I. Douven - 2005 - Lewis on Fallible Knowledge

8/11/2019 I. Douven - 2005 - Lewis on Fallible Knowledge

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Lewis on Fallible Knowledge

Igor Douven

Department of Philosophy, Erasmus University Rotterdam

[email protected]

Abstract

Lewis has offered a contextualist epistemology that he claims is non-fallibilist.

The present note aims to show that, while there seems to be a simple argument

for Lewis claim, the argument is fallacious, and Lewis epistemology is fallibilist

after all.

Contrary to what many philosophers hold, Lewis [1996] claims that fallibilism is mad-

ness (p. 550).1 Not that he has any deep argument to offer against the position. To

speak of fallible knowledge, Lewis thinks, just soundscontradictory (p. 549):

If you are a contented fallibilist, I implore you to be honest, be naive, hear it

afresh. He knows, yet he has not eliminated all possibilities of error. Even if

youve numbed your ears, doesnt this overt, explicit fallibilismstillsound wrong?

(p. 550)

I strongly doubt that these words will do much to persuade the faithful fallibilists. But

for now let us grant that there is something odd-sounding to overt, explicit fallibil-

ism (the significance of the qualification will become apparent shortly), and that wehave reasonto whatever precise extentto reject a theory of knowledge if it counte-

nances fallibilism of this sort. Then we have reason to reject Lewis own contextualist

theory of knowledge. For although explicitly meant to be non-fallibilist, it does not

escape (overt) fallibilism after all. So I will argue.

The centerpiece of Lewis theory is the following definition of knowledge: Sknows

that P iffSs evidence eliminates every possibility in which not-P . . . except for those

possibilities that we are properly ignoring (p. 554). What makes the theory contex-

tualist is that it depends on the context in which a knowledge attribution is made, or

being evaluated, whether a possibility is properly ignored. Exactly how context sorts

possibilities into those that are and those that are not properly ignored, Lewis specifies

by means of seven rules, which can be usefully classified as permissive and prohibitive

rules, respectively. The permissive rules are defeasible and tell us what possibilities

we may properly ignore; the prohibitive rules circumscribe the possible defeaters. An

example of a permissive rule is the Rule of Reliability, according to which we may

defeasibly properly ignore possibilities concerning error in reliable processes (such

as perception and memory; p. 558). An example of a prohibitive one is the Rule of

Actuality, according to which the possibility that is actual is never properly ignored

(p. 554 f). The rule that will be most crucial to our concerns is another prohibitive

rule, the Rule of Attention; according to this rule, a possibility not ignored at all is

ipso factonot properly ignored (p. 559).

1All page references given in parentheses are to Lewis [1996].

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A word on the notion of possibility: Lewis does not require that possibilities be

maximally specific; they just must be specific enough, where a possibility counts as

specific enough if it cannot be split into subcases that differ in some epistemologicallyrelevant way (p. 552). To borrow an example from Hawthorne [2002:243], the possibil-

ity that there is a dog in front of one does not qualify as a specific enough possibility

in Lewis sense, for it can be split in, for instance, a subcase in which one hallucinates a

dog while there is a dog before one anyway and a subcase in which the dog causes the

visual impression; from an epistemological viewpoint these are relevantly different

situations of course. Accordingly, such generally characterized possibilities as the

possibility that not-P and the possibility that Sis wrong about P fail to qualify as

sufficiently specific not-Ppossibilities in Lewis sense.

Already from the above outline it is evident that on Lewis theory a person can be

truly said to know even if she has not eliminated all possibilities of error, namely if

these possibilities are properly ignored in the context in which the knowledge attribu-

tion is made. Thus in one sense Lewis theory is undeniably fallibilist. But this is a sort

of fallibilismwhich we may label meta-linguistic fallibilismthat Lewis apparentlyregards as harmless and that at any rate he sees no need to oppose. In speaking about

Lewis theory, and specifically about what knowledge attributions people can make

under what circumstances on that theory, we are not ourselves attributing knowledge

to anyone. A fortiori, then, we are not attributing fallible knowledge to anyone. And

what Lewis abhors are attributions of fallible knowledge, utterances in which we as-

cribe knowledge to a person but in the same breath assert that the person might be

wrong. We in effect can take Lewis

He knows, yet he has not eliminated all possibilities of error (F)

to define this sort of fallibilism, as follows: an epistemology is overtly fallibilist iff,

according to it, (F) can, under some circumstances or in some contexts, be truly as-

serted. Notice that the difference with meta-linguistic fallibilism concerns assertions

of (F): meta-linguistic fallibilists do not claim that (F) never can be true; what they

claim, or at least what Lewis claims, is that it never can be truly asserted.

And prima facie Lewis seems to have successfully realized his intention to steer

clear of overt fallibilism. After allthe argument goesas soon as we mention any

uneliminated possibilities of error, we are attending to them, and thus, by the Rule of

Attention, are no longer properly ignoring them. By Lewis definition of knowledge, an

attribution of knowledge must then be false. Thus the mention of the uneliminated

possibilities of error in the second part of (F) makes false the knowledge claim made

in the first part of that sentence (supposing there are any uneliminated possibilities

of error; if not, the sentence is false anyway). Hence, on Lewis theory, (F) can never

be truly asserted. Or can it? I shall now argue that, indisputable though it may seem,

the foregoing little argument is fallacious, and Lewis is committed to overt fallibilismafter all.

Suppose one of our conversation partners utters the following sentence:

Shas not eliminated all not-P possibilities. (A)

Is there a sense of attending to a possibility in which this utterance should suffice to

have us attend to any uneliminated not-Ppossibilities? To attend to something means

to give heed to it, be aware of it, have it before ones mind. After hearing (A), we may

be expected to consider, or entertain, the proposition it expresses, that is, have some

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attitude toward that proposition (e.g., believe it, or doubt it, or wonder whether it is

true). Thus, arguably, the utterance will bring before our minds the proposition that

there exist not-P

possibilities uneliminated byS

s evidence. However, on the under-standing of possibilities explicated three paragraphs back, that proposition does not

qualify itself as an uneliminated not-P possibility, and the question was whether the

utterance of (A) ought to bring before our minds any such possibility.

The answer, plainly, must be negative, if only because (A) may be false, in which

case there isno uneliminated not-Ppossibility that could be brought before our minds.

More interestingly, it even seems hard to maintain that the utterance of (A) should

suffice to bring before our minds any uneliminated not-Ppossibilities if (A) is true. To

see why, consider that (A) may be both truly and sincerely asserted without even the

asserter having before her mind such possibilities. For instance, she may remember

from an epistemology course she once took that for all propositions like Pthere exist

so-called skeptical possibilities that cannot be eliminated by any amount of evidence.

Even when pressed, however, she might not be able to recollect a single one of those

possibilities. That is to say, she may know that uneliminated not-Ppossibilities existbut, at least at present, not have the faintest idea what they are like and therefore

cannot in any reasonable sense be said to have them, or some of them, before her

mind. Now, if (A) can be truly and sincerely asserted without even the speaker having

before her mind any not-Ppossibility, then why should hearing that sentence suffice

to bring before the listeners minds such possibilities? It would thus seem that utter-

ances of (A) are compatible with no person in the context of utterance attending to

any uneliminated not-P possibilities.

If correct, that spells trouble for our little argument against overt fallibilism, for

that clearly requires that there be some sense in which we are attending to unelimi-

nated not-Ppossibilities after the utterance of (A). According to that argument, after

all, it isbecause(A) is a constituent of

Sknows that P, though she has not eliminated all not-P possibilities (B)

that anyone who utters (B) or hears (B) being uttered must be attending to, and thus

cannot be ignoring and, ipso facto, cannot be properly ignoring, some uneliminated

not-Ppossibilities (provided there are any). Is there any way in which the argument

can be saved from a threatening quick refutation?

The best response I can think of goes something like this:

The notion of attending is not an altogether precise one. While it seems

correct that a person who entertains the proposition expressed by (A) need

not have before her mind any particular not-Ppossibilities, and thus need

not be attending to such possibilities inthatsense of attending to a pos-

sibility, she still may be said to be attending to them in some indirect,mediate wayvia the proposition that there exist not-Ppossibilities, so to

speak. To be a bit more precise, we might say that an uneliminated not-P

possibility is indirectly attended to by a person S iff it makes true the

proposition that there exist uneliminated not-P possibilities and Senter-

tains that proposition. The contrast, of course, is withdirectly attending

to a possibility, which does require that Shave that possibility before her

mind. So, while in the above example the utterance of (A) is compatible

with no person attending directly to any uneliminated not-Ppossibilities,

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it should suffice to have all such possibilities be attended to indirectly by

all participants to the conversation.

Preliminary to assessing the effectiveness of this response, let me note that thedistinction between possibilities directly and indirectly attended to is orthogonal to

that between possibilities that are and those that are not specific enough in Lewis

sense. In particular, it would be wrong to think that a possibility that is attended to

only indirectly must thereby fail to be specific enough. A speakers assertion of (A)

may hold true in virtue of the skeptical possibilities typically discussed in epistemol-

ogy courses, and surely these count as specific enough, whether or not the speaker

has any of them before her mind. Of course, if she is attending to them indirectly,

via the proposition that there exist such possibilities, she may be unable to specify

any one of them. But whether a possibility is specific enough, that is, whether it is in-

divisible in epistemically relevant subcases, is one thing; whether, or to what extent,

it is specified in a given context, or even specifiable by any of the speakers in that

context, is quite another. Further note that the fact that a possibility may be beforeones mind more or less clearly does not obfuscate the directly/indirectly attending

distinction, as a possibility that is attended to indirectly may notand, if it is attended

to indirectly only, will notbe before ones mind in any intelligible sense of having

something before the mind.

Grant that the directly/indirectly attending distinction makes sense. Then that

still only enables the Lewisian contextualist to ward off a first stab at the argument

against fallibilism. For now the question arises whether attending indirectly (in a

given context) to not-Ppossibilities uneliminated by a persons evidence is, on Lewis

theory, compatible with attributing knowledge ofPto that person (in the same con-

text). If it is, then the theory still does permit us to attribute fallible knowledge to a

personovertly and explicitly. For if while attending indirectly, but not directly, to

not-Ppossibilities uneliminated by a persons evidence I can truly say: She knows

that P, then surely I can also truly say: She knows thatP, yet she has not eliminated

all possibilities of error; the second conjunct of the latter sentence need not bring

anything to attention I am not attending to, nor need it make me attend differently

(quadirect/indirect) to anything I am attending to, when I say (truly, by supposition):

She knows that P.

Whether attending indirectly to not-Ppossibilities is compatible with the ascrip-

tion of knowledge ofPwill depend on whether possibilities that are attended to in-

directly, but not directly, can still be properly ignored, and thus, on what exactly is

implied by the Rule of Attention. Specifically, it depends on whether this rule can

plausibly be taken to imply only the first, only the second, or both, of the following:

(1) A possibility of error attended to directly is not properly ignored.

(2) A possibility of error attended to indirectly is not properly ignored.

We may suppose that it implies (1). Crucial for present purposes is only whether it

can also be held to imply (2). If Lewis epistemology is not to be committed to overt

fallibilism, then, as we just saw, the answer had better be yes.

It might seem that the fastest way to end this discussion would be simply to stipu-

late that, regardless of whether the Rule of Attention was meant to imply (2), from now

on it does. Unfortunately, however, this is not an option. Lewis theory is supposed

to be a contribution to descriptive epistemology; its aim is to provide an analysis of

the semantics of know. As for any such analysis, its adequacy is to be judged on

the basis of how well it accords with linguistic practice. Consequently, we will have

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to see whether there is any linguistic evidence indicating that the Rule of Attention,

when taken to imply (2), is part of the analysis of knowledge.

The Rule of Attention, says Lewis, was devised to account for a very particular typeof linguistic evidence: My Rule of Attention . . . [was] built to explain how the skep-

tic manages to sway uswhy his argument seems irresistible, however temporarily

(p. 561). The skeptic manages to sway us, Lewis thinks, by directing our attention to

some skeptical possibility or possibilities.2 Im willing to grant that this is so,3 and

that this gives support to the Rule of Attention under some interpretation of that rule.

The question is whether it supports the rule if that is taken to (also) imply (2).

Skeptics typically paint quite colorful pictures of the possibilities they suppose to

convince us that we can know nothing or next to nothing. We are, for instance, asked

to imagine that were brains in a vat, floating in a fluid of nutrients, our nerve endings

connected to a super-fast computer, the computer programmed in a certain specific

way, and so on and so forth. Whatever the exact details of such stories, they are

obviously meantand usually succeedto have us attend directly to some specific

uneliminated (and non-eliminable) possibility or possibilities of error; they do notjust try to make us aware that there are such possibilities. Hence, our (presumed)

responses to them at best provide support for the Rule of Attention interpreted as

implying (1).

There may well be evidence for the Rule of Attention from sources other than

our responses to the skeptic. I shall now argue, however, that if this rule is taken to

imply (2), then linguistic evidence rather seems to indicate that it is notamong the

rules governing our usage of know.

Ironically, a first indication in this direction comes from the practice that moti-

vated the Rule of Attention. Skeptics typicallypaint colorful pictures of uneliminated

possibilities of error, I said. As far as I know, however, this is how theyinvariably

proceed.4 Be that as it may, it is certainly true that no skeptic has ever tried to con-

vince us of her position just by stating that, however good our evidence, we might bemistaken about virtually anything we claim to know, that is, by merely directing our

attention to the proposition that for virtually all of our knowledge claims there exist

possibilities of error not eliminated by our evidence. Yet if the Rule of Attention im-

plied (2), that should work. To appreciate this, note that from Lewis theory it follows

that, for almost any contingent proposition P, if in some context we can truthfully

attribute knowledge ofP to a person S, we must in that context be ignoring certain

not-Ppossibilities not eliminated by Ss evidence. That means that if in such a context

someone were to say to us: Despite all your evidence, there are still uneliminated

possibilities of error for just about any proposition you claim to know, that would

have us consider the true proposition that there are uneliminated possibilities of error

for virtually any proposition we claimed to know and, consequently, would make us

2

Lewis seems to have in mind here what Williams [1999] terms the Cartesian skeptic; next to this sortof skeptic, Williams identifies anAgrippan skeptic. Very roughly, the latter argues that any attempt to

justify a claim must eitherlead to an infinite regressorto dogmatismorto circular reasoning, and that

therefore the possibility of knowledge cannot be maintained. Since at least prima facie her argument

does not seem to make any appeal to skeptical possibilities, it may well be that concessive responses

to the Agrippan skeptic cannot be explained by invoking the Rule of Attention. Note, however, that the

Agrippan skeptical argument has force only if justification is a necessary condition for knowledge, and

this Lewis denies (p. 551). So presumably he would say that those who are persuaded by that argument

are simply misguided about what is required for knowledge.3But see Feldman [1999], Oakley [2001], and Rysiew [2001] for alternative explanations of the way we

tend to respond to the skeptic.4That is to say, this is how Cartesian skeptics seem to invariably proceed; see note 2.

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attend indirectly to a non-empty class of uneliminated possibilities of error for most

of them. If, then, the Rule of Attention were to imply (2), these possibilities would

no longer be properly ignored and we could, accordingly, no longer truly ascribe theknowledge to ourselves we previously did. Hence, it would follow that merely men-

tioning that we might be wrong about virtually anything we claim to know suffices to

make false virtually all attributions of knowledge we made or would otherwise make

to ourselves.

It is certainly telling that skeptics typically go to great lengths in arguing for their

position where, if the Rule of Attention implied (2), they could achieve their goal

so easily. As intimated, however, this is only anindication against the truth of the

supposition that the rule implies (2), not conclusive evidence against it; skeptics, after

all, might concoct their fantastical stories merely for rhetorical or literary purposes.

Better evidence doesnt seem hard to come by, though. For consider that we simply do

not findas surely we ought to if the Rule of Attention implied (2)that just raising

the possibility that a person is mistaken about a given proposition, without giving

the least specification of a scenario that could explain how she might have come topossess the evidence she possesses were the proposition false, generally suffices to

make people reluctant to attribute knowledge of that proposition to her or to make

them withdraw a previous attribution of knowledge of the proposition. Suppose,

for instance, you tell someone you know that Gore lost the 2000 elections, and that

person says: You might be wrong there. Would there be anything improper or out

of the ordinary if you replied: Well, I might, but I dont think I am? It seems not.

I rather suspect that, were you to retract your knowledge claim in response to the

other persons utterance, most people would take that to indicate that the claim was

not sincerely made in the first place, or perhaps that you suffer from some form of

character weakness. In any event, we will not normally consider such a retraction as

being a simple consequence of the semantics of knowwhich it would be if a rule

implying (2) were among those governing our usage of that verb.I am not saying that we alwaysare willing or able to maintain an earlier knowledge

claim once our attention has been pointed to the proposition that there are possibili-

ties of error not eliminated by our evidence. Usuallyjust saying that I might be wrong

will not suffice to make me retract a claim to the effect that I know the first moon land-

ing was in 1969. In some situations, however, like for instance a situation in which my

life, or (less dramatically) my winning a large prize, depends on not falsely asserting

when the first moon landing occurred, mentioning that possibility just mightsuffice.

But evidence showing that undersomecircumstances we do retract knowledge claims

after the mentioning that there are uneliminated possibilities of error is utterly un-

helpful to Lewis, for, it will be remembered, overt fallibilism makes no stronger a

claim than that (F) sometimes, insomecontexts, can be truly asserted.

In sum, if the Rule of Attention is to be justified by reference to our usage of

know, then the rule must be taken to imply (1) at most. But if it does not im-

ply (2), then, it was argued, the rule cannot offer any help in preventing the attribution

of knowledge in a context in which the attributor merely entertains the proposition

that the subjects evidence fails to rule out some possibilities of error, and does not

have before her mind any particular uneliminated possibility of error. So in that case

the rule does not preclude that, in some contexts, (F) and other sentences similarly

attributing knowledge to a person while making one attend, but only indirectly, to

possibilities of error uneliminated by the persons evidence, can be used to make true

assertions. We must thus conclude that Lewis is committed not only to meta-linguistic

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fallibilism but also to overt fallibilism, madness or no.5

References

Feldman, R. [1999] Contextualism and Skepticism, Philosophical Perspectives

13:91114.

Hawthorne, J. [2002] Lewis, the Lottery and the Preface,Analysis62:242251.

Lewis, D. [1996] Elusive Knowledge, Australasian Journal of Philosophy 74:549

567.

Oakley, I. T. [2001] A Skeptics Reply to Lewisian Contextualism,Canadian Journal

of Philosophy31:309332.

Rysiew, P. [2001] The Context-Sensitivity of Knowledge Attributions,Nos 35:477

514.

Williams, M. [1999] Skepticism, in: J. Greco and E. Sosa (eds.)The Blackwell Guide

to Epistemology, Oxford: Blackwell, pp. 3569.

5I am greatly indebted to Tim Oakley for generously providing extremely valuable written comments

on an earlier draft; I am also grateful to Christopher von Blow and to two anonymous referees for

this journal for very useful suggestions for improvement. Versions of this paper were delivered at the

Universities of Amsterdam (Free University) and Leuven and at Erasmus University Rotterdam; I thank

the audiences on those occasions for their helpful questions and remarks.

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I. Douven - 2005 - Lewis on Fallible Knowledge