Version 2.21, October 6, 2008
The subject of this course is what has come to be called "theory of knowledge" or "epistemology." The two names are interchangeable in common use. (A similar pair of terms for philosophical disciplines is 'theory of value' (or 'value theory') and the little-used 'axiology.') Until the nineteenth century, there had been no special term to indicate the study of knowledge as such, even though knowledge had been studied from the very beginning. The word "epistemology" was coined by James Ferrier in his 1856 book Institutes of Metaphysics. The root word 'episteme' in Greek means 'knowledge,' while the '-ology' suffix signifies, roughly, 'study of.' Compare terms such as 'biology' (study of life), 'geology' (study of the earth), etc. Shortly after Ferrier, Eduard Zeller in 1862 introduced the German word 'Erkenntnistheorie' in Ueber Aufgabe und Bedeutung der Erkenntnistheorie. This word is translated into English as "theory of knowledge."
All the great philosohers in the Western tradition (e.g. Plato, Aristotle, Descartes, Hume, and Kant) were deeply engaged in epistemology. In modern Anglo-American universities, theory of knowledge is considered to be one of the "core" sub-disciplines of philosophy. It is frequently linked to metaphysics, the general study of reality, as a component of the center of philosophy, "M & E" (metaphysics and epistemology). In our own numbering system in the UC Davis philosophy department, Metaphysics is Philosophy 101 and Theory of Knowledge is Philosophy 102. Virtually every philosophy department in the English-speaking world has at least one person who teaches and does research in theory of knowledge.
Each year, numerous articles and a fair number of books on the topic appear in print. Other pieces are posted on Web sites. Papers on the theory of knowledge are given at all meetings of the American Philosophical Assocation, as well as at many general philosophical conferences. There are frequent special conferences on the theory of knowledge, including a major conference offered every year at Rutgers University, which is one of the leading departments in the field. A Web log devoted to epistemology was established in 2004. Another blog hosted by Duncan Pritchard at the University of Sterling is centered on epistemic value.
There are many distinguishable projects that make up the study of knowledge. These projects overlap with one another in various ways, as we will see throughout the course. We will be concerned here with six projects which comprise the heartland of epistemology.
The Methodological Project
It seems that the study of knowledge ought to be undertaken in an orderly way, but there is widespread disagreement among epistemologists about how to study knowledge. Some of the disagreement is based on differences in their general approaches to philosophical investigation. We shall here call attention to several such differences.
Descriptive versus Normative Approaches
Many philosophers make a fundamental distinction between questions of fact and questions of value. One way of making this distinction is in terms of what is and what is permitted to be or what ought to be. Here is an example from ethics. It is a question of fact whether a person A has killed person B. But even if it is established that A killed B, there is a further question as to whether it was morally permissible or morally impermissible for A to have killed B. In questions of value, it is standard practice to invoke standards or norms by which these questions may be judged. The issue for epistemology is whether the study of knowledge is a purely descriptive discipline, a purely normative discipline, or a discipline with both descriptive and normative components.
It is possible to take any of the three positions. A purely descriptive approach would take it that the task of epistemology is to discover and explain the ways in which information is processed by those systems (living or mechanical) which are capable of processing information. To be sure, such processing of information is subject to rules by which the information is evaluated by the system which is processing it. In itself, this does not make epistemology a normative discipline, because the sole task of the purely descriptive epistemologist would be simply to describe the norms of the system which uses them.
A second position would be that the task of epistemology is solely to establish which set or sets of norms are adequate (or perhaps optimal) for knowledge. Potential standards for knowledge differ in how demanding they are. Historically, philosophers (such as Descartes) have set a very high bar for knowledge, requiring absolute certainty. In ordinary life, we tend to set lower standards. For example, it is common to allow that a person can gain knowledge solely on the basis of what someone else has told him or her. We can characterize the strength of standards in terms of how strong an epistemic position the knower must have in order to know. Then a purely normative approach to epistemology would be concerned with establishing how strong one's epistemic position must be in order to know, and how one might attain such a position. For example, one might hold that valid deductive reasoning preserves the strength of one's epistemic position.
At its most abstract level, a purely normative approach would consider rules that apply to any possible knowing being. If the norms are to govern a specific kind of being (for example, adult human beings), some description of the capacities of those beings would have to be given. Then the project would be to study the norms applying to that kind of being.
It seems that either of these two "pure" approaches would leave out much of interest to the student of knowledge. Even if we know how a system processes its information, we surely would wish to discover whether it is processing the information well. And even if we are able to set down a set of norms are appropriate to knowledge, we surely would want to find out whether and how they apply to the world. Historically, most work in epistemology has been of a mixed variety. Unfortunately, there has been little agreement as to the precise nature of the mix.
Here is an example of one such dispute. Some philosophers, such as Descartes, have held that human beings can determine by a process of self-inspection what their cognitive capacities are. They claim further that it is possible for humans to use purely internal resources to determine the proper standards for the use of these capacities, as well as whether those standards have been met. In that case, epistemology can be done "in the armchair," or (to use a more high-sounding expression), a priori. Others reject this approach, claiming that the correct description of the capacities of humans must be determined through "cognitive science," which is an empirical, interpersonal, approach to discovering the facts about knowers that are relative to their ability to know.
Particularism versus Methodism
A different kind of deep disagreement about how to do study knowledge has to do with the starting-point of the investigation. Probably the majority view these days is that we should take as a datum or starting-point that people have knowledge and then go on to discover what its characteristics are. This kind of investigation is suggestive of the methodology of the empirical sciences. But others think that we must begin with a prior conception of the characteristics knowledge has, and then go on to investigate whether or not we have any knowledge. Roderick Chisholm has called the first line of investigation "particularism" and the second "methodism." ("The Problem of the Criterion," The Aquinas Lecture, 1973, reprinted in Chisholm, The Foundations of Knowing, 1982.)
Chisholm recognized that it is not easy to see how this disagreement could be resolved in a principled way (that is, resolved other than by dogmatically asserting that one's own approach is the correct one). For how, he asked, can we identify items of knowledge unless we already have a prior conception of what knowledge is? This consideration seems to favor methodism. But we can ask as well how we can get a conception of what knowledge is if we have not already determined what items are to count as items of knowledge. Now particularism seems to have the advantage. Yet to motivate the choice of items that count as knowledge, one would seem to require a prior conception of what knowledge is. This takes us around again to methodism, and we seem to be on a "wheel."
A particularist might claim that there is a satisfactory way to pick out cases of knowledge without a prior conception. We can simply observe what people are willing to identify as cases of knowledge. This strategy avoids "the wheel," but it should be noted that it must deal with any variability in which cases are identified as knowledge by different people, or by the same person at different times. The methodist might claim that there is some external source for his conception of knowledge. For example, one might cite the ways in which philosophers have traditionally conceived of knowledge. But here again, any variability that might be found must be accounted for.
In the twentieth century, the study of language has played a much more important role in philosophy than it had before. This has led philosophers to investigate the meaning and use of "know" in language. There are several different ways in which this investigation can be undertaken. The most familiar way is to give an analysis of certain expressions containing the word 'know.' The analysis is supposed to express necessary and sufficient conditions for knowing. Generally, the conditions proposed by epistemologists do not contain the word 'know,' and so it is concluded that knowledge is "reducible" to something more fundamental.
The analytic approach, which will be discussed in detail in this course, has fallen out of favor in recent times. A different way of investigating 'know' is to try to discover the ways in which it is used by speakers of the language in various contexts. This approach has special appeal to philosophers of language, many of whom have "crossed over" to epistemology in trying to determine the conditions of the use of 'know.' This method of investigation is largely descriptive in nature, since it concerns how users of language actually behave. It may uncover linguistic rules that govern the use of the word, but it does not pronounce on the propriety of usage.
The original investigations into the way in which 'know' is used was carried out in the 1940s by J. L. Austin, under the influence of Ludwig Wittgenstein. Austin was concerned with self-attributions of knowledge, when a person utters sentences like, "I know that you will like this wine." According to Austin, making attributions of this kind is similar to making a promise. In uttering the words "I promise," one has created a new reality (so to speak), a commitment to do what one has promised. Similarly, when one utters the words "I know," one is giving one's word that what he has said to know is actually the case. The speaker is indicating that he may be held responsible if he turns out to be incorrect.
More recently, much attention has been devoted to the context of knowledge attribution. It has been pointed out that different speakers, armed with exactly the same information about a given person, are inclined to differ in their attributions or denials of knowledge. This is taken as a datum to be explained. The explanation for the difference is to be found in variability of epistemic standards based on the context of attribution or denial. It seems that certain contextual factors, such as the practical consequences of being wrong, affect the strength of the epistemic position we require for knowledge. As will be seen, there is a good deal of disagreement about which contexts are crucial in knowledge attribution and exactly what role the context plays.
The Analytic Project
Thus far, almost nothing has said about what knowledge is, except that it is something that meets some standards or other, or that it requires that the knower be in an epistemic position of some strength or other. Since the beginnings of epistemology in Plato, philosophers who think there is such a thing as knowledge have been inquiring into its nature. As will be seen, it is not easy to say what knowledge might be.
It is not even clear what one is doing in trying to determine what knowledge is. Most would say that the epistemologist is giving an "analysis" of knowledge. One way to think of analysis (going back to Leibniz in the eighteenth century) is that it begins with a concept and extracts the content of that concept. Another approach is to hold that knowledge is a property and the analysis is supposed to reveal under what circumstances the property is instantiated (that is, for something to have that property). In any case, an analysis gives a set of necessary and sufficient conditions for knowing. One must satisfy those conditions in order to know, and if one satisfies those conditions, then one does know.
It seems that all knowledge must be attributed to something that knows, which we will call an "epistemic subject." We will use the variable 'S' to stand for a possible knowing subject. What this subject might be is a matter of great controversy. Knowledge has been attributed to human beings, gods, animals, computers, and probably other things as well. Some epistemologists think that knowledge is confined to a relatively small class of beings, perhaps to mature, rational human beings. Others are willing to attribute knowledge to a broad class of beings.
There is pretty general agreement that any knowing subject must be capable of somehow representing reality. That is, knowledge is said to be knowledge of what is the case in the world. One way of expressing this is to say that knowing is "intentional," in that what is known is something that the knower "intends." Another way to put the point is that the knower's knowledge is supposed to be "about" what is the case in the world.
Just what it is that knowledge represents is somewhat controversial. The most common claim by epistemologists is that knowledge represents states of affairs, and that it does so through propositions. Thus, where 'p' is a variable standing for a proposition, it is common for epistemologists to try to give the conditions under which S knows that p. Under what conditions, for example, do I know that there is a ticking clock above my desk?
Other kinds of knowledge involve concrete things. I may be said to know my parents, my wife, my car, my golf course, etc. This kind of knowledge gets relatively little treatment by epistemologists. A further kind of knowledge is "knowing how," sometimes called "procedural knowledge." This kind of knowledge gets more attention than "knowing who" or "knowing what," but still not nearly as much as does "knowing that." We shall accordingly focus our attention primarily on the conditions (if any) under which in general S knows that p.
It will be helpful to have a compact way of representing attributions or denial of knowledge that p to a subject. To this end, we will use the letter 'K' to indicate knowledge. To represent that S knows that p, we shall place a subscripted 'S' after the 'K' and before the 'p.' Thus we have:
KSp.We may add a second subscript, 't,' to indicate that time at which S knows that p. Thus we will write:
KS,tp.Some epistemologists think that some contextual features of S's situation at t are also important to whether S knows that p. Since the time is a component of any context, we can replace the 't' with a 'c' and write:
KS,cpto indicate that S knows that p in context c. If C is a condition thought to be necessary for S to know that p, we may write:
KS,cp → CWe will now begin considering some widely-accepted necessary conditions for knowledge.
It is generally agreed that in order for any subject to know that p, it must be true that p, or the case that p. This necessary condition was endorsed by Plato, the first philosopher to investigate the conditions for knowing (see Plato's Theatetus. But even this condition can be controversial, particularly because there is substantial disagreement about what it is for a proposition to be true. Others dispute the condition itself. These philosophers generally tie knowledge to social practice and consider it primarily in terms of being "authoritative" rather than "true."
We can symbolize the truth-condition in the following way:
KS,cp → p.We have used 'p' rather than a symbolization of 'it is true that p' because the latter seems to imply the former. If it is true that Tiger Woods is a famous golfer, then Tiger Woods is a famous golfer.
A second widely-accepted condition for knowledge is that S believe or accept that p. Broadly speaking, the idea is that for S to have knowledge that p, S must in some way be definitely committed to the truth of p. Yet despite the widespread agreement that there must be some kind of strong commitment for there to be knowledge, there is a good deal of disagreement about the exact nature of the commitment that is required for knowledge. One area of dispute concerns the kind of cognitive activity that is required for knowledge. Some hold that one must be committed intellectually to the truth of p, while others hold that that one need only be committed in a way that disposes him to act as if p were true. A person talking on a mobile phone while driving might be too distracted to make an intellectual commitment to there being a car in front of him in his lane, yet is in some way committed to its being there, as evidenced by the fact that he maintains a uniform spacing behind that car.
The symbolization of the belief condition can be carried out the same way as with knowledge. We will use the symbol 'B' to indicate belief, and we will index this symbol with a reference to the epistemic subject and the context of belief.
KS,cp → BS,cp.
Although there is pretty broad consensus that S's knowing that p requires that p be true and that S believe that p, further conditions in the analysis are quite controversial. It is generally accepted that knowledge is more than mere true belief. A belief that is formed on the basis of third-hand gossip might be true, but it seems that this source of information does not put the subject in a very strong epistemic position. In general, we can say that for S to know that p, S's epistemic position with respect to p must be strong enough, according to some standard of strength. Of course, the difficulty is to specify what gives strength to one's epistemic position, and to specify how strong that epistemic position must be in order to amount to knowledge.
We need a term to stand for the degree of strength of epistemic position that enables us to distinguish knowledge from true belief. Alvin Plantinga has proposed the term 'warrant.' Here is how Plantinga describes warrant:
Initially then, and to a first approximation, warrant is a normative, possibly complex quantity that comes in degrees, enough of which is what distinguishes knowledge from mere true belief (Warrant: The Current Debate, 1993, p. 4).We can use this notion to say that a necessary condition for S's knowing that p is that S is warranted to a sufficient degree. We will let 'W' stand for this notion of sufficient warrant. Then we can write:
KS,cp → BS,cp.
What is highly controversial is the question of what is relevant to the strength of S's epistemic position and what the standard of strength ought to be. Probably the most common way of understanding sufficient warrant is that S's belief that p be "justified." Sometimes this is understood in terms of S's having "good reasons" or "good evidence" for believing that p is true. Not surprisingly, there is little agreement about exactly what it takes for a belief to be justified. Much of the literature of epistemology is centered on this normative issue, which will be the topic of much discussion in what follows.
Many philosophers think that justification or the having of reasons is not necessary for knowledge. For the most part, these epistemologists regard justification as too narrow a condition to capture all types of knowledge. Some have proposed that the warrant condition might or might not include justification. A true belief might be sufficiently warranted and amount to knowledge without "reasons" or "evidence" being involved when something else gets S into a position to know.
One of the central issues in epistemology today is whether or not knowledge requires reasons, or the conscious awareness of reasons, for the truth of what is known. Those who impose this kind of requirement are known as "internalists." "Externalists," on the other hand, impose no such requirement, though there is considerable disagreement about what other requirement should take its place. Two leading candidates are reliability in the process of forming the belief that p (reliabilism) and the exercise of "virtuous" (or excellent) cognitive faculties (virtue epistemology).
Our use of the term 'warrant' is vague enough to accommodate internalism or externalism. The term was introduced by Plantinga as a way of being non-committal about what exactly is required for a subject to be in a strong enough epistemic position for knowledge. Putting the truth, belief, and warrant conditions together, we arrive at what has been called the "traditional" analysis of knowledge. We will use the symbol '∧' to indicate the conjunction of conditions.
KS,cp ↔ (p ∧ BS,cp ∧ WS,cp).S knows that p (in context c) if and only if p, S believes that p (in context c), and S is sufficiently warranted (in context c) in believing that p. Note that one need not relativize knowledge to context. If one takes knowledge to be "invariant," then the context index may be ignored.
There is a problem with the "traditional analysis" that is especially troublesome for internalists. On some accounts of sufficient warrant, it is possible for one to have a sufficiently warranted true belief by accident. That is, one may form the true belief that p despite being in a very weak epistemic position. Suppose I flip a coin, and you spontaneously call "heads." The coin turns up heads. Did you know that it would, or were you just lucky to have made the right call? It seems that your epistemic position was too weak for me to say that you knew it would. It seems to be a condition on knowledge that if S is to know that p, the truth of S's belief that p not be accidental.
One way in which accidentally true belief that p may arise is when a belief that p is justified in a way that does not reflect the reason that p is true. In a short paper published in 1963 by Edmund Gettier ("Is Knowledge Justified True Belief?"). Gettier offered two hypothetical cases in which a justified true belief apparently fails to be knowledge, because p is true because of circumstances that are not taken into account in the justification. (One example is reproduced here.) The relevant cases have come to be known as "Gettier cases."
There are two standard ways to try to deal with Gettier cases in the analysis of knowledge. One way, which seems especially appropriate for externalists, is to build a "no accident" condition into the account of warrant. Then the form of the analysis would not change. For example, Alvin Goldman's initial response to the Gettier cases was to propose an analysis according to which S's belief that p must be caused in an "appropriate" way by the fact that p ("A Causal Theory of Knowing," Journal of Philosophy 64 (1967), pp. 357-372). The requirement of "appropriateness" would be spelled out so as to exclude accidental true belief from counting as knowledge.
A second approach is favored by internalists. It appears that unless only absolute certainty is to count as sufficient warrant, there is no way for an epistemic subject to rule out "from the inside" the possibility that his belief is accidentally true. As a result, it is common for internalists to require a fourth condition of knowledge--one which excludes the accidental belief that p. If we use 'NB' to signify that a belief is not accidentally true, we can specify this kind of condition:
KS,cp → NBS,cp.Then the complete analysis looks like this:
KS,cp ↔ (p ∧ BS,cp ∧ WS,cp ∧ NBS,cp).As will be seen, it is difficult to find a satisfactory way to deal with accidentally true belief.
Trying to discover the standards of knowledge is one of the most important projects in epistemology. It may reasonably be called the "normative" project because the word 'norm' is used much as is the word 'standard,' and the word 'normative' is used in areas of philosophy, such as ethics, when standards are the subject of study.
As has been stated, the standard for S's knowing that p can be understood abstractly in terms of the strength of S's epistemic position with respect to p. Whether S's epistemic position is strong enough is determined by whether S has satisfied the requisite norms. The choice of a set of norms depends on how strong it is thought S's epistemic position must be, so we will discuss this question first.
The traditional standard is that S be in the optimal epistemic position. In order to know that p, S's epistemic position with respect to p must be so strong that S could not go wrong in believing that p. This view is known as "infallibilism." The contrary view, "fallibilism," allows that S's epistemic position may be sub-optimal without excluding the possibility of S's knowing that p. Virtually all epistemologists today are fallibilists. Yet within fallibilism there is tremendous scope for disagreement, since there are myriad ways in which a subject's epistemic position may fall short of perfection.
In order to understand the nature of the norms governing knowledge ("epistemic" norms), it may be useful to compare them to ethical norms purporting to apply to human action. In one of their applications, ethical norms are the basis for judgments of the following kind:
Correlatively, we often make statements of the following types:
One question that arises immediately is whether the kind of "rightness" and "goodness" that are relevant to knowledge are at least partly ethical in character, or whether there is a special kind of epistemic rightness and goodness which has no moral overtones. (Alvin Plantinga has termed the conception of epistemic norms in terms of moral duty a "deontological" approach.) While most epistemologists do not understand epistemic norms in a way that is explcitly deontological, others do. William K. Clifford once stated that "it is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence" ("The Ethics of Belief," 1887). If the epistemologist thinks that there is some element of "rightness" or "goodness" involved with ethical standards, he must then try to discover the specific standards that would determine whether believing, reasoning, etc. are "right" or "good" for a subject S at a time.
Let us now leave aside the analogy with ethics and turn to the norms themselves. We must first distinguish between the basic norms governing knowledge and norms governing the selection of norms governing knowledge. Most of the investigation in epistemology is directed toward the lower-level norms that are said to govern whether one knows or is ignorant. (See especially the work of John Pollock on this subject.) However, there is debate about how to choose epistemic norms, as with the question of whether epistemic norms are tied to morality. Another dispute involves whether the choice of norms can be justified, or whether, as Pollock claims, all we can do is describe the epistemic norms we in fact use.
The norms governing knowledge are generally divided into two types, according to the complexity of the cases to which they apply. We may restrict our attention to an individual piece of information about a state of affairs (as expressed through the proposition that p), or we may consider the relation between proposition p and a group of propositions that "support" it.
The norms governing the relation between a proposition and a group of propositions generally fall under the heading of "logic." (This is not to imply that one must engage in logical reasoning in order for the support relation to exist. Some epistemologists think that the kind of support needed for knowledge requires explicit reasoning, and others do not.) So a proposition p might meet some standard for knowledge if it follows logically from some other propositions. These other propositions may get their standing by following logically from some further propositions. But, to re-phrase a contention Aristotle made in his Posterior Analytics, an infinite regress of logical connections of support cannot put a subject in a strong enough epistemic position.
This consideration led Aristotle and many others to hold that some propositions meet the standards of knowledge by themselves, which means that there are standards which apply to individual propositions taken by themselves. If a subject has knowledge in this way, such knowledge is typically called "basic." Some epistemologists think that what provides support for an individual proposition or set of propositions is not itself propositional. It might, for example, be a psychological state of S. The claim that there is something which supports all (other) knowledge is known in the literature as "foundationalism." There is much debate about how foundationalism should be fleshed out. For those who think the foundation is propositional, there is the question as to whether foundational propositions are justified or not? If they are justified, then do the propositions somehow justify themselves, or are justified in some other way?
We will say that a person gaining basic knowledge by satisfying those standards has knowledge by "intuition." There are two very different kinds of intuitive knowledge investigated in epistemology. One kind deals with abstract propositions, such as propositions about numbers or geometrical figures, or about truths of logic. The second kind deals with concrete propositions about existing states of affairs. For example, it is commonly held that people have intuitive knowledge of their being in intense pain. Whether there is intuitive knowledge at all, and if so what norms apply to it, is controversial, and we will be looking into the controversy later in the course.
Turning to the support relation, we find that the most basic division among standards (or rules) of logic is between deductive and non-deductive rules. A deductive rule is such that if each member of the set of initial propositions (premises) is true, the proposition they support (the conclusion) must also be true as well. This standard of "deductive validity" is considered by most to be as good a logical standard as there can be, in the sense that the conclusion cannot be supported any better. Drawing a deductively valid conclusion from one's premises leaves one's epistemic position with respect to the conclusion no weaker than one's epistemic position relative to the premises.
Some non-deductive rules of logic are called "inductive." Such rules begin with particular propositions and move to more general ones. A famous inductive generalization mentioned by David Hume is from the premise that the sun has in the past always "risen" in the morning to the conclusion that the sun always rises in the morning. The most prominent kind of inductive generalization is the kind made in statistics, where information from relatively small samples is generalized to larger populations. Inductive inference provides less support than does deductive inference, since, as Hume pointed out, there is always the possibility that the conclusion will deviate from even complete uniformity in the premises.
There are well-studied and widely accepted formalizations of rules for deductive and inductive inferences: formal deductive logic and the probability calculus, respectively. These formalized systems are generally taken to be very useful in formulating our epistemic norms.
A second class of non-deductive rules was called by C. S. Peirce "abductive." We more typically refer to them as "explanatory" rules. Most typically, we take a proposition to be well-supported by other propositions because it provides an explanation for them. For example, someone might think that the proposition that global warming is occurring now is supported because it explains various unusual weather patterns, as well as the breakup of the polar ice caps. Often we take a proposition to be supported because it is explained by something else. I might take a loud bang to be a car backfiring (and not gunfire) because an old car is passing nearby, in the direction of the sound. Explanatory rules turn out in practice to be very complicated, as will be seen later in the course.
One factor that is important in accounts of explanatory rules is "coherence," the way in which a proposition "fits" with other propositions. Some epistemologists have tried to lay down rules of coherence whose satisfication would be at least a partial standard for knowledge. We shall have more to say about coherence in the rest of the course.
We can distinguish the project of analyzing knowledge from the project of describing it. In trying to describe knowledge, we look at what processes actually take place so as to produce a state of knowing. The project, therefore, might also be called the "genetic" project, but since using that name risks a confusion with the science of genetics, I have opted to call the project "descriptive."
The most fundamental dispute among epistemologists over the description of knowledge is over the question of the role of conscious awareness. Internalists generally think that knowledge requires having reasons for one's belief. The descriptive task for these epistemologists is to show which reasoning processes we use, and how we obtain the premises used in the reasoning processes.
One area of interest for internalists is the possibility of knowledge a priori, that is, knowledge that is gained independently of sense-experience. The interesting descriptive task is to show what cognitive mechanism is capable of producing knowledge a priori (if any) and what kinds of a priori knowledge it can generate.
Externalists allow that there can be knowledge in the absence of having reasons. What matters is how the subject comes to believe that p. Clearly, the descriptive project, with its focus on how knowledge is produced, is central to externalist epistemology.
Some epistemologists are known as "naturalists." For these philosophers, it is essential to understand the subjects of knowledge as beings enmeshed in the natural world. If knowledge is a natural state, then it may be subject to investigation by natural science. The view that knowledge is to be understood entirely scientifically presents a problem, however, in that science itself is supposed to be the paradigm of knowledge. Whether we actually have scientific knowledge would have to be investigated scientifically, i.e., by its own standard.
Another group of epistemologists describes knowledge largely in social terms. What is important in the descriptions by the social epistemologists is the way in which belief arises as the outcome of social interaction. An important social group is natural scientists, and much work has been done to describe the ways in which the social practice of science influences its claims to knowledge. It should be added that a social epistemologist might well wish to investigate social epistemic norms, as well as describing social conditions under which knowledge arises.
The last project to be considered in these notes, that of "validation," is perhaps the most difficult and frustrating of all. Here the question is a simple one: given whatever it is that we think knowledge is, do we have any of that? An epistemological skeptic is a philosopher who denies or at least questions whether we have the knowledge we think we do. Since the middle of the seventeenth century, and following Descartes, many people have held that settling the question of validation is the central problem of epistemology.
The problem of validation has many dimensions. One of the most difficult problems is to show why it is that the epistemic norms that we have in place are sufficient for knowledge. A notorious problem along these lines was posed in the eighteenth century by David Hume. He advanced an argument according to which there is no way to validate the use of inductive reasoning, which throws its status as an epistemic norm into question. This argument is a staple of philosophy classes, partly because it has proved so difficult to overcome.
Another famous issue was raised originally by Descartes. He described some extreme hypotheses, in which our beliefs are incorrect in a way that we cannot detect. For example, it may be that we are disembodied spirits who are deceived by a powerful demon, who produces in our minds experiences just like those we would have if a world of physical bodies were responsible for our experiences.
Given that I cannot rule out the possibility that I am defective in just this way, how can I be said to have knowledge? In reply, many epistemologists follow the lead of the eighteenth century contemporary of Hume, Thomas Reid. Reid thought that any philosophical theory that would lead to the questioning of our common-sense beliefs should be rejected just because it encourages us to doubt what we would otherwise believe common-sensically. The early twentieth-century epistemologist G. E. Moore presented the same kind of argument. These philosophers of "common sense" are particularists who think that beginning with fixed epistemic norms threatens a skeptical result that is intolerable.
Many people, however, are impressed by the skeptical hypotheses and are inclined, when thinking about them, to doubt that they have the knowledge they ordinarily think they have. They become temporary skeptics. Those who advance a contextualist account of knowledge attribution have a way of describing what happens when a skeptical hypothesis is considered. The standard for knowledge is raised, temporarily, to the point where it is not satisfied. Thus they can, unlike Reid and Moore, acknowledge the force of skeptcial hypotheses while allowing that there is knowledge in most contexts.
Skepticism is generally thought to be more of a problem for internalists than for externalists. Recall that the basic requirement of internalism is that one must be at least potentially aware of having reasons which adequately support those beliefs that need support. For the internalist, if S cannot determine that his reasons are adequate, then S lacks knowledge.
The externalist, on the other hand, does not require awareness of the adequacy of one's warrant. As long some external condition, such as the (for the reliabilist) reliability of the belief-forming process, is met, one can have knowledge. The internalist counters that even if the externalist condition is satisfied, one might be left wondering whether one knows or not.
Much of the discussion of validation concerns ordinary perceptual belief. This did not concern the ancient Greek skeptics, who did not call into question beliefs about "the appearances." They were concerned with beliefs which go beyond the appearances, such as beliefs about the past or the future, beliefs about distant or minute objects, or beliefs about what an object that appears in a certain way really is. Their skepticism would also extend to beliefs which are part of broad theories about the makeup of the natural world, and especially beliefs about anything said to be supernatural.
The problem in all these cases is that we seem never to have enough evidence to elevate our belief to the level of knowledge. Moreover, there is frequently disagreement about such matters--disagreement that we lack the means to settle. Even if we assume that some are right and some are wrong, how can we determine who it is?
It is possible to apply this last skeptical consideration to the theory of knowledge itself. Virtually every position that has been described in this introduction is subject to controversy, sometimes to intense controversy, among the students of knowledge. In many cases, the parties seem to have exhausted the arguments for their positions, yet without persuading their opponents. Each new account of knowledge is promoted as more satisfactory than its rivals, but nothing even approaching a consensus has been reached by epistemologists. This holds more generally in philosophy. There simply is no agreement on substantive philosophical issues that looks anything like the general agreement on, say, principles of natural science.
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