someone’s evidence.

did not lie about his whereabouts, and his fingerprints weren’t on

the murder weapon.

II. Scarlet: Does the prosecution have solid evidence against Mustard?

Green: People seem to think they do. Here’s the evidence they have: that

he was the last one to see the victim alive, that he lied about his

whereabouts on the night of the crime, that his fingerprints were

on the murder weapon, and that he wrote a letter containing

details the police think only the killer could have known. That

being said, I don’t know if he’s the last one who saw the victim

alive, I don’t know if he lied, I don’t know if his fingerprints were

on the murder weapon, and I don’t know if he wrote a letter

containing any details about the crime.

It seems to me that in (I), Green contradicts himself. It is hard to see how Green would contradict

himself in asserting what he did unless we were to assume (ET). In (I), all Green does is assert that

the negations of the propositions that he says are included in the prosecution’s evidence. If Green’s

assertion that so and so has p as part of their evidence is incompatible with his further assertion that

~p, that seems like a good reason to think that evidence ascriptions are factive. In turn, that seems

like a good reason to think that the evidence ascribed by true ascriptions of evidence must be true.

As for (II), it seems that Green either contradicts himself or says something that seems

contradictory in the way that Moorean absurd assertions are. If Green’s remarks are contradictory,

ET is true. Suppose Green’s remarks in (II) do not contain a contradiction but only seem

contradictory. Perhaps they are like Moorean absurdities. Would Green’s remarks in (II) be

absurd in the way that Moorean absurd assertions are if ET were not true? While ‘p but I do not

believe p’ is a Moorean absurdity, it would be strange to say that p must be believed by Green if

Green is to properly assert that p is included in someone else’s evidence if, say, we adopted a view

on which p is part of someone’s evidence whenever they have the right sort of non-factive mental

state with p as its content (e.g., an experience with the same representational content as the belief

that p or the belief that p). If instead we say that evidence requires knowledge or truth, then when

Green asserts that p is part of the prosecution’s evidence, Green is committed either to saying that

p is true or that p is known to be true by the prosecution. To assert ‘The prosecution is right in

saying that p but I don’t know if p is true’ or ‘The prosecution knows that p but I do not’, Green is

asserting something along the lines of more familiar Moorean absurdities such as Moore’s example

‘Dogs bark but I do not know that they do’. So, while I can see why Green’s seemingly

contradictory statements in (II) might be true, I cannot see why they would seem contradictory

unless we were to assume that ET is true. So, I submit that (I) and (II) provide us with linguistic

evidence for ET.4

To my knowledge, mentalists have not denied that ET is true. (Indeed, textual evidence

suggests that some prominent mentalists might accept ET.5) So far as I can tell, they do not have

to. Their view is that facts about evidence such as the facts about what evidence an individual has

supervene upon facts about the subject’s non-factive mental states. Lots of truths supervene upon

facts about a subject’s non-factive mental states (e.g., all the necessary truths and all the facts about

a subject’s non-factive mental states supervene upon facts about a subject’s non-factive mental

states). They can say that truths that do not so supervene are truths that are not included in a

subject’s evidence.

Let’s turn now to the second question. What does it take to get something into someone’s

body of evidence? The fact that p is a proposition is not enough. The fact p is a true proposition is

not enough. We do not all have the same evidence. According to Williamson, if S knows that p, p

is part of S’s evidence (KSE).6 I do not think that KSE is quite right. Suppose S acquires inductive

knowledge that q is the case. It seems counterintuitive to say that q is now part of S’s evidence and

that S’s evidence changes once S knowingly infers that q is true. I see nothing wrong with saying

that S’s stock of knowledge and body of justified beliefs change and change because S has used old

evidence to form new beliefs without thereby acquiring new evidence in the wake of forming new 4 For further defenses of ET, see Unger (1975). He argues that p cannot be your reason to believe or do something unless you know that p is true. 5 In describing what evidence one has for believing that there is a tree in the yard when one has a “treeish” experience of the sort that is indistinguishable from the veridical experience of a tree, Conee and Feldman (2008: 90) specify the subject’s evidence in terms of things that all happen to be true and things that could have been true had the subject been hallucinating. They go on to say that if we adopt the sort of view that McDowell adopts on which our perceptual evidence can include contingently true propositions about the external world (e.g., that this is a tree, that I see that this is a tree, etc…) they would say that the subject who undergoes a subjectively indistinguishable experience would not have such propositions as part of their evidence. This suggests that they do (sometimes) assume that ET is correct, otherwise they could say that the subject has the same evidence regardless of whether her experience is veridical or hallucinatory because there is no truth requirement on evidence. 6 Williamson (2000: 185). If I’m wrong and Williamson is right, then the problem I discuss here is much worse than I claim it is.

justified beliefs.7 If S comes to know, say, that the sun will come out tomorrow on the basis of

inductive grounds, I don’t think that prior to forming this belief S has evidence that entails that the

sun will come out tomorrow or the day after and I don’t think that after forming the belief S has

entailing evidence for this disjunctive proposition.

It seems that while knowledge that p is the case might not suffice for p’s inclusion in S’s

evidence, direct, immediate, or non-inferential knowledge that p is the case should suffice for p’s

inclusion in S’s evidence (IKSE). Perhaps the most obvious rationale for such a principle is this one.

A subject’s evidence should include whatever it is that they are entitled to reason from without the

support of additional premises. Anything that is known non-inferentially, immediately, or directly

can play that role of providing a basis to reason from without the need for some further basis. To

say that IKSE is false, you have to say that someone could know p non-inferentially and yet not be

entitled to reason from the premise that p for reasons having to do with the epistemic standing of

the belief that p is the case. Insofar as it seems that whatever it is that would prevent that belief

from being of sufficiently good epistemic standing to be used as a premise without further support

from further premises would prevent someone from knowing it without the use of additional

support from other beliefs, it is hard to see how IKSE could be denied.8 In terms of the dialectic of

the debate between the mentalist and myself, it would be an odd move for the mentalist to make to

say that they can resist the argument from mentalism to skepticism by insisting that we have less

7 This needs to be subject to an important qualification. By forming the belief that q, S does have new evidence for the claim that S is the sort of person who would believe q, who would bet that q, etc… If S believes, say, that the sun will rise tomorrow on inductive grounds, what I don’t think that S gets by forming this belief and coming to know that the sun will rise tomorrow is new evidence for, say, propositions obviously entailed by the proposition that the sun will rise tomorrow (e.g., that the sun will rise either today or tomorrow). Bird (2004) defends Williamson’s claim that p is included in S’s evidence even if S knows p via inference. 8 According to Kelly, “Evidence is what one has to go on in working out a view” (2008: 946). According to Silins, a piece of evidence is, “a reason which provides one with a justification to hold a belief, rather than merely explaining a belief” (2005: 378). It seems that anything we know non-inferentially would play the evidence-role as that role is understood by these authors. According to Conee and Feldman use essentially the same verbiage as Kelly when they remark, “One useful way to identify what we take to be a person’s evidence at a time is to say that this is the information or data the person has to go on in forming beliefs” (2008: 88). In describing what a subject’s “ultimate evidence” is, they say that the mark of ultimate evidence is that they can be evidence for a proposition without the need for further evidence for them and that the propositions in this body of evidence are, “the interface of one’s mind and the rest of the world” where “nothing available to introspection mediates between them and us” (2008: 92).

evidence than my overly generous account of evidence would have us believe.9 If two views differ

only insofar as the first insists that we have less evidence to justify beliefs about the external world

than the second, it seems that the second view will do as well or better than the first when it comes

to avoiding untoward skeptical consequences.

Now, let’s turn to the skeptical argument. Suppose, if only for the sake of reductio, that S

knows some contingent proposition about the external world, p, non-inferentially. It follows that p

is part of S’s evidence. According to mentalism, all of S’s non-factive mental duplicates have just

the same evidence that S does. At least one of S’s non-factive mental duplicates lives in a ~p-world.

At least one such mental duplicate has p as part of her evidence. If p is part of this subject’s

evidence, this subject lives in a p world. But, that contradicts our earlier claim that this subject

lived in a ~p-world. Thus, mentalism cannot say that we have non-inferential knowledge of the

external world because evidence requires truth and the possession of evidence requires nothing

more than non-inferential knowledge.

This argument shows that the mentalist cannot say that we have non-inferential knowledge

of the external world. Briefly, I want to note that we also have an argument for a kind of

justification skepticism. If S knows that she cannot know that p non-inferentially, S knows that she

should not believe p without inference from some further belief.10 If S knows that she should not

believe p outright without inference from some further belief, S might believe p non-inferentially

but she will not justifiably believe p. Thus, if S followed the argument above, S cannot justifiably

believe any contingent proposition about the external world without inference from some belief

about internal matters. I have not argued that the mentalist has to say that we can know nothing of

the external world, only that we can know nothing non-inferentially about the external world. So,

it seems that the argument for justification skepticism is really an argument that we cannot have

non-inferentially justified beliefs about the external world. The justification of our beliefs about the

9 It seems that (IKSE) is an obvious consequence of the view that says that whatever we non-inferentially justifiably believe will be included in our evidence since whatever we know non-inferentially will be non-inferentially justified. For a defense of the view that whatever is non-inferentially justifiably believed can be properly treated as a reason for further beliefs, see Fantl and McGrath (forthcoming). 10 Adler (2002) and Huemer (2007) defend the principle, which is implied by, but considerably less controversial than the principle defended by Sutton (2005) that says that you cannot justifiably believe any proposition that you do not know.

external world is possible, perhaps, but only by means of justified beliefs about our own non-factive

mental states.

RESPONSES

While I think that the thing to do is simply to deny mentalism, I doubt that this will be the

mentalist’s response. The mentalist might concede that we cannot have non-inferential knowledge

of the external world but insist that we can still have knowledge of the external world based on our

knowledge of the internal world. They could opt for a kind of traditional foundationalist view.11

This would let the mentalist soften the blow of the skeptical objection. While a mentalist might say

this, one of the leading mentalists rejects this sort of foundationalist view in favor of the kind of

foundationalist view that allows for the possibility of non-inferential knowledge of matters beyond

those pertaining to the contents and character of present conscious mental states.12 One reason

Feldman rejects the traditional foundationalist view is that he accepts an argument of Pryor’s.13

Pryor notes that if the traditional foundationalist view is correct, someone could know that, say,

there is a tree before her only if she based that belief on a belief that she is having a “treeish

experience”. However, it seems that cognitive science could discover that we simply do not have

these beliefs about our present conscious mental life to serve as the basis of beliefs about trees and

our relation to them. It seems that subjects that are just like us or very similar to us that formed

beliefs about trees without basing them on beliefs about “treeish experience” could know that there

is a tree before them when there is and they had the right sort of veridical experience. Thus,

traditional foundationalism is mistaken. The traditional foundationalist says that it is impossible to

know that, say, there is a tree before you if your belief that there is a tree before you is not based

on some further belief about your own mind (e.g., the belief that you are having a “treeish”

experience). This argument, which Feldman dubs the ‘cognitive scientist’s discovery argument’,

seems decisive to me as well. Pryor’s argument suggests that the traditional foundationalist view

must be mistaken and so the mentalist cannot soften the blow of my skeptical objection to

retreating to this traditional foundationalist view.

Inspired by Pryor’s argument, I shall offer one more argument. We might imagine that

cognitive scientists make additional discoveries about the nature of experience. Scientists discover 11 Feldman (2004) notes that BonJour (2003) is now an advocate of that view. 12 See Feldman (2004). 13 See Pryor (2000).

that part of the content of the experience you and I have when we look at a tree in good conditions

that there is a tree before us. Further, they discover that it is these contents that serve as the basis

of many of our beliefs about the external world. It seems that such experiences could provide the

basis for immediate judgments about trees. Indeed, cognitive scientists could discover that our

beliefs about the external world would typically be based on such experiential contents. Because of

ET, we cannot say that the subject who is not facing a real tree has as part of her evidence the

proposition that there is a tree before her. Because of mentalism, even if the subject were to

undergo a veridical perception, the subject in the good case would not have as part of her evidence

the proposition that there is a tree before her. Because of IKSE, this subject would not know non-

inferentially that the world is the way that her veridical experience represents it as being. Thus,

mentalism would be committed to saying that even if we discovered that the contents of experience

included contents that matched the contents of those non-inferential beliefs we formed about the

external world, those beliefs could not constitute non-inferential knowledge in the best possible

conditions. It seems that mentalism is not a genuine alternative to the traditional foundationalist

view that Feldman rejects on the basis of Pryor’s argument.

Of course, we do not need to wait for the results of actual or imaginary cognitive science

to cause trouble for the mentalist. Let me introduce some jargon. Let’s say that a proposition is an

i-proposition iff the truth of p supervenes upon facts about your non-factive mental states. Let’s say

that a proposition is an e-proposition iff p is not an i-proposition. Because our experiences have

veridicality conditions such that some non-factive mental duplicate of ours might have the same

experiences we do without having veridical experiences, the contents of our experiences includes

e-propositions. (There might be i-propositions included as well, but the contents of our

experiences are not exhausted by such propositions.) Because of ET, our evidence can never

include anything but i-propositions if the mentalist is right. Since e-propositions would be part of

our evidence if we knew e-propositions non-inferentially, it follows from mentalism that we never

know non-inferentially any e-propositions. The difficulty this view faces is related to the difficulty

that Pryor’s argument causes for the traditional foundationalist. If cognitive science discovered that

the bases of our beliefs about the external world included e-propositions, why shouldn’t we say that

it is possible for some beliefs based on e-propositions to constitute knowledge? Why would they

have to be based only on i-propositions? The only answer that comes to mind is that i-propositions

are true whether we are in the good case or a BIV but e-propositions are true in only some

situations where someone is just like us on the inside. I thought that people weren’t convinced by

the skeptical argument that says that we don’t know because someone in some remote possible

world could be just like us on the inside but mistaken. Yet, it seems that the mentalist would need

to appeal to this sort of skeptical argument to avoid saying that e-propositions can be the basis for

our beliefs about the external world.

In response to all of this, the mentalist might say that we do have just the kind of evidence

I’ve claimed that they say we cannot have (i.e., e-propositions). They will insist that the possession

of this sort of evidence doesn’t matter because it doesn’t make any epistemic differences we care

about.14 That is because the possession of such evidence can never make a difference to the

justificatory status of any of our beliefs. Suppose you know non-inferentially that some e-

proposition is true that some non-factive duplicate of yours believes mistakenly to be true. They

say that your belief and her belief have the same justificatory status. As such, the possession of e-

evidence is not epistemically interesting.

I suppose that I’m far less certain than the mentalists are that these sorts of comparative

epistemic judgments are correct. Although the view is controversial, it is widely believed that if p

is false, you cannot have sufficient warrant to assert that p is the case.15 If you should not assert that

p is the case for purely epistemic reasons but someone else is entitled to assert that p is the case, it

seems intuitive to me to say that this second subject’s beliefs concerning p are on better epistemic

footing than yours. It seems intuitive to say that if someone is warranted in asserting what you lack

warrant to assert, their belief is better justified than yours. Although the view is controversial,

some have argued that if you do not know that p is the case, you are not entitled to treat p as a

reason for action when deliberating about some p-dependent choice. If, however, you do know

that p, you are entitled to treat p as a reason for action.16 If you are not entitled to treat p as a

reason for action when deliberating about such a choice but someone else is, it seems that their

commitment to the truth of p is on better epistemic footing than yours. Again, it is tempting to say

that it follows from the fact that they are better justified in treating p as a reason for action that they

14 Conee and Feldman (2008: 99) say that the problem with McDowell’s view and views like his is that that the kinds of entailing reasons that they say we have for our external world beliefs can provide no more justification than is provided by the non-entailing reasons that we share in common with those who do not veridically perceive what we perceive but seem to do so because of illusion of hallucination. 15 A view defended by Williamson (2000) among others. 16 See Hawthorne and Stanley (2008) for a defense of this view.

must be better justified in believing p. This suggests that the intuition that the mentalist appeals to

in the hopes of showing that the possession of e-propositions as evidence is far from controversial as

it has implications that many would reject.

While we could deny that their relevant intuitions are correct, I should also point out that

these intuitions are irrelevant for the purposes of this discussion. The issue is not whether we are

better justified than our BIV counterparts, but whether we have the kind of knowledge that we

typically take ourselves to have. I have given an argument that makes no assumptions about the

comparative epistemic judgments that lead some to say that we are just as justified as our BIV

counterparts in our beliefs that suggests that mentalism leads to skepticism. If the mentalists are

absolutely convinced that we cannot have the kind of evidence I have argued we must have if we are

to have non-inferential knowledge of the external world, their insistence that we have the same

evidence as our BIV counterparts and their insistence that our beliefs are no better justified than

theirs does nothing to address the skeptical concerns raised here.

CONCLUSION

In this paper, I have argued that mentalism leads to a kind of skepticism. If the mentalists are right,

we could not have non-inferential knowledge of the external world. If Pryor is right, the

foundationalist view that says that we can have only inferential knowledge of the external world is

mistaken. If we’re both right, there is no non-skeptical view of any kind available to the mentalist.

While actual mentalists have said that they think the traditional foundationalist view that

allows only for the possibility of non-inferential knowledge of our own minds and knowledge of the

external world based on inference is mistaken, it seems that mentalists must opt for the sort of

traditional foundationalist view that it seems myself, the most prominent mentalist, and Pryor

thinks Pryor has refuted.

REFERENCES

Adler, J. 2002. Belief’s Own Ethics. Cambridge, MA: MIT University Press.

Audi, R. 2001. An Internalist Theory of Normative Grounds. Philosophical Topics 29: 31–45.

Bird, A. 2004. Is Evidence Non-Inferential? The Philosophical Quarterly 54: 252-65.

BonJour, L. 1999. Foundationalism and the External World. Philosophical Perspectives, 13: 229-49.

BonJour, L. and E. Sosa. 2003. Epistemic Justification: Internalism vs. Externalism, Foundations vs.

Virtues. Malden, MA: Blackwell.

Conee, E. and R. Feldman. 2004. Evidentialism. New York: Oxford University Press.

____. 2008. Evidence. In Epistemology: New Essays, ed. Quentin Smith: 83-104.

Fantl, J. and M. McGrath. Forthcoming. Knowledge in an Uncertain World. New York: Oxford

University Press.

Feldman, R. 2004. Foundational Beliefs and Empirical Possibilities. Philosophical Issues 14: 132-48.

Hawthorne, J. and J. Stanley. 2008. Knowledge and Action. Journal of Philosophy 105: 571-90.

Huemer, M. 2007. Moore’s Paradox and the Norm of Belief. In Themes from G.E. Moore, ed.

Susan Nuccetelli and Gary Seay, New York: Oxford University Press: 142-58.

Kelly, T. 2008. Evidence: Fundamental Concepts and the Phenomenal Conception. Philosophy

Compass 3: 933-55.

Neta, R. 2008. What Evidence Do You Have? The British Journal for the Philosophy of Science 59:

89-119.

Pryor, J. 2000. The Skeptic and the Dogmatist. Nous 34: 517-49.

Silins, N. 2005. Deception and Evidence. Philosophical Perspectives 19: 375-404.

Sutton, J. 2007. Without Justification. Cambridge, MA: MIT University Press.

Williamson, T. 2000. Knowledge and its Limits. New York: Oxford University Press.