1. Introduction

Does The Observation That Knowledge Ascriptions Are Context-Sensitive Provide The Basis For A Satisfactory Response To Scepticism?

There are several prior questions here, including the following. Is it the case i). that knowledge ascriptions are in fact context sensitive, ii). that contextualism is therefore true and iii). that a satisfactory response to skepticism is thereby derived? This also assumes that a response to skepticism is needed; it is also open to hold simply that if a theory is true, but it appears to open the door to skepticism, that this is just the way things are. I will begin with the first two questions before considering the last one.

2. The Case for Contextualism

2.1. DeRose

DeRose begins his most recent defense of contextualism by noting the support it derives from ordinary language. The main thesis of contextualism is that standards for knowledge are sensitive to context, and DeRose contends that we can observe these shifting standards in the way people commonly describe the epistemic status of themselves and others. He believes that whether we ascribe knowledge to ourselves and others can change because the relevant standards or the strength of the criteria for knowledge can change.

It is not sufficient to make this case by noting that the knowledge status of subjects changes. This change clearly occurs when the relevant circumstances including perceptual orientation of the subject change or when in fact the situation alters: these changes can give the subject new knowledge. If we are assessing whether subject S knows that there is a sheep in the meadow, the presence of a rock occluding the sheep for S will lead us to say no; if S moves such that this is no longer the case, we will be more likely to agree that S now knows there is a sheep present. This type of case is one in which knowledge changes because truth-relevant factors change; contextualism holds that knowledge changes when non-truth relevant factors change.

DeRose’s canonical example of how this might work is known as the Bank Case , but it also might be termed a ‘stakes-change’ case. There are two scenarios, LOW and HIGH. These denote two situations where a subject has the same information relating to a question, but different levels of interest in the answer. We are two assess in both cases whether S has knowledge of the answer.

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In LOW, S and his wife are outside the bank on a Friday evening wishing to deposit their paycheques, but note there are large queues. S was present at the bank in the last couple of weeks on a Saturday morning and it was open. S therefore says “I know the bank is open on Saturday morning” and suggests they return then.

In HIGH, the situation is the same as above with the exception that the couple have written a large check and if they do not deposit their cheques before Monday (we are to assume that the bank is closed on Sunday) there will be severe consequences. S will probably therefore say on Friday words to the effect of “I don’t know the bank is open on Saturday morning” and proposes to go and check. This DeRose claims means that S has altered his epistemic status in relation to the proposition even though no truth-relevant factors have changed. S still remembers seeing that the bank was open two weeks previously. What has changed is the risk assessment S makes of the consequences of error; conceivably the bank has changed its opening hours recently or even was only open on a Saturday for special reasons. It will be immediately apparent that one type of objection to this argument will claim that was has changed in HIGH is not the relevant epistemic standards, but warranted assertibility. It has not become appropriate to check the hours because the knowledge status of S has changed.

2.2. Lewis

David Lewis argues for a different variety of contextualism in which knowledge is defined as follows: “Subject S knows proposition P iff P holds in every possibility left uneliminated by S’s evidence”. This is modified with the caveat that ‘every possibility’ excludes those possibilities that S is properly ignoring. We do not claim that someone fails to know that it is daylight because they have failed to check whether someone has placed a set of lights outside their bedroom window overnight.

Assessing which possibilities may be properly ignored in this way is central to Lewis’s account. He proposes a set of rules to do this, including rules requiring that the actual situation and the one believed to obtain by the subject cannot be ignored; additionally any possibility being attended to is not properly ignored because it is not ignored at all – setting aside whether it should be, it needs to be considered because it involves the key concept of what is salient for S. These rules are context-sensitive and therefore represent a contextualist approach because different ranges of possibilities will become relevant in different contexts.

Which context is the relevant one is important. If A and B are discussing S, then there are two possible contextual sources of variation in knowledge ascription of S: the context of S and the context of A and B.

Lewis’s primary motivation in proposing this line is to defeat various skeptical lines including Gettier problems, lottery cases and skepticism in general. He views his claimed success in doing this as the primary commendation of his method. Since discussing this requires consideration of the skeptical angles, I will defer it to the final section on whether contextualism, if true, can defeat skeptical arguments.

3. Objections to Contextualism

3.1. Knowledge Destruction by Attention and Remote Conversations

The most significant type of problem with contextualism for many observers is apparently due to what might be termed ‘friendly fire’ from Lewis. DeRose discusses whether the salience line or attention can destroy knowledge, in that the more closely we consider a proposition, the more likely we are to cease to properly ignore a defeating alternative. This seems highly implausible; for one thing it would mean that the most careless and inattentive observers are the most knowledgeable. Yet Lewis seems to leave the door open to this: “Maybe epistemology is the culprit [that] robs us of our knowledge […] when we look hard at our knowledge, it goes away”.

There is a closely related objection that considers a scenario in which A and B are discussing whether S knows that P. The context changes for A and B in a way which means that they become much more epistemically demanding for S in relation to P. It seems extremely unappealing to now assert that S has ceased to know P, because S may have no knowledge of the conversation, and there may in fact be many such conversations taking place about S with wildly variant epistemic standards and in many distant locations.

DeRose may not be being entirely fair to Lewis here in that Lewis explains later he has been using some ellipsis for simplification; Lewis may wish to run an as if line here. However, DeRose avoids these problems by the incisive expedient of restricting the change in the epistemic status of S to whether S counts as knowing. This subtle but far-reaching change solves the A & B problem because it is entirely possible that different observers will have different views on whether S knows P.

It also solves the knowledge destruction by attention problem by denying it. In the Bank Case, one view would be that what has happened is not S previously knew P, where P is the proposition that the bank is open on Saturday mornings, and has now ceased to know it because S has now considered it more closely. DeRose can simply claim that in fact contextualism should hold that there are varying standards for knowledge in LOW and HIGH. S has knowledge sufficient for LOW in both scenarios and knowledge insufficient for HIGH in both scenarios: no knowledge has been destroyed. This response succeeds, but we should note how it restricts the theory, and also that the consideration of Lewis as the major proponent of contextualism requires modulation.

3.2. Why Privilege Ordinary Subjects?

DeRose clearly attached great importance to what people say. While some of his phraseology is strained, he can be allowed to be at least in the general vicinity of the way people talk. Yet why should we pay attention to this? We know that people are mistaken about an enormous variety of things on frequent occasions, and also that language is an evolving tool of imprecise nature and fundamentally pragmatic value. We say what works. Often what works well enough is shorter than a full description that would be tedious and unnecessary: “I knew it was daylight, provided no-one had set-up a lighting rig outside my bedroom” would needlessly eliminate one of an infinite number of irrelevant possibilities.

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This weakens the idea that studying language can lead to epistemological insight because there may not be much there. DeRose will respond to this by saying that the structures of language reflect deeper structures based on knowledge, and the evolution of language is indeed a survival of the fittest terminology that can only drive increased accuracy. However, this seems questionable particularly when seen in light of the objection considered in the next section, where DeRose is content to accept limited speaker competence.

3.3. Semantic Blindness

Some words, termed ‘core indexicals’, are very obviously contextual in behavior. They include “I”, “here” and “now”. The proposition “It is raining now” is false as I write; it may well be true for the reader. “Tall” exhibits similar behavior; a man may be tall on a tube train and not tall on a basketball pitch. Contextualism seeks to place “knows” in this category while its opponents, adherents of invariantism, deny this.

DeRose admits that since everyone agrees that “now” behaves contextually, but not everyone agrees that “knows” does so, some people must be insensitive to the true behavior of “knows” if contextualism is true. He attempts to defuse this by saying that invariantism has the same problem, because there are also some contextualists who suffer from semantic blindness in relation to the behavior of “knows” if invariantism is true: they falsely believe it reflects varying epistemic standards. This seems like a slightly over-clever maneuver and in any case inconsistent with the previous appeal to speaker competence.

4. How Does Contextualism Help With Skeptical Arguments?

Certainly all of the leading contextualists take themselves to be engaged in attacking skeptical arguments. DeRose bases his approach on a post-Nozick analysis, while Cohen attacks elements of Lewis’s line while supporting the overall approach.

4.1. DeRose

DeRose outlines an argument from ignorance that derives from Putnam’s Brain-in-a-Vat (“BIV”) scenario. This involves a modernized version of Descarte’s skeptical evil demon argument in which the subject is actually an envatted brain being fed with experiences identical to the ones that the subject apparently has in the real world. The argument runs as follows.

I). I do not know that not-H
II). If I, then I do not know that O
III). I do not know that O

H is a skeptical hypothesis, such as “I am not a BIV”, and O is an ordinary claim such as “I have hands”. Thus if knowledge is closed under known logical entailment, then I can only know that I have hands if I also know the heavyweight implication that I am not a BIV.

Nozick’s response is to attack the skeptical line by denying closure. DeRose wishes to retain Nozick’s Subjunctive Conditional Analysis (“SCA”) of knowledge, but also retain closure. He notes that the mention of the BIV hypothesis in the skeptical argument means that it has become salient, is being attended to and therefore by Lewis’s criteria, may no longer be properly ignored. The power of the argument then derives from the fact that actually, we cannot be 100.0% certain that BIV is false.

One advantage of SCA is that it correctly denies knowledge in this case, as DeRose points out. This is because the belief not-BIV would still be maintained even were BIV the case. In using SCA, Nozick will consider close and remote possible worlds in order to examine the counterfactuals. DeRose rightly notes that the selection of exactly which possible worlds constitute relevant alternatives is both central to SCA and potentially highly contextual.

DeRose will then contend that his modified Nozickean scheme retains closure, an intuitively plausible principle, and also avoids holding the abominable conjunction: ‘I know that I have hands and I do not know not-BIV’. DeRose does this by introducing comparative conditions, such as ‘tall’, and in the way previously mentioned. He thereby supports (II) by observing that even if we do not know whether A is tall or B is, if A is taller than B, we can assert that if B is tall then A is tall, in all contexts. Since contextualism holds that ‘knows’ behaves in the same way, this allows DeRose to retain the advantages of Nozick’s account without the claimed drawbacks.

4.2. Cohen

Cohen does not support Lewis’s attempt to solve all three of skepticism, the Lottery problem and the Gettier cases via his brand of contextualism. Kyburg’s Lottery problem relates how we are reluctant to say we ever know a particular lottery ticket will not win even though the number of tickets can be arbitrarily chosen; it can be so immense that the probability of it winning is less than the probability of the radio announcer reading out the wrong numbers – yet we still do not accept we know it is a losing ticket because there is no relevant difference between all the tickets and one of them will win. By Lewis’s rules of actuality and resemblance, that possibility may not be properly ignored.

Lewis also requires resemblances to be salient. Cohen makes the crucial inquiry of to whom the salience is relevant: the speaker ascribing knowledge to S or to S? And Cohen believes that this can avoid some skeptical issues with Lewis’s approach: Lewis should use the salience qualification to exclude the extreme skeptical possibilities. BIV cannot become salient because it is does not sufficiently resemble reality. It will be apparent that this is another benefit of the flexibility Nozick has built in to his account to allow for discussion as to which are the relevant possible worlds to consider in examining counter-factuals.

See Also:

The Structure And Content Of Truth For Davidson

Nozick’s Claim That Knowledge Is Truth-tracking: A Critical Evaluation

Spinoza’s Style Of Argument In Ethics I

What Is “Theory Of Mind?”


K DeRose, The Case for Contextualism, Oxford University Press, 2009
D Lewis, Elusive Knowledge, Australasian Journal of Philosophy, Vol. 74, No. 4; December 1996
K DeRose, Solving the Skeptical Problem, The Philosophical Review, Vol. 104, No. 1 (Jan., 1995), pp. 1-52
R Nozick, Philosophical Explanations, Harvard University Press, 1981
S Cohen, Contextualist solutions to epistemological problems: Skepticism, Gettier, and the Lottery, Australasian Journal of Philosophy, 76: 2, 289 — 306


Nozick’s Truth-tracking

1. Nozick’s Analysis of Knowledge

1.1. Introduction

Nozick is responding to Gettier’s claim that the traditional tripartite definition of knowledge as justified true belief is inadequate. Nozick’s analysis is specified by the following four conditions, which together are necessary and sufficient for knowledge:

1. p
2. Bap
3. ¬ (1) → ¬ (2)
4. (1) → (2).

The symbol → is non-standard: Nozick uses it for his relation of subjunctive conditionality. A → B means that if A were the case, then B would also B the case. This differs from logical implication ⊃. If it is true that A ⊃ B, then in all possible worlds in which A is true, so is B. Nozick uses A → B to mean the much more restricted case in which in the closest group of possible worlds in which A is the case, so is B. We are also using the following symbols: p is a proposition, a is a subject, B is the relation of belief so that Bap means that a believes p; ¬ is negation and → is Nozick’s subjunctive conditional.

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Dancy gives an illustration for which he cites Lewis of this crucial distinction. Lewis considers the conditional ‘if kangaroos had no tails, they would topple over’. This is a good illustration of A → B and not of A ⊃ B. In some possible worlds, the Australian tourist board gives the kangaroos crutches. This group of possible worlds is certainly more remote than the nearest possible world in which kangaroos have no tails and are unstable. So A → B is true but A ⊃ B is false because A does not entail B.

One of the terms for this analysis is ‘truth-tracking’ because the subject’s belief is co-variant with the truth of p; if it were the case that p then the subject would believe it and if it were not the case that p then a would not believe it. It has also been known as a counter-factual analysis because of the way in which it discusses near possible worlds distinct to the actual world in order to assess knowledge claims in the actual world.

1.2. Motivation

Nozick introduces his two new conditions (3) and (4) in order to handle cases which had not been soluble on the previous bases. Gettier cases involve erroneously scoped referencing in which the subject appears to have a justification for believing p and p is true and yet the situations appear to fall short of knowledge. For example: “Two other people are in my office and I am justified on the basis of much evidence in believing the first owns a Ford car; though he (now) does not, the second person (a stranger to me) owns one. I believe truly and justifiably that someone (or other) in my office owns a Ford car, but I do not know someone does.” Condition (3) eliminates this type of case as an instance of knowledge, which is a point in favor of Nozick’s analysis.

Nozick’s introduction of condition (4) occurs in the context of a skeptical scenario termed ‘Brain in a Vat’ (“BIV”) by Putnam. The subject is in fact a disembodied brain being stimulated by electrochemical means to have experiences; these being in the base case scenario all of the same experiences as in the current world. This skeptical hypothesis will produce important implications for Nozick’s analysis, to be discussed in the next section. The power of the hypothesis lies in the fact that while it is doxically identical to the actual world, almost everything believed in it is false.

As Nozick points out, his subjunctive analysis is related to but more restricted than the prior causal analysis. Under BIV, the subject can be brought to believe that BIV is true by being given appropriate stimulation. There is a good causal link between the event and the belief formation, but this cannot count as knowledge because it is fortuitous. Nozick can exclude this type of counterexample because it fails condition (4): in the close world to that of the BIV subject where he is not given the relevant stimulation, he no longer believes BIV although it is still true.

1.3. Skeptical Implications and Non-Closure

There is a major ‘heavyweight implication’ of Nozick’s analysis that is highly counter-intuitive. It will be instructive to see how he resolves it. The following principle, termed the closure principle, seems valid:

(CP): Kap & Ka(p -∃ q) → Kq.

The symbol -∃ is used to signify entailment, and so CP may be expressed as ‘if it were the case both that a knows that p and a knows that p entails q, then it would be the case that a knows q’; K is the two-place relation of belief used similar to B for belief previously.

This seems entirely plausible but Nozick uses BIV to argue that it is false. Let p be any everyday proposition such as ‘a is in London’. Let q be the negation of BIV. It is clear that p entails q, that a knows this entailment and that p is true and so under CP, a knows that BIV is false. Yet this is exactly the skeptical scenario that appears difficult to defeat.

Nozick’s dramatic response to this is to deny CP: “Knowledge is not closed under known logical implication”. He explains this by deriving it from the non-closure of (3): “That you were born in a certain city entails that you were born on earth. Yet contemplating what (actually) would be the situation if you were not born in that city is very different from contemplating what situation would hold if you weren’t born on earth.”

1.4. Methods

Nozick introduces a further refinement to handle what he terms the grandmother case. A grandmother comes to know that her grandson is healthy by seeing him. Were he not however, she would nevertheless be told that he was, in order to spare her distress. Nozick wishes to preserve this as a case of knowledge even though it fails condition (3).

This he does by adding the requirement ‘via method M’ to (2), (3) and (4). For a case to represent knowledge, M must not change in the relevant possible counter-factual situations. This means that the grandmother has knowledge in all the possible worlds in which she learns her grandson is healthy by seeing him, and does not in the possible worlds in which she relies on inaccurate testimony. This appears to be the correct result.

2. Objections to Nozick

2.1. Forbes

Forbes defends CP by putting pressure on Nozick’s line that the same method M must be used in (2), (3) and (4) in order to avoid incorrect knowledge ascriptions in the grandmother case. Forbes points out that M being reliable in the actual world where p is true does not entail that M is reliable in even the closest possible worlds where p is false.

The example given is of a reliable computer that can also check its own status. The proposition p is that the computer is functioning normally. The question is whether a subject can acquire knowledge that p by asking the computer to report its own status. If p, then this method M is reliable. However, if not p, then method M is by hypothesis no longer reliable. Thus there is no way to hold M constant while varying the truth value of p in order to assess whether the belief of the subject is co-variant with p.

Forbes allows that Nozick may have a response along lines similar to those used in an example that Nozick himself gives. This is of a vase in a box that is pressing a switch. The switch activates a holographic projector set to show a vase in the box. An observer passes all of (1) – (4) in respect of p, there is a vase in the box, and yet this is not a knowledge case. But Forbes holds that Nozick would then need to concede that the counter-factual analysis was inappropriate for all inferences and this would be arbitrary and severe for Nozick’s analysis. Perhaps Nozick here can instead adopt in some form Harman’s suggestion that all the lemmas be true.

2.2. Wright

Wright also attacks Nozick’s claim to have defeated the sceptical argument by introducing non-closure. He notes that using Nozick’s standard p and q (p = ‘I have a hand’; q = ¬ BIV) produces a problem for the ¬q scenario. Here, BIV is true and so p is false. We can assume that BIV is one of the relevant ¬p scenarios to be considered in assessing whether Kap. But if so, then subject a fails condition (3) because, even though p is false, Bap.

So Wright argues that Nozick must assume that BIV is not one of the relevant ¬p scenarios. And he further uses Nozick’s own argumentation against him with the following line, in which (I) represents ‘had it not been the case that I have a hand, then it would still not have been the case that BIV’.

(I): ¬p → q
(II): ¬q → ¬p
(III): ¬q → q

(II) is simply the statement that in BIV, I do not have a hand and then the reductio (III) follows by modus ponens from (I) and (II). As Wright points out, this could be seen as a refutation of the skeptic, but that line is not open to Nozick who wishes to agree that BIV is logically possible.

Wright allows Nozick the response of denying that transitivity holds for counter-factual conditionals. This would break the step to (III).

2.3. Garrett

Garrett defends Nozick against a purported counterexample given by Martin. Martin’s example considers a subject a placing a bet that pays if either of two horses wins. Subject a uses the unreliable method of finding out whether his horse won in the first race of simply cashing in his slip after the second race while avoiding any information about the first race. If his slip pays, he assumes that the first horse won whereas in fact it could have been the horse in the second race.

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Assume that the first horse did in fact win, and this is proposition p. The horse in the second race did not win. Condition (3) seems satisfied because ¬p → ¬Bap. Also, (4) seems satisfied. And yet this surely cannot be a case of knowledge because of the good fortune of a that the second horse did not win; a has failed to consider a relevant alternative.

Nozick’s response will be that in fact the possible worlds in which the first horse loses and the second wins are close enough that they have to be included in the assessment of whether Kap, whereas some possible worlds do not, such as one in which the betting machine has malfunctioned and is paying all slips. And then it is precisely the failure of Kap to track p in those close worlds that means (3) is not satisfied and this is not a knowledge case.

But Garrett has a refined version of this counterexample that he thinks is more dangerous to Nozick. Proposition q is that the father of person A is a philosopher; q is true. Proposition p is that the father of person B is a philosopher. Subject a uses the unreliable method M of forming Bap if a understands that q. It transpires unbeknownst to a that A and B are brothers, so in fact p. This fulfills conditions (1) – (4) but cannot be knowledge because it relied on the random unknown fact of A and B being brothers.

2.4. Gordon’s Response to Garrett

Gordon replies to Garrett’s objection by narrowing the scope of the problem of the father of A being a philosopher. Gordon notes that Nozick can appeal to his insistence that method M be held constant across the counter-factual scenarios. If method M means that a can legitimately infer facts about the father of A from knowing facts about the father of B and knowing that A and B are brothers, then M is reliable. It only becomes unreliable if extended to the general unrelated population. So can Nozick argue that this is in fact no longer M? For Garrett, the question becomes “why is it a requirement of knowledge that one have good grounds for thinking one’s method reliable?”

Gordon holds that Nozick has in fact replaced the tripartite analysis of knowledge as justified true belief (“JTB”) with his four conditions. Nozick is not therefore committed to JTB, and “even if Garrett can show a case in which one can meet Nozick’s conditions while using an unreliable method, he won’t have arrived at a clear counterexample to Nozick”.

2.5. Garrett’s Rejoinder to Gordon

Garrett responds by insisting “it is no presupposition of my counterexamples that it is necessary for knowledge that one have good grounds for thinking one’s method reliable if it is reliable”. Garrett agrees that if his counterexample shows unjustified true beliefs that meet all of Nozick’s conditions, and if JTB is required for knowledge, then he has found cases where Nozick ascribes knowledge incorrectly. However Garrett further claims that his counterexamples are valid against Nozick whether or not JTB is required. This seems strange however.

Garrett seeks to draw an analogy with the standard Gettier cases, saying that it is possible to explain why his father of A case is a counterexample to Nozick by showing the presence of unjustified true beliefs without insisting that justification is essential to knowledge. The idea seems to be that there is no entailment here. This seems true, but Garrett does not specify what alternate method he has to show that Nozick has falsely ascribed knowledge. Or alternatively Garrett may be thinking of a negative condition. Lack of justification is sufficient to disprove a knowledge claim, while the presence of justification is insufficient to prove a knowledge claim. This separation seems somewhat arbitrary though. In summary, Gordon’s defense of Nozick appears successful.

See Also:

Links Between Schopenhauer And Apocalypse Now

Ryle Contra Hidden Mental Processes

What Is “Theory Of Mind?”

‘Both A Black Raven And A Red Herring Confirm The Claim That All Ravens Are Black.’


  • R Nozick, Philosophical Explanations, Harvard University Press, 1981, (“PE”), p. 167 et seq.
  • J Dancy, Introduction to Contemporary Epistemology, Blackwell Publishing, 1985, p. 42
  • G Forbes, Nozick On Skepticism, The Philosophical Quarterly, Vol. 34, No. 134 (Jan., 1984), pp. 43-52, Blackwell Publishing
  • C Wright, Keeping Track of Nozick, Analysis, Vol. 43, No. 3 (Jun., 1983), pp. 134-140
  • B Garrett, Nozick on Knowledge, Analysis, Vol. 43, No. 4 (Oct., 1983), pp. 181-184
  • R Martin, Tracking Nozick’s Skeptic: A Better Method, Analysis, (Jan., 1983), pp. 28-33
  • D Gordon, Knowledge, Reliable Methods, and Nozick, Analysis, Vol. 44, No. 1 (Jan., 1984), pp. 30-33
  • B Garrett, Nozick and Knowledge: A Rejoinder, Analysis, Vol. 44, No. 4 (Oct., 1984), pp. 194-196