Varieties of Skepticism
KNOWLEDGE SKEPTICISM about a domain of potential belief D is the view that there is no knowledge of the propositions in D, but there may be some justification for believing some rather than others or for believing some to be more probable than others.
JUSTIFICATION SKEPTICISM about a domain of potential belief D is the view that no proposition P in D has some specified amount of justification A—for, example, that no proposition in D is conclusively justified or has the amount of justification necessary for knowledge.
EXTREME JUSTIFICATION SKEPTICISM about a domain of potential belief D is the view that no proposition P in D has any justification or that no proposition P is more probable, more reasonable, or more epistemically justified than any other, including –P. (Pyrrhonian skeptics were extreme justification skeptics.)
Pojman's focus is on knowledge skepticism. BonJour focuses on justification skepticism. Pojman says that modern skeptics (e.g., Descartes and Hume) are knowledge skeptics. This is a serious misrepresentation of many modern skeptics, including Hume. Many modern skeptics (including Hume) are extreme justification skeptics.
A GLOBAL SKEPTIC is a skeptic about everything (or almost everything). [Descartes raises global skeptical arguments, which he thinks he can refute, but there is general agreement that his reply fails for almost everything we think we know.]
A LOCAL SKEPTIC is a skeptic about some domains of inquiry but not others. [Hume was a local skeptic about many domains of inquiry.]
Examples of Hume's local skepticism:
(1) beliefs about cause and effect
(2) beliefs about external objects and theoretical entities (recall his objection to Locke's representationalism)
(3) beliefs about the future (induction)
(4) beliefs about the self
(5) moral beliefs.
The Problem of the Criterion
A question of priority:
(1) Which specific beliefs are justified?
Epistemological particularists give priority to the answer to #1.
(2) What are the criteria that must be satisfied for a belief to be justified?
Epistemological Generalists give priority to #2.
Responses to Skepticism
1. Descartes's Response
The Cartesian Circle
1a. BonJour's Cartesian Response
2. The Particularist's Response
3. The Contextualist's Response
4. The Coherentist's Response
5. The Externalist's Response
Nozick's Tracking the Truth Account of Knowledge or Dretske's Relevant Alternatives account of Knowledge.
Both deny that knowledge is closed under known entailment. That is, both deny:
Kp & K(p à q) à K(q)
Do I know that I am not a brain in a vat?
6. The Naturalist's Response
7. The Pragmatist's Response
8. Rorty's Rejection of Epistemology
The Crucial Presumption About Justification
That BonJour Shares With the Skeptic
The Crucial Presumption Of Justification Skepticism:
S is justified in believing that p ó S has a non-question-begging reason for believing that p is true (BonJour).
Because it is only linear reasoning that can technically be question-begging, the crucial presumption commits us to a linear conception of good reasoning. After exploring some of the implications of the crucial presumption, we will consider whether to give it up and, with it, the presumption that good reasoning is linear.
What follows from this presumption?
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.e., belief in necessary truths) and
(3) beliefs describing our current experience.
However, BonJour's move to allowing for fallible justification seems to make it inevitable that there are two kinds of skepticism that we must surrender to:
FIRST KIND OF SKEPTICISM TO WHICH WE MUST SURRENDER: Total skepticism about basic a priori justification. If apparent a priori insights can be false, then consider the possibility that there is an Evil Genius distorting all of them, so that they are all (or almost all) false. In such a case, what we take to be our a priori faculty would never (or rarely) gives us true beliefs. In the book In Defense of Pure Reason, BonJour acknowledges that in this case, none of our apparent a priori justified beliefs would actually be justified, though we would have no way of being able to tell. This leads him to acknowledge an externalist condition on a priori justification, which is roughly that our apparent a priori faculty actually be reliable (since it is not an infallible) source of belief in necessary truths.
If it seems implausible to you that all or almost all of our apparent a priori insights could be mistaken, note that there is a less extreme form of this skepticism about a priori justification that would be almost as devastating: Skepticism about inference to the best explanation. Consider the possibility that there is an Evil Genius who distorts our judgments of goodness of explanation, so that the explanations that we tend to think of as good ones are really terrible explanations. It seems clear that this sort of distortion of our a priori faculty is possible, because paranoid schizophrenics seem to differ from us in just this way: To them conspiracies always seem like the best explanation of everything. Because, for BonJour, almost all our beliefs that go beyond basic ones (including beliefs about the past, the future, the external world, other minds, and also the sciences) depend on inference to the best explanation, skepticism about inference to the best explanation undermines almost all of our beliefs that go beyond the basic ones.
SECOND KIND OF SKEPTICISM TO WHICH WE MUST SURRENDER: Total skepticism about basic empirical justification. Although BonJour does not discuss the problem, if our empirical basic beliefs are also fallible, a parallel problem arises for them. We must consider the possibility that they are all (or almost all) mistaken. By analogy with BonJour's discussion of a priori justification, we would expect that he would allow for this possibility and simply insist that in the case of such massive unreliability, none of our empirically basic beliefs would be justified. In such a case, what we take to be the empirical given would never give us true beliefs. None of our apparent empirically basic beliefs would actually be justified, though we would have no way of being able to tell. This would lead to an externalist condition on empirical justification, which is roughly that experience (the empirical given) actually be a reliable source of basic beliefs (since it is not infallible).
In what follows, we will assume that these two externalist conditions are satisfied. Though keep in mind that they represent two forms of skepticism to which we can do nothing but surrender.
In Chapter 8 of the text, BonJour identifies the third kind of skepticism to which we must surrender. 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?
It would seem that we would have to be justified in relying on our memory of the premises that are not currently in our mind.
Question #2: Are we justified in believing the results of reasoning of more than one step, when the premises are from one of the three categories above and each step of the reasoning is validated by a rational insight that if the premises are true the conclusion either must be or is probably true?
Consider reasoning that involves two steps. After the first step, we reach an intermediate conclusion that is then used as a premise in the second step of the reasoning. When we finish the second step are we justified in accepting the final conclusion? As a matter of fact, to carry out the reasoning, we must remember either the reasoning to the intermediate conclusion or the fact that we did reason to it.
These questions illustrate what BonJour calls the preservative role of memory in reasoning. To be justified in believing these memory beliefs, either memory would have to be a foundational source of basic beliefs about the past or we would have to be able to reason from foundational beliefs to the conclusion that memory beliefs are reliable.
BonJour acknowledges that it is very implausible to think that the content of current memory experience could be a foundational source of basic beliefs about the past. So BonJour rejects the first alternative. But the second alternative would clearly be question-begging, because the reasoning that established the reliability of memory would certainly be complex enough to require the use of memory in its preservative role.
On page 182 of the text, BonJour acknowledges that there is no choice but to surrender to skepticism about the preservative role of memory in reasoning. In his book, In Defense of Pure Reason, he adds a further externalist condition to his account, which is roughly that memory in its preservative role in reasoning must be reliable.
So THE THIRD FORM OF SKEPTICISM TO WHICH WE MUST SURRENDER is skepticism about the reliability of memory in its preservative role in reasoning.
What about the justification of other beliefs about the past based on memory?
Note that there are three kinds of beliefs that depend on memory. Consider my situation as I have the phenomenological experience of seeming to remember seeing a blue desk yesterday:
(1) Belief about an apparent memory experience: The belief that it seems to me that I had an experience of seeming to see a blue desk yesterday.
Belief (1) is a basic belief about my current experience. It is directly justified by my current experience, so there is no problem in justifying it.
(2) Belief about the past experience it is an apparent memory of: The belief that I had an experience of seeming to see a blue desk yesterday.
BonJour considers and rejects the idea that belief (2) might be a basic belief, directly justified by my current memory experience. This seems right. It is hard to see how my current experience could directly justify any proposition about the past.
So if I am justified in believing beliefs about past experience, I will have to reason to them from other beliefs. The only plausible way to reason to beliefs about the past from beliefs about my current memory would be to try to argue that the fact that those memory beliefs are generally true is the best explanation of why we have them. This is just the first of a number of inferences to the best explanation that BonJour hopes to use to show that, if the three external conditions identified above are satisfied, our beliefs about the past and future, the external world, other minds, and also science are justified.
BonJour's Anti-Skeptical Project for Epistemology
BonJour proposes that we set aside the three forms of skepticism that we have to surrender to, by simply adopting as external conditions on justification the assumption that they are mistaken. Then the Anti-Skeptical Project is: On the basis of our memory beliefs and the two kinds of foundational beliefs (a priori and empirical) we must construct a non-question-begging argument that our beliefs about the external world, the past and future, other minds, and also science are probably true.
An Outline of the Argument:
(1) Specification of the evidence: E = All of the basic a priori beliefs and basic empirical beliefs and all of our beliefs based directly on memory experiences (including remembering some propositions as being necessarily true).
(2) Specification of our justified beliefs about the external world (or about the past and future or other minds or science): B1, B2, . . . , Bn.
(3) In order to have any justification for believing any particular belief about the external world, Bi, we must be able to derive a priori the following proposition:
PROB(Bi/E) > 1/2 (i.e., > PROB(-Bi/E)).
This derivation will presumably begin with general a priori probabilities, from which the particular probabilities (PROB(Bi/E)) will be derived a priori.
BonJour's Anti-Skeptical Project
(1) No one has ever specified even a small proportion of their total evidence E.
(2) As a direct consequence of problem (1), no one has ever even formulated any of the crucial a priori probabilities, PROB(Bi/E).
(3) There is no general agreement among philosophers on any general a priori probabilities from which for any reasonable specification of evidence E and any interesting belief about the external world Bi (or about the past or future or about other minds or from science), it can be derived that PROB(Bi/E) > 1/2.
(4) Because of (3), the only reasonable hope for discovering general probabilities from which the relevant particular probabilities can be derived is to reason at least in part in a bottom-up direction from the particular probabilities to try to find general probabilities from which they could be derived. 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.
This is the FOURTH KIND OF SKEPTICISM TO WHICH SURRENDER SEEMS UNAVOIDABLE: Skepticism about the possibility of justifying beliefs about the external world (or the past and future or other minds or science) on the basis of BonJour's foundational beliefs and memory beliefs.
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.g., ordinary beliefs about the external world) are justified and some beliefs (e.g., biased Aryan history or astrological predictions) are not. 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. But if the subject is our shared conception of justification, then bottom-up reasoning could lead us to give up one or more of our presumptions about it, just as Gettier examples led most epistemologists to give up their presumption that K ó JTB.
Is justification linear or non-linear? What do you think it makes the most sense to believe?