Martin Smith - - Mind What Else Justification Could Be1. Rational Self-Doubt and the Failure of Closure.
Joshua Schechter - - Philosophical Studies 2 Highlights of Recent Epistemology. Knowledge-Closure and Inferential Knowledge. Guido Melchior - - Croatian Journal of Philosophy 10 3 Adam Leite - - Croatian Journal of Philosophy 12 3 Knowledge and Deductive Closure. James L. White - - Synthese 86 3 - Frances Howard-Snyder - - Philosophia 36 1 Cornea, Carnap, and Current Closure Befuddlement.
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For example, since not - biv is entailed by h , I am in San Antonio, skeptics may argue as follows:. Tendentiously, some writers now call this strategy dogmatism. However, instead of K , Moore presupposed the truth of a stronger principle:. According to Dretske and Nozick, skepticism is appealing because skeptics are partially right.
They are correct when they say that we do not know that skeptical hypotheses fail to hold. For I do not track not - biv : if biv were true, I would still have the experiences that lead me to believe that biv is false. Something similar can be said about antiskepticism: antiskeptics are correct when they say we know all sorts of commonsense claims that entail the falsity of skeptical hypotheses.
Having gotten this far, however, skeptics appeal to K, and argue that since I would know not-biv if I knew h , then I must not know h after all, while Moore-style antiskeptics appeal to K in order to conclude that I do know not-biv. But this is precisely where skeptics and antiskeptics alike go wrong, for K is false. Consider the position skeptics are in. Having accepted the tracking view—as they do when they deny that we know skeptical hypotheses are false—skeptics cannot appeal to the principle of closure, which is false on the tracking theory.
We track hence know the truth of ordinary knowledge claims yet fail to track or know the truth of things that follow, such as that incompatible skeptical hypotheses are false.
One shortcoming of this story is that it cannot come to terms with all types of skepticism. There are two main forms of skepticism and various sub-categories : regress or Pyrrhonian skepticism, and indiscernability Cartesian skepticism.
At best, Dretske and Nozick have provided a way of dealing with the latter. Given the intuitive appeal of these principles, some theorists have looked for alternative ways of explaining skepticism, which they then offer as superior in part on the grounds that they do no violence to K. Consider two possibilities, one offered by advocates of the safe indication theory, and one by contextualists. Advocates of the safe indication theory accept the gist of the tracking theorist explanation of the appeal of skepticism but retain the principle of closure.
When we run the two together, we sometimes apply CR and conclude that we do not know that skeptical scenarios do not hold. Then we shift back to the safe indication account, and go along with skeptics when they appeal to the principle of entailment, which is sustained by the safe indication account, and conclude that ordinary knowledge claims are false.
But, as Moore claimed, skeptics are wrong when they say we do not know that skeptical hypotheses are false. Roughly, we know skeptical possibilities do not hold since given our circumstances they are remote. Skepticism might also result from the assumption that, if a belief formation method M were, in some situation, to yield a belief without enabling us to know the truth of that belief, then it cannot ever generate bona fide knowledge of that sort of belief , no matter what circumstances it is used in.
M must be strengthened somehow, say with a supplemental method, or with evidence about the circumstances at hand, if knowledge is to be procured.
This assumption might rest on the idea that any belief M yields is, at best, accidentally correct, if in any circumstances M yields a false or an accidentally correct belief Luper b,c.
On this assumption, we can rule out a method of belief formation M as a source of knowledge merely by sketching circumstances in which M yields a belief that is false or accidentally correct.
Traditional skeptical scenarios suffice; so do Gettieresque situations. Externalist theorists reject the assumption, saying that M can generate knowledge when used in circumstances under which the belief it yields is not accidentally correct. In highly Gettierized circumstances M must put us in an especially strong epistemic position if M is to generate knowledge; in ordinary circumstances, less exacting methods can produce knowledge.
The standards a method must meet to produce knowledge depend on the context in which it is used. Both tracking theorists and safe indication theorists defend agent-centered contextualism. For clarity, we might call them speaker -centered or attributor contextualists since they contrast their view with agent-centered contextualism. When the man on the street judges knowledge, the applicable standards are relatively modest.
But an epistemologist takes all sorts of possibilities seriously that are ignored by ordinary folk, and so must apply quite stringent standards in order to reach correct assessments. What passes for knowledge in ordinary contexts does not qualify for knowledge in contexts where heightened criteria apply. Skepticism is explained by the fact that the contextual variation of epistemic standards is easily overlooked.
Skeptics note that in the epistemic context it is inappropriate to grant anyone knowledge. However, skeptics assume—falsely—that what goes in the epistemic context goes in all contexts. They assume that since those who take skepticism seriously must deny anyone knowledge, then everyone, regardless of context, should deny anyone knowledge. Yet people in ordinary contexts are perfectly correct in claiming that they know all sorts of things. Furthermore, the closure principle is correct, contextualists say, so long as it is understood to operate within given contexts, not across contexts.
That is, so long as we stay within a given context, we know the things we deduce from other things we know. But if I am in an ordinary context, knowing I am in San Antonio, I cannot come to know, via deduction, that I am not a brain in a vat on a distant planet, since the moment I take that skeptical possibility seriously, I transform my context into one in which heightened epistemic standards apply. When I take the vat possibility seriously, I must wield demanding standards that rule out my knowing I am not a brain in a vat.
By the same token, these standards preclude my knowing I am in San Antonio. Thinking seriously about knowledge undermines our knowledge. To say that justified belief is closed under entailment is to say that something like one of the following principles is correct or that both are :. However, GJ generates paradoxes Kyburg To see why, notice that if the chances of winning a lottery are sufficiently remote, I am justified in believing that my ticket, ticket 1, will lose.
I am also justified in believing that ticket 2 will lose, and that 3 will lose, and so on. However, I am not justified in believing the conjunction of these propositions.
If I were, I would justifiably believe that no ticket will win. If a proposition is justified when probable enough, lottery examples undermine GJ. No matter how great the probability that suffices for justification, unless that probability is 1, in some lotteries we will be justified in believing, of an arbitrary ticket, that it will lose, and thus, by GJ , we will be justified in believing that all of the tickets will lose.
Even if we reject GJ , it does not follow that we must reject GK , which concerns knowledge closure. Consider the lottery example again. How justified we are in believing that ticket 1 will lose depends on how probable its losing is. Now, the probability that ticket 2 will lose is equal to the probability that ticket 1 will lose.
The same goes for each ticket. The probability of this conjunctive proposition is less than the probability of either of its conjuncts. Suppose we continue to add conjuncts.
Each time a conjunct is added, the probability of the resulting proposition is still lower. However, we need not reject GK on these grounds. Even if we grant that we justifiably believe that Ticket 1 will lose is true we might deny that we know that this proposition is true. We might take the position that if we believe some proposition p on the basis of its probability, nothing less than a probability of 1 will suffice to enable us to know that it is true. In that case GK will not succumb to our objection to GJ , for if the probability of two or more propositions is 1 then the probability of their conjunction is also 1.
We can reject GJ. Should we also reject J? The status of this principle is much more controversial. Anyone who rejects K on the grounds that K sanctions the knowledge of limiting or heavyweight propositions discussed earlier is likely to reject J on similar grounds: justifiably believing that we have hands, it might seem, does not position us to justifiably believe that there are physical objects even if we see that the former entails the latter.
Even if we reject this principle, it does not follow that justification is not closed under entailment, as Peter Klein pointed out. Instead, it might be p itself, which is, after all, a justified belief.
And since p entails its consequences, it is sufficient to justify them. Moreover, any good evidence we have against a consequence of p counts against p itself, preventing us from being justified in believing p in the first place, so if we are justified in believing p , considering all our evidence, pro and con, we will not have overwhelming evidence against propositions entailed by p.
A similar move could be defended against the tracking theorists when they deny the closure of knowledge: if we track p , and believe q by deducing it from p , then we track q if we take p as our basis for believing q. Looked at in this way, J seems plausible. There is a substantial literature on the transmissibility of evidence and its failure; see, for example, Crispin Wright and Martin Davies Proposition p has propositional justification for S if and only if, given the grounds S possesses, p would count as rational.
That p has propositional justification for S does not require that S actually base p on these grounds, or even that S believe p. Consider the following principles:. Clearly JD faces two fatal objections. First, we might fail to believe some of the things implied by our beliefs.
Second, we may have perfectly respectable reasons for believing something p , yet, failing to see that p entails q , we might not be aware of any grounds for believing q , or, worse, we might believe q for bogus reasons.
But neither difficulty threatens JP. First, propositional justification does not entail belief. Second, S might be propositionally justified in believing q on the basis of p whether or not S fails to see that p entails q , and even if S believes q for bogus reasons. As further support for JP , we might cite the fact that, if p entails q , whatever counts against q also counts against p.
The Closure Principle 2. The Argument From the Analysis of Knowledge 2. The Argument From Skepticism 5. Knowledge Closure Precisely what is meant by the claim that knowledge is closed under entailment? One response is that the following straight principle of closure of knowledge under entailment is true: SP If person S knows p , and p entails q , then S knows q. The conditional involved in the straight principle might be the material conditional, the subjunctive conditional, or entailment, yielding three possibilities, each stronger than the one before: SP1 S knows p and p entails q only if S knows q.
SP2 If S were to know something, p , that entailed q , S would know q. SP3 It is necessarily the case that: S knows p and p entails q only if S knows q. The qualifications embedded in the following principle construed as a material conditional seem natural enough: K If, while knowing p , S believes q because S knows that p entails q , then S knows q. But the following generalized closure principle covers deductions involving separate known items: GK If, while knowing various propositions, S believes p because S knows that they entail p , then S knows p.
In addition to rejecting K and GK , they deny knowledge closure across instantiation and simplification, but not across equivalence Nozick — : KI If, while knowing that all things are F , S believes a particular thing a is F because S knows it is entailed by the fact that all things are F , then S knows a is F.
KS If, while knowing p and q , S believes q because S knows that q is entailed by p and q , then S knows q. Let us turn to their arguments. The Argument From the Analysis of Knowledge The argument from the analysis of knowledge says that the correct account of knowledge leads to K failure.
But notice that we have: You know zeb You believe not-mule by recognizing that zeb entails not-mule You do not know not-mule. Put another way, the point is that the following reasoning is valid being an instance of strengthening the consequence : If R held, p would be true i. Again: if S knows p on the basis of R , and S believes q by recognizing that p entails q so that S believe q on the basis of R , on which p rests, together with the fact that p entails q , then S knows q on the basis of R and the fact that p entails q , as K requires.
For example, at one point Ernest Sosa discussed the following version of the condition: If S were to believe p , p would be true. It says an alternative A is ruled out on the basis of R if and only if the following condition is met: CRR were A to hold R would not hold. For Dretske, the negation of a proposition p is automatically a relevant alternative since condition CRA is automatically met; that is, it is vacuously true that: were p false, not-p might hold.
Second, we say that A is ruled out on the basis of R if and only if the following condition is met: SIR were R to hold A would not hold. Intuitively, it seems that if one knows the premises of an argument a priori and is able to validly deduce a conclusion from those premises, one would know the conclusion a priori as well.
This last point is on weaker ground, however, as discussed in Section 5b. The closure principle, now qualified to handle the straightforward counterexamples, has been employed in skeptical and anti-skeptical arguments, in support of a dogmatic refusal pay attention to evidence that counts against what one knows, to generate a paradox about self-knowledge, and for many other philosophical ends.
These uses are described in brief in this section, and in greater detail in later sections. If one really knew the ordinary common sense claim to be true, one could deduce the falsity of the skeptical claim from it and come to know that the skeptical claim is false by closure.
The fact that one cannot know that the skeptical claim is false as per the first premise demonstrates that one does not in fact know that the common sense proposition is true either.
See also Contemporary Skepticism. See Moore From the fact that one knows that she has hands and this is incompatible with a skeptical hypothesis under which her hands are illusory, one can infer, and thus come to know if closure is correct , the falsity of the skeptical hypothesis.
The closure principle can be used even in defense of a dogmatic rejection of any recalcitrant evidence that counts against something that one takes oneself to know. The argument runs as follows adapted from Harman :.
This result seems paradoxical, however, as most would claim that it is epistemically irresponsible to ignore all the evidence against what one takes oneself to know, simply because it is evidence against what one takes oneself to know. It is plausible though hardly obvious that one takes oneself to know each thing that one believes considered individually.
If this is conjoined with the argument above, it entails that one ought to ignore any evidence against what one believes. This seems to be an even more ill-considered policy. The closure principle also figures prominently in a paradox about self-knowledge and knowledge of the external world. It is now widely accepted that some thought contents are individuated externally. That is, there are some thought contents that one could not have unless one was in an environment or linguistic community that is a certain way.
On this view, one could not think the thought that water is wet were one not in an environment with water, or at least with some causal connection to water. Given content externalism, it seems we may argue as follows the argument is due to McKinsey :.
The conclusion follows from an application of the closure principle, but what makes this paradoxical is that it appears that the knowledge that is attributed in the premises depends on reflection alone introspection plus a priori reasoning , whereas the knowledge attributed in the conclusion is empirical.
If the premises are correct, and closure holds, I can know an empirical fact by reflection alone since I know it on the basis of premises than can be known by reflection alone. Something seems to have gone wrong and it is unclear which premise, if any, is the culprit.
It seems plausible to say that one knows one will not be able to afford a mansion on the French Riviera this year. However, that one will not be able to afford the mansion this year entails that one will not win the lottery. By the closure principle, since one knows that one will not be able to afford the mansion, and knows that this entails that one will not win the lottery, one must know that one will not win the lottery. However, very few are inclined at accept that one knows one will not win the lottery.
To determine whether someone is epistemically justified in believing something, one must do so from a particular point of view. One may consider the point of the view of the agent who holds the belief or of someone who possesses all the relevant information which may be unavailable to the agent. There are so many varieties of internalism and externalism that further generalization is perilous.
Hume famously argued that although we rely on inductive inferences, we have access to no non-question begging justification for doing so, as our only grounds for thinking that induction will continue to be reliable is that it always has been reliable. This is an inductive justification of the belief that induction is epistemically justified. If Hume is right, then a typical internalist will concede that beliefs based on inductive reasoning are not epistemically justified.
An externalist, however, might insist that such beliefs are justified, provided that inductive reasoning as a matter of fact is a process that reliably produces mostly true beliefs, whether the agent who reasons inductively has access to that fact or not.
On the other hand, an epistemic internalist might rate the beliefs of a brain in a vat or a victim of Cartesian evil demon deception as epistemically justified, provided that they were formed in a way that seems reasonable from the point of the view of the agent the brain in a vat , such as through the careful consideration of evidence evidence, albeit, that is misleading.
For the most part, internalist accounts of knowledge are those that appeal to an internalist conception of epistemic justification and externalist accounts of knowledge employ an externalist conception of justification.
Alternatively, one may be an internalist about justification and an externalist about knowledge, by rejecting the view that epistemic justification is one of the requirements for knowledge. Perhaps the greatest challenge to closure principles for knowledge comes from externalist theories of knowledge, notably those of Robert Nozick and Fred Dretske. It strikes many that some version of the closure principle must be true.
According to the tracking theory, to know that p is to track the truth of p. One knows that Albany is the capital of New York only if one would not believe it if it were false, and would believe it if it were true.
This is an externalist theory of knowledge because whether or not an agent satisfies the subjunctive conditions for knowledge may not be cognitively accessible to the agent. Let p be the belief that one is sitting in a chair in Jerusalem. Suppose one has a true belief that p. In close counterfactual situations in which one is sitting in Jerusalem, one does believe that p. Suppose, on the other hand, that one has a true belief that q. Hence, the belief that q does not count as knowledge. How does this relate to the closure of knowledge?
We may suppose that one can correctly deduce q from p. One may know that p , and know that p entails q and come to believe the latter by correctly deducing it from the former , and yet fail to know that q. One is that the tracking analysis of knowledge is plausible. The other is that the rejection of closure allows us to reconcile the following two claims, both of which seem plausible but had seemed incompatible: 1 we do know many common sense propositions, such as that I have hands , and 2 we do not know that skeptical hypotheses, such as that I am a handless, artificially stimulated brain in a vat , are false.
Both the skeptic and the Moorean anti-skeptic come up short here. The skeptic must deny our common sense knowledge claims and the Moorean must maintain that we can know the falsity of skeptical hypotheses. As long as we accept the closure principle, whether we are skeptics or anti-skeptics, we cannot maintain both that we know common sense propositions and that we do not know that the skeptical hypotheses are false, since we know that the common sense propositions entail the falsity of the skeptical propositions.
Knowledge of the truth of the common sense claims would, if knowledge is closed under known entailment, guarantee our knowledge that skeptical hypotheses are false. Citing our failure to know that skeptical hypotheses are false, the skeptic applies modus tollens and infers that we must not know the common sense propositions. The rejection of closure blocks this move by the skeptic.
This is not to say that there are not plausible counterexamples to the tracking account of knowledge. I may know my mother is not the assassin since she was with me when the assassination took place.
Less formally, we may put this as follows: one knows a given claim to be true only if one has a reason to believe that it is true, and one would not have this reason to believe it if it were not true. See Dretske This is an externalist account because whether an agent meets conditions i and ii above may be inaccessible to the agent.
Suppose one is in front of the zebra display at the zoo. One believes that one is seeing zebras on the basis of perceptual evidence. Furthermore, in the closest possible worlds in which one is not seeing zebras where the display is of camels or tigers , one would not have that perceptual evidence.
Consequently, one knows that one is now seeing zebras, on the basis of the perceptual evidence one is having. Consider, however, the belief that one is not now seeing mules cleverly disguised by zoo staff to resemble zebras. Hence, one would not know that one is not now seeing mules cleverly disguised to resemble zebras. One can know that one is now seeing zebras, one can correctly deduce from this that one is not now seeing mules cleverly disguised to resemble zebras, and yet fail to know that one is not now seeing mules cleverly disguised to resemble zebras.
Suppose that at five minutes past noon on Tuesday, Jones is suddenly struck dead by a bolt of lightning and is consequently no longer chair. Did one know at noon, five minutes prior to the death, that Jones was the chair? The example is adapted from Brueckner and Fiocco Dretske defines a sentential operator O to be fully penetrating when O p is closed under known entailment.
That is, O is penetrating if and only if: O p entails O q if p is known to entail q. Some operators are semi-penetrating. Within a range of cases, if p is known to entail q , then R is an explanatory reason for p entails R is an explanatory reason for q.
A reason that explains why Bill and Harold are invited to every party necessarily is a reason why Harold is invited to every party. The emphasis is crucial. A reason to paint the walls green is a reason not to paint them red, but may not be a reason to paint rather than wallpaper.
A reason to paint the walls green may be a reason not to paint the floor green, but it might be neutral as to the color. Consideration of ordinary demands for reasons shows that emphasis, or other contextual factors, determines a certain range of reasons to be relevant and a certain range irrelevant. Dretske says that no fact is an island and that various contextual factors will determine, for each operator, its relevant alternatives i.
See also Contextualism in Epistemology, Chapter 3, on Dretske and the denial of closure. On the other hand, some philosophers view the closure principle as so obviously true that, rather than reject it to accommodate a given theory of knowledge, they would reject the account of knowledge in order to keep closure.
This seems to point to the extreme plausibility of some form or another of the closure principle. Dretske a, agrees that such statements sound absurd, but maintains that they are true. They may violate conventional conversational expectations and they may be met with incomprehension, but they are not self-contradictory. It sounds a bit strange to say that the warehouse is empty, but has lots of dust, gas molecules, and empty crates in it.
The utterance may violate conversational rules, but the utterance might, despite all that, be true, if the concepts of emptiness and flatness are as described. So too with the abominable conjunctions if the attendant conception of knowledge is correct. Philosophers may always appeal to Gricean conversational implicatures to blunt the objection that their view entails absurd claims. Truth and conversational propriety are not one and the same. Paul Grice is the philosopher most closely associated with the view that communication is guided by various conversational maxims and that some utterances are conversationally inappropriate, even if true, because they invite misunderstanding.
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