In the case of Pyrrhonian Skepticism, F includes every proposition, but we can generate different versions of Cartesian Skepticism by varying F. A prominent version of Cartesian Skepticism is external-world skepticism—i. Many contemporary philosophers take the canonical argument for Cartesian Skepticism to involve skeptical hypotheses and a Closure Principle CP.
One way in which a SH may satisfy a is by describing a situation where p is false, but this is not the only way. The connection between Closure principles and arguments for skepticism gets complicated if we countenance skeptical hypotheses which do not entail the falsehood of the proposition in question, and so in what follows we limit our discussion to those that do.
A crucial feature of CP is that it does not depend upon employing a stringent notion of justification. Suppose that positive justification comes in degrees, where the lowest degree is something like mere plausibility and the highest degree is absolute certainty. CP could be recast as follows:. There appear to be only three ways that one can respond to the CP-style skeptical argument: deny at least one premise, deny that the argument is valid, or reluctantly accept the conclusion—if neither of the first two alternatives succeeds.
Closure certainly does hold for some properties, for example, truth. If p is true and implies q , then q is true. It just as clearly does not hold for other properties, for example being surprising.
What about justified belief? Does Closure hold for it? First, notice that every logical truth is entailed by every proposition. If Closure held for justification, then we would have to say that everybody is justified in believing every logical truth provided that we are willing to grant that everybody is justified in believing at least one proposition.
Some logical truths are too complicated to even parse, let alone be justified in believing. The existence of very complicated logical truths also underlies another worry for Closure. For to every logical entailment between propositions there corresponds a logical truth: the material conditional with the entailing proposition in the antecedent and the entailed proposition in the consequent. Some of these logically true conditionals will be examples of propositions that we are not justified in believing if only because the consequent is too complicated for beings like us to even parse.
In that case, we might well be justified in believing their antecedents without being justified in believing their consequents. But it also appears that CP can easily be repaired. The skeptic can agree to those restrictions because the skeptical scenarios are posited in such a way as to render it obvious that our ordinary beliefs are false in those scenarios, and it is taken to be a contingent claim that S is in the actual circumstances as described in the antecedent.
There is one other important, required clarification of the restricted version of CP. It could be used to refer to a species of actually held beliefs—namely, those actually held beliefs of S that are justified. Or it could refer to propositions that S is justified in believing—regardless of whether S does indeed believe them. Following Roderick Firth, the distinction between actually held justified beliefs and propositions one is justified in believing, regardless of whether they are actually believed, is often marked by distinguishing between doxastic and propositional justification see Firth We are now in a position to ask: Does the restricted form of closure hold?
There are at least three types of argument against closure in the literature: alleged counterexamples, alleged unpalatable consequences, and incompatibility with allegedly plausible epistemological theories. In the remainder of this section we examine one exemplar of each of these.
Fred Dretske and others have produced cases in which they believe CP fails. Do you know that these animals are not mules cleverly disguised? The evidence you had for thinking them zebras has been effectively neutralized, since it does not count toward their not being mules cleverly disguised to look like zebras.
Dretske — Dretske is speaking of knowledge rather than justified beliefs, but that seems irrelevant since the issue concerns the supposed lack of a sufficient source of evidence or reasons for the claim that the animal is not a cleverly disguised mule.
The crucial thing to note about this proposed counterexample is that it works only if the Closure Principle entails that the very same source of evidence that justifies S in believing that the animals are zebras must justify S in believing that they are not cleverly disguised mules.
Thus, it could be held that this example could actually be used to support CP. Nevertheless, let us grant that the evidence for the claim that the animals are zebras cannot be used to show that they are not cleverly disguised mules.
Still, it could be argued that this would not force giving up CP. Such an argument could begin by recalling that CP claimed merely that whenever a subject is justified in believing p , then that subject is justified in believing q.
CP does not require that the subject have the same evidence for p as she does for q. No doubt this constraint sometimes correctly portrays the relevant evidential relationships when some proposition entails some other proposition. For example, suppose I have adequate evidence for the claim that Anne has two brothers. Then it would seem that the very same evidence would be adequate for believing that Anne has at least one brother.
But the defender of CP, and more particularly the Cartesian Skeptic, could point out that closure does not require this to hold for every case. There are two other possibilities. First, one may hold that when p entails q and there is some evidence e for p , it is p itself that is evidence for q. For example, it may be held that given that I have adequate evidence for believing that 2 is a prime number, I can use that very proposition that 2 is a prime number as an adequate reason for believing that there is at least one even prime.
See Klein , , and , but see below for reasons for doubting that this is a genuine possibility. Second, there are cases where the order is reversed because q serves as part of the evidence for p. For example, suppose that I am justified, ceteris paribus , in believing that pure water is present if I am justified in believing that there is present, at standard temperature and pressure, a clear, odorless, watery-tasting and watery-looking fluid that contains hydrogen and oxygen.
See Vogel , b for a discussion of Cartesian Skepticism and inference to the best explanation. For example, reconsidering the zebra-in-the-zoo case, it seems to be true that if I had some good reason to think that the animals are cleverly disguised mules, such a contrary would need to be eliminated before I would be justified in believing that the animals were zebras.
It could also be argued that CP has unacceptable consequences. Of course, one of those unacceptable consequences may well be Cartesian Skepticism itself, but to point that out in the present context would be dialectically unhelpful.
It has been argued, however, that CP by itself has far-reaching skeptical consequences. Notice that the argument for Cartesian Skepticism under consideration contains CP2 as an essential premise. If that were true, that would be a reason to be wary of CP, for it would be a much stronger principle than advertised.
The argument can be presented as a conflict between CP, on the one hand, and three other principles. Those three other principles are, allegedly, beyond reproach, and so CP is to be blamed for the conflict. The first principle in question may be thought of as enshrining the possibility of knowledge and justification by ampliative inference:.
Ampliativity would be true if, for example, we can be justified in believing the conclusion of an inductive argument say, that all emeralds are green on the basis of believing its premises say, that a properly selected group of emeralds have been observed to be green , without in addition being independently justified in believing any other proposition which, together with those premises, entails the conclusion such as, for example, the proposition that if a properly selected sample of emeralds have all been green, then all emeralds are green.
But there are two other possibilities. Maybe the evidential relation is reversed: whatever justifies us in believing q justifies us in believing p. Or maybe, we said, p itself, and not whatever justifies us in believing p , justifies us in believing q. The next principle goes directly against this possibility:.
Mere Lemmas : If S is justified in believing p on the basis of some evidence e , then p itself can justify S in believing some other proposition q only if e justifies S in believing q. Then you come to know that it is a hairless pet. But what about the example with which we introduced the idea that, sometimes, when e is evidence for p , then p itself can be evidence for q?
The example was the following: we can have adequate evidence for believing that 2 is a prime number, and then that proposition itself that 2 is a prime number can justify us in believing that that there is at least one even prime number.
But, when examined more closely, this is not an obvious counterexample to Mere Lemmas. For, what could our adequate evidence that 2 is a prime number be? Presumably, it would be that 2 is divisible only by 1 and 2. That just is the definition of what it means for 2 to be a prime number, however, so some may balk at the idea that it counts as evidence for the proposition in question rather than being identical with it.
In any case, it would not count as a counterexample to Mere Lemmas. For if we have no evidence for the proposition that 2 is a prime number, then the condition for the application of Mere Lemmas is not satisfied. Entailment : If p entails q , then q cannot justify S in disbelieving p.
The idea behind this principle is that if p entails q , then should q turn out to be true then things are as p says they are, and so we can hardly use q as evidence against p. We return to Entailment below, but first we show how these three principles are in conflict with CP. Assume, with Ampliativity, that a subject S is justified in believing a proposition h on the basis of some evidence e without having independent justification for believing any other proposition p such that p together with e entails h.
Notice that h obviously entails h or not-e. Therefore, by CP, S is justified in believing h or not-e. But, of course, e together with h or not-e entails h. Therefore, if S is justified in believing h on the basis of e , then there is a proposition which S is justified in believing and which together with e entails h. Notice that this is close to, but not quite, the negation of Ampliativity.
Independent of what? For all we have said so far, S might be justified in believing h or not-e on the basis of h , or on the basis of e itself. But, given Mere Lemmas, h cannot justify S in believing any proposition unless e does. Therefore, the only option left open, short of denying Ampliativity, is to argue that e itself justifies S in believing h or not-e. But that is incompatible with Entailment. For notice that for e to justify S in believing h or not-e is for e to justify S in disbelieving its negation, i.
But, of course, e and not-h entails e , and so the entailment principle has it that e cannot justify S in disbelieving e and not-h —i. The argument cannot, therefore, be taken to be a conclusive blow against CP. Finally, some epistemological theories are in conflict with CP. Roughly his account is this Nozick — :. Think of a guided missile tracking its target. If the target were to move left, the missile would move left. If the target were not to move left, the missile would not move left.
According to the tracking account of knowledge our beliefs must track the truth if we are to have knowledge. There is one important clarification of conditions 3 and 4 that is discussed by Nozick, namely, that the method by which S acquires the belief must be held constant from the actual world to the possible world.
So, we must require that the grandmother use the same method in both the actual and the near possible worlds, for, otherwise, condition 4 would exclude some clear cases of knowledge. Suppose S knows that there is a chair before her. Would she know that she is not in a skeptical scenario in which it merely appears that there is a chair?
Thus, either condition 4 is too strong or CP fails. There are some reasons for thinking that condition 4 is too strong. Consider, for instance, this case in the literature: You put a glass of ice-cold lemonade on a picnic table in your backyard.
You go inside and get a telephone call from a friend and talk for half an hour. It would seem that you could know that. Indeed, if it were false, that could only be due to some bizarre circumstance. The moral of this and similar cases seems to be that sensitivity is not a correct condition on knowledge.
CP2 claims that we are not justified in denying the skeptical hypothesis—in other words, that we are not justified in believing that we are not being deceived. What arguments can be given for CP2? It is tempting to suggest something like this: The skeptical scenarios are developed in such a way that it is assumed that we could not tell that we were being deceived.
But the skeptic must be very careful here. She cannot require that in order for S to know or be justified in believing something, say x , that if x were false, she would not still believe x. So the mere fact that there could be skeptical scenarios in which S still believes that she is not in such a scenario cannot provide the skeptic with a basis for thinking that she fails to know that she is not actually in a skeptical scenario.
But even more importantly, were that a requirement of knowledge or justification , then we have seen that closure would fail and, consequently, the basis for the first premise in the CP-style argument for Cartesian Skepticism would be forfeited. The usual way in which such conditionals are evaluated is by assuming that there is an ordering of possible worlds according to how much they resemble the actual world.
According to this semantics, subjunctive conditionals do not contrapose the contrapositive of a conditional if A, B is if not-B, not-A. Thus, suppose that we flip a coin to decide whether you or I will strike this match: heads you strike it, tails I do.
The coin comes up head, you strike the match and it lights. In this situation, it is true that if I had struck the match, it would have lit. The match might have failed to lit because it was wet while either of us struck it. Sosa [ 14 ]. Now, one initial worry about safety as a condition on knowledge is that, given that belief and truth are also necessary for knowledge, safety will always be in this context a true-true conditional that is to say, both its antecedent and consequent will be true.
This means that Sosa cannot accept the possible worlds semantics for subjunctive conditionals briefly sketched above, at least if we assume that every world is closer to itself than any other word. For when we have a true-true conditional, the closest world where the antecedent is true will be the actual world, and so every such conditional will be true and, hence, any condition formulated by such conditionals will be trivially satisfied.
But is safety a condition on knowledge? Several authors have thought that, just as there are counterexamples to sensitivity, there are counterexamples to safety as well. When I get to the crossroads, I ask Judy where the party is, and she tells me that it is down the left road. That case is a counterexample to safety insofar as we agree that I know that the party is at the house down the left road, and yet it could very easily have happened that I have that same belief on the same basis without it being so that the belief was true.
What else can be said for or against CP2? Problems for. BonJour's Anti-Skeptical Project. At least part of the justification for accepting the general probabilities would be that they make it possible to deduce the relevant particular probabilities.
But this would make the entire derivation question-begging. Alternatives to Skepticism. Skeptical arguments begin from the crucial presumption of skepticism about justification. They end with conclusions that deny we have any or more than the slightest bit of justification for beliefs that we antecedently took to be justified.
If reasoning is both top-down and bottom-up, then even if we think the skeptical arguments are deductively valid, we have a choice between accepting the conclusion or giving up one or more of the premises. What if we give up the crucial presumption?
If we give up the crucial presumption, then to be justified in believing that p does not require having a non-question-begging reason for believing that p.
One way of giving up this presumption is to give up the linear model of reasoning that is presupposed by the crucial presumption. Chloe's Objection: It can't be rational to give up a premise just because you don't like the conclusion that it leads to. It can't be rational to say to the skeptic that we give up the crucial presumption just to avoid the skeptical result.
Chloe is correct. But she has misstated the reason we have for giving up the crucial presumption. We start out thinking that some beliefs e. If we accept the crucial presumption, we must accept that all these beliefs are equally unjustified.
The issue is not what we would like to believe. The issue is what it makes the most sense to believe, where that is a rational judgment, not a judgment of what we would like.
What reasons are there for thinking that reasoning and justification are non-linear where there is no presumption that such reasons must fit a linear model? Coherence reasons for giving up the crucial presumption of skepticism in favor of a non-linear model of reasoning and justification:.
If our typical beliefs about ordinary physical objects or about the past and future are more justified than typical beliefs in Aryan history or astrology, then the crucial presumption is thrown into doubt because in combination with other shared premises, it implies that all those beliefs are equally unjustified.
If we can use the coherence of our memory beliefs as a good reason to believe our memory is reliable or incoherence as a good reason to revise our belief in our own reliability , then the crucial presumption is false.
If we can use the coherence of beliefs based on testimony as a good reason to believe that testimony is reliable or incoherence in testimony as a good reason to revise our belief in the reliability of testimony, then the crucial presumption is false. If inductive evidence provides us with good reason to regard induction as reliable, then the crucial presumption is false. In general, if we can use non-foundational, non-separable sources of belief to evaluate their own reliability, then the crucial presumption is false.
BonJour accuses exernalists and naturalists in epistemology of changing the subject. Is justification linear or non-linear? What do you think it makes the most sense to believe? The Problem of the Criterion A question of priority: 1 Which specific beliefs are justified? Responses to Skepticism 1. Descartes's Response The Cartesian Circle 1a.
BonJour's Cartesian Response 2. The Contextualist's Response 4. The Coherentist's Response 5. The Naturalist's Response 7. The Pragmatist's Response 8. If Descartes is correct, we are justified in believing: 1 that we exist when we are thinking it.
If BonJour's fallible foundationalism about a priori and empirical justification is true, we are also justified in believing: 2 the present deliverances of our a priori faculty i. I explain it with two questions: Question 1: Are we justified in believing the results of reasoning, when the premises are from the three categories above and the reasoning requires more premises than we can keep in mind at once?
For these reasons, transcendental arguments fail to deliver on their promise to overcome skeptical doubts. This is a preview of subscription content, access via your institution. Rent this article via DeepDyve. See also Stroud On whether or not transcendental arguments can be undogmatic, see Kuusela For a discussion of external world skepticism, see Greco See also Pritchard and Ranalli for discussion.
On other objections to transcendental arguments, see Stern , chapter 2. See also Chalmers On global and local skepticism, see Maitzen Maitzen argues that local skepticism cannot stay local. But his argument proceeds from the case of ethical skepticism or nihilism alone. For more on superposition, see Albert , pp.
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