The Competitiveness of Nations
in a Global Knowledge-Based Economy
January 2003
Avrum Stroll
A.P. Martinich
Epistemology
Encyclopedia Britannica,
Britannica 2003 Ultimate Reference Suite
Index
|
Web Page 1
“Our knowledge of the external
world” Relation of epistemology to other branches of Occurrent versus dispositional conceptions
A priori versus a posteriori
knowledge
Necessary versus contingent
propositions
Analytic versus synthetic
propositions
Tautological versus significant
propositions
Logical versus factual
propositions Knowledge by acquaintance and knowledge |
Medieval philosophy St. Anselm of St. Thomas Aquinas John Duns Scotus William of Ockham From scientific theology to secular
science Modern philosophy Faith and reason Impact of modern science on
epistemology René Descartes John Locke George Berkeley David Hume Kinds of perceptions Cause and effect Substance Relations of ideas and matters of
fact Skepticism Immanuel Kant G.F.W. Hegel Contemporary philosophy Continental philosophy Analytic philosophy Commonsense philosophy, logical positivism, and naturalized epistemology Perception and knowledge Realism Phenomenalism Philosophy of mind and epistemology |
the study of the nature, origin, and limits of human knowledge. The name is derived from the Greek epistAmA (“knowledge”) and logos (“reason”), and accordingly the field is sometimes referred to as the theory of knowledge. Epistemology has had a long history, spanning the time from the pre-Socratic Greeks to the present. Along with metaphysics, logic, and ethics, it is one of the four main fields of philosophy, and nearly every great philosopher has contributed to the literature on the topic.
Why should there be such a subject as epistemology? Aristotle provided the answer when he said that philosophy begins in wonder, in a kind of puzzlement about things. Nearly all human beings wish to comprehend the world they live in, a world that includes the individual as well as other persons, and most people construct hypotheses of varying degrees of sophistication to help them make sense of that world. No conjectures would be necessary if the world were simple; but its features and events defy easy explanation. The ordinary person is likely to give up somewhere in the process of trying to develop a coherent account of things and to rest content with whatever degree of understanding he has managed to achieve.
Philosophers, in contrast, are struck by, even obsessed by, matters that are not immediately comprehensible. Philosophers are, of course, ordinary persons in all respects except perhaps one. They aim to construct theories about the world and its inhabitants that are consistent, synoptic, true to the facts and that possess explanatory power. They thus carry the process of inquiry further than people generally tend to do, and this is what is meant by saying that they have developed a philosophy about these matters. Epistemologists, in particular, are philosophers whose theories deal with puzzles about the nature, scope, and limits of human knowledge.
Like ordinary persons, epistemologists usually start from the assumption that they have plenty of knowledge about the world and its multifarious features. Yet, as they reflect upon what is presumably known, epistemologists begin to discover that commonly accepted convictions are less secure than originally assumed and that many of man’s firmest beliefs are dubious or possibly even chimerical. Such doubts and hesitations are caused by anomalous features of the world that most people notice but tend to minimize or ignore. Epistemologists notice these things too, but, in wondering about them, they come to realize that they provide profound challenges to the knowledge claims that most individuals blithely and unreflectingly accept as true.
What then are these puzzling issues? While there is a vast array of such anomalies and perplexities, which will be discussed below in the section on the history of epistemology, two of these issues will be briefly described in order to illustrate why such difficulties call into question common claims to have knowledge about the world.
“Our knowledge of the external
world”
Most people have noticed that vision can play tricks on them. A straight stick put in water looks bent to them, but they know it is not; railroad tracks are seen to be converging in the distance, yet one knows that they are not; the wheels of wagons on a movie screen appear to be going backward, but one knows that they are not; and the pages of English-language books reflected in mirrors cannot be read from left to right, yet one knows that they were printed to be read that way. Each of these phenomena is thus misleading in some way. If human beings were to accept the world as being exactly as it looks, they would be mistaken about how things really are. They would think the stick in water really to be bent, the railway tracks really to be convergent, and the writing on pages really to be reversed.
These are visual anomalies, and they produce the sorts of epistemological disquietudes referred to above. Though they may seem to the ordinary person to be simple problems, not worth serious notice, for those who ponder them they pose difficult questions. For instance, human beings claim to know that the stick is not really bent and the tracks not really convergent. But how do they know that these things are so?
Suppose one says that this is known because, when the stick is removed from the water, one can see that it is not bent. But does seeing a straight stick out of water provide a good reason for thinking that it is not bent when seen in water? How does one know that, when the stick is put into the water, it does not bend? Suppose one says that the tracks do not really converge because the train passes over them at that point. How does one know that the wheels on the train do not happen to converge at that point? What justifies opposing some beliefs to others, especially when all of them are based upon what is seen? One sees that the stick in water is bent and also that the stick out of the water is not bent. Why is the stick declared really to be straight; why in effect is priority given to one perception over another?
One possible response to these queries is that vision is not sufficient to give knowledge of how things are. One needs to correct vision in some other way in order to arrive at the judgment that the stick is really straight and not bent. Suppose a person asserts that his reason for believing the stick in water is not bent is that he can feel it with his hands to be straight when it is in the water. Feeling or touching is a mode of sense perception, although different from vision. What, however, justifies accepting one mode of perception as more accurate than another? After all, there are good reasons for believing that the tactile sense gives rise to misperception in just the way that vision does. If a person chills one hand and warms the other, for example, and inserts both into a tub of water having a uniform medium temperature, the same water will feel warm to the cold hand and cold to the warm hand. Thus, the tactile sense cannot be trusted either and surely cannot by itself be counted on to resolve these difficulties.
Another possible response is that no mode of perception is sufficient to guarantee that one can discover how things are. Thus, it might be affirmed that one needs to correct all modes of perception by some other form of awareness in order to arrive at the judgment, say, that the stick is really straight. Perhaps that other way is the use of reason. But why should reason be accepted as infallible? It also suffers from various liabilities, such as forgetting, misestimating, or jumping to conclusions. And why should one trust reason if its conclusions run counter to those gained through perception, since it is obvious that much of what is known about the world derives from perception?
Clearly there is a network of difficulties here, and one will have to think hard in order to arrive at a clear and defensible explanation of the apparently simple claim that the stick is really straight. A person who accepts the challenge will, in effect, be developing a theory for grappling with the famous problem called “our knowledge of the external world.” That problem turns on two issues, namely, whether there is a reality that exists independently of the individual’s perception of it - in other words, if the evidence one has for the existence of anything is what one perceives, how can one know that anything exists unperceived? - and, second, how one can know what anything is really like, if the perceptual evidence one has is conflicting.
The second problem also involves seeing but in a somewhat unusual way. It deals with that which one cannot see, namely the mind of another. Suppose a woman is scheduled to have an operation on her right knee and her surgeon tells her that when she wakes up she will feel a sharp pain in her knee. When she wakes up, she does feel the pain the surgeon alluded to. He can hear her groaning and see certain contortions on her face. But he cannot feel what she is feeling. There is thus a sense in which he cannot know what she knows. What he claims to know, he knows because of what others who have undergone operations tell him they have experienced. But, unless he has had a similar operation, he cannot know what it is that she feels.
Indeed, the situation is still more complicated; for, even if the doctor has had such a surgical intervention, he cannot know that what he is feeling after his operation is exactly the same sensation that the woman is feeling. Because each person’s sensation is private, the surgeon cannot really know that what the woman is describing as a pain and what he is describing as a pain are really the same thing. For all he knows, she could be referring to a sensation that is wholly different from the one to which he is alluding.
In short, though another person can perceive the physical manifestations the woman exhibits, such as facial grimaces and various sorts of behaviour, it seems that only she can have knowledge of the contents of her mind. If this assessment of the situation is correct, it follows that it is impossible for one person to know what is going on in another person’s mind. One can conjecture that a person is experiencing a certain sensation, but one cannot, in a strict sense of the term, know it to be the case.
If this analysis is correct, one can conclude that each human being is inevitably and even in principle cut off from having knowledge of the mind of another. Most people, conditioned by the great advances of modern technology, believe that in principle there is nothing in the world of fact about which science cannot obtain knowledge. But the “other-minds problem” suggests the contrary - namely, that there is a whole domain of private human experience that is resistant to any sort of external inquiry. Thus, one is faced with a profound puzzle, one of whose implications is that there can never be a science of the human mind.
These two problems resemble each other in certain ways and differ in others, but both have important implications for epistemology.
First, as the divergent perceptions about the stick indicate, things cannot just be as they appear to be. People believe that the stick which looks bent when it is in the water is really straight, and they also believe that the stick which looks straight when it is out of the water is really straight. But, if the belief that the stick in water is really straight is correct, then it follows that the perception human beings have when they see the stick in water cannot be correct. That particular perception is misleading with respect to the real shape of the stick. Hence, one has to conclude that things are not always as they appear to be.
It is possible to derive a similar conclusion with respect to the mind of another. A person can exhibit all the signs of being in pain, but he may not be. He may be pretending. On the basis of what can be observed, it cannot be known with certitude that he is or that he is not in pain. The way he appears to be may be misleading with respect to the way he actually is. Once again vision can be misleading.
Both problems thus force one to distinguish between the way things appear and the way they really are. This is the famous philosophical distinction between appearance and reality. But, once that distinction is drawn, profound difficulties arise about how to distinguish reality from mere appearance. As will be shown, innumerable theories have been presented by philosophers attempting to answer this question since time immemorial.
Second, there is the question of what is meant by “knowledge.” People claim to know that the stick is really straight even when it is half-submerged in water. But, as indicated earlier, if this claim is correct, then knowledge cannot simply be identical with perception. For whatever theory about the nature of knowledge one develops, the theory cannot have as a consequence that knowing something to be the case can sometimes be mistaken or misleading.
Third, even if knowledge is not simply to be identified with perception, there nevertheless must be some important relationship between knowledge and perception. After all, how could one know that the stick is really straight unless under some conditions it looked straight? And sometimes a person who is in pain exhibits that pain by his behaviour; thus there are conditions that genuinely involve the behaviour of pain. But what are those conditions? It seems evident that the knowledge that a stick is straight or that one is in great pain must come from what is seen in certain circumstances: perception must somehow be a fundamental element in the knowledge human beings have. It is evident that one needs a theory to explain what the relationship is - and a theory of this sort, as the history of the subject all too well indicates, is extraordinarily difficult to develop.
The two problems also differ in certain respects. The problem of man’s knowledge of the external world raises a unique difficulty that some of the best philosophical minds of the 20th century (among them, Bertrand Russell, H.H. Price, C.D. Broad, and G.E. Moore) spent their careers trying to solve. The perplexity arises with respect to the status of the entity one sees when one sees a bent stick in water. In such a case, there exists an entity - a bent stick in water - that one perceives and that appears to be exactly where the genuinely straight stick is. But clearly it cannot be; for the entity that exists exactly where the straight stick is is the stick itself, an entity that is not bent. Thus, the question arises as to what kind of a thing this bent-stick-in-water is and where it exists.
The responses to these questions have been innumerable, and nearly all of them raise further difficulties. Some theorists have denied that what one sees in such a case is an existent entity at all but have found it difficult to explain why one seems to see such an entity. Still others have suggested that the image seen in such a case is in one’s mind and not really in space. But then what is it for something to be in one’s mind, where in the mind is it, and why, if it is in the mind, does it appear to be “out there,” in space where the stick is? And above all, how does one decide these questions? The various questions posed above only suggest the vast network of difficulties, and in order to straighten out its tangles it becomes indispensable to develop theories.
Index
Relation of
epistemology to other branches of philosophy
Philosophy viewed in the broadest possible terms divides into many branches: metaphysics, ethics, aesthetics, logic, philosophy of language, philosophy of mind, philosophy of science, and a gamut of others. Each of these disciplines has its special subject matter: for metaphysics it is the ultimate nature of the world; for ethics, the nature of the good life and how people ideally ought to comport themselves in their relations with others; and for philosophy of science, the methodology and results of scientific activity. Each of these disciplines attempts to arrive at a systematic understanding of the issues that arise in its particular domain. The word systematic is important in this connection, referring, as explained earlier, to the construction of sets of principles or theories that are broad-ranging, consistent, and rationally defensible. In effect, such theories can be regarded as sets of complex claims about the various matters that are under consideration.
Epistemology stands in a close and special relationship to each of these disciplines. Though the various divisions of philosophy differ in their subject matter and often in the approaches taken by philosophers to their characteristic questions, they have one feature in common: the desire to arrive at the truth about that with which they are concerned - say, about the fundamental ingredients of the world or about the nature of the good life for man. If no such claims were asserted, there would be no need for epistemology. But, once theses have been advanced, positions staked out, and theories proposed, the characteristic questions of epistemology inexorably follow. How can one know that any such claim is true? What is the evidence in favour of (or against) it? Can the claim be proven? Virtually all of the branches of philosophy thus give rise to epistemological ponderings.
These ponderings may be described as first-order queries. They in turn inevitably generate others that are, as it were, second-order queries, and which are equally or more troubling. What is it to know something? What counts as evidence for or against a particular theory? What is meant by a proof? Or even, as the Greek Skeptics asked, is human knowledge possible at all, or is human access to the world such that no knowledge and no certitude about it is possible? The answers to these second-order questions also require the construction of theories, and in this respect epistemology is no different from the other branches of philosophy. One can thus define or characterize epistemology as that branch of philosophy which is dedicated to the resolution of such first- and second-order queries.
Index
As indicated above, one of the basic questions of epistemology concerns the nature of knowledge. Philosophers normally interpret this query as a conceptual question, i.e., as an issue about a certain conception or idea or notion called knowledge. The question raises a perplexing methodological issue, namely, how does one go about investigating such conceptual questions? It is frequently assumed, though the matter is controversial, that one can determine what knowledge is if one can understand what the word “knowledge” means, that is, what notion or concept the word “knowledge” expresses or embodies.
Philosophers who proceed in this way draw a distinction between a word and its meaning, and a meaning is generally considered to be the concept which that particular word has or expresses. It is usually further assumed that though concepts are not identical with words, that is, with linguistic expressions, language is the medium in which the meaning of such concepts is displayed or expressed.
The investigation into the nature of knowledge often begins in a similar fashion with the study of the use of the word “knowledge” and of certain cognate expressions and phrases found in everyday language. A survey of such locutions reveals important differences in their uses: one finds such expressions as “know him,” “know that,” “know how,” “know where,” “know why,” or “know whether.” These differences have been explored in detail, especially in the 20th century. The expression “know x,” where “x” can be replaced by a proper name, as in “I know Jones” or “He knows Rome,” has been taken by some philosophers, notably Bertrand Russell (1872–1970), to be a case of knowledge by acquaintance. Russell thought its characteristic use was to express the kind of knowledge one has when one has first-hand familiarity with a certain object, person, or place. Thus, one could not properly say in the 20th century, “I know Julius Caesar,” since this would imply that one had met or was directly acquainted with a person who had died some 2,000 years ago. This sense or use of “know” becomes important in the theory of perception and in sense-data theory, since some philosophers, such as Russell and G.E. Moore (1873 -1958), have held that one’s awareness of a sense-datum (a notion to be discussed later) is a case of direct acquaintance, whereas one’s acquaintance with a physical object, such as a human hand, is not.
The phrases “know that” and “know how” have also played fundamental roles in the theory of knowledge. The British philosopher Gilbert Ryle (1900-76), for instance, argued that “know how” is normally used to refer to a kind of skill that a person has, such as knowing how to swim. One could have such knowledge without being able to explain to another what it is that one knows in such a case, that is, without being able to convey to another the knowledge required for that person to develop the same skill. “Know that,” in contrast, does not seem to denote the possession of a skill or aptitude but rather the possession of specific pieces of information, and the person who has knowledge of this sort can generally convey it to others. To know that the Concordat of Worms was signed in the year 1122 would be an example of this sort of knowledge. Ryle has argued that, given these differences, some cases of knowing how cannot be reduced to cases of knowing that and, accordingly, that the kinds of knowledge expressed by these phrases are independent of one another.
In general, the philosophical tradition from the Greeks to the present has focused on the kind of knowledge expressed when it is said that someone knows that such and such is the case, e.g., that A knows that snow is white. This sort of knowledge, called propositional knowledge, raises the classical epistemological questions about the truth or falsity of the asserted claim, the evidence for it, and a host of other problems. Among them is the much debated issue of what kind of thing is known when one knows that p, i.e., what counts as a substitution instance of p. The list of such candidates includes beliefs, propositions, statements, sentences, and utterances of sentences. Each has or has had its proponents, and the arguments pro and con are too subtle to be explored here. Two things should, however, be noted in this connection: first, that the issue is closely related to the problem of universals (i.e., whether what is known to be true is an abstract entity, such as a proposition, or whether it is a linguistic expression, such as a sentence or a sentence-token) and, second, that it is agreed by all sides that one cannot have knowledge, in this sense of “knowledge,” of that which is not true. One of the necessary conditions for saying that A knows that p is that p must be true, and this condition can therefore be regarded as one of the main elements in any accurate characterization of knowledge.
Index
Mental versus nonmental conceptions of knowledge. Philosophers have asked whether knowledge is a state of mind, i.e., a special kind of awareness of things. That it is has been argued by philosophers since at least the 5th century BC. In The Republic Plato provided the first extensive account of such a view. He regarded knowing as a mental faculty, akin to but different from believing or opining. Contemporary versions of this sort of theory regard knowing as one member of a sequence of mental states that involve increasing certitude. This spectrum would begin with guessing or conjecturing at the lowest end of certitude, would include thinking, believing, and feeling sure as expressing stronger attitudes of conviction, and would end with knowledge as the highest of all these states of mind. Knowledge, in all views of this type, is a form of consciousness, the strongest degree of awareness humans possess, and accordingly it is common for proponents of such views to hold that, if A knows that p, A must be conscious of what he knows. This view is normally expressed by saying that, if A knows that p, A knows that he knows that p.
Many 20th-century philosophers have rejected the notion that knowledge is a mental state. In On Certainty (1969) Ludwig Wittgenstein says: “‘Knowledge’ and certainty belong to different categories. They are not two mental states like, say surmising and being sure.” But, if knowing is not a mental state, then what is it? These philosophers have accepted the challenge of trying to give a different characterization of what it means to say that a person knows something. They typically begin by pointing out that a person can know that p without knowing that he knows it (a good example is in fact to be found in Plato’s Meno, where Socrates gradually elicits from a slave boy geometrical knowledge that the boy was not aware he had). They then proceed to argue that it is a mistake to assimilate cases of knowing to cases of doubting, feeling a pain, or having a certain opinion about something. All of these latter are mental states, and they are such that a person who has such a state is aware that he does.
These philosophers, moreover, typically deny that knowing can be described as being a single thing, such as a state of consciousness. Instead, they claim that one can ascribe knowledge to someone, or to oneself, when certain complex conditions are satisfied, among them certain behavioral conditions. For example, if a person can always give the right answers to questions under test conditions, one would be entitled to say that the person has knowledge of the issues under consideration. Knowing on this account seems tied to the capacity to perform in certain ways under certain standard conditions. Accordingly, though such performances may involve the exercise of intelligence or other mental factors, the attribution of knowledge to someone is not merely the attribution of a certain mental state or state of awareness to that person (as seen in the case of the slave boy in the Meno).
A well-known variant of such a view was advanced by J.L. Austin in his
1946 paper “Other Minds.”
Index
Occurrent versus dispositional
conceptions of knowledge
A distinction closely related to the previous one is that between occurrent and dispositional conceptions of knowledge. The difference between occurrences and dispositions can be illustrated with respect to sugar. A sugar cube will dissolve if put into water. One can thus say that, even if the cube is not now dissolving as it sits on the table, it will do so under certain conditions. This propensity to dissolve is what is meant by a disposition, and it is a feature sugar has at all times and in all conditions. It can be contrasted with sugar’s actually dissolving when immersed in liquid, which is an occurrence, that is, an event happening at a specific place and at a specific time.
These terms also apply to mental events. One can say of Smith, who is working on a problem, that he has just seen the solution. According to this way of speaking, there is a certain answer that Smith is presently aware of and to which he is attending. In such a case Smith’s knowledge is occurrent. But one can also ascribe a different sort of knowledge to Smith. Though Smith is perhaps not now thinking of his home address, he certainly knows it in the sense that, if he were asked, he could produce the correct answer. One can thus have knowledge that one is not aware of at a given moment. One can thus say, as with sugar, that knowledge may be either occurrent or dispositional in character, i.e., that one may or may not be in an immediate state of self-awareness with respect to p, but that in either case it can be said that the person knows that p.
It should be noted that the distinction between dispositional and occurrent knowledge thus applies to cases of “knowing that” as well as to cases of “knowing how” and thus is a powerful conceptual tool for analyzing different sorts of epistemic notions. The concept of a disposition has itself been further analyzed, for example by Roderick M. Chisholm (b. 1916), in counterfactual terms, and it has been proposed by many philosophers that the knowledge expressed by causal laws (laws of nature) is counterfactual and thus dispositional in character.
A priori versus a posteriori
knowledge
A sharp distinction has been drawn since at least the 17th century between two types of knowledge: a priori knowledge and a posteriori knowledge. The distinction plays an especially important role in the philosophies of David Hume (1711-76) and Immanuel Kant (1724-1804). It is also found in many contemporary, empirically oriented theories of knowledge, which typically hold that all knowledge about matters of fact derives from experience and is therefore a posteriori and that in consequence such knowledge is never certain but at most only probable.
The difference between these types of knowledge is easy to illustrate by means of examples. Consider the sentences “All husbands are married” and “All Model-T Fords are black” and assume that both statements are true. But how does one come to know that they are true? In the case of the first, the answer is that, if one thinks about the meaning of the various words in the sentence, one can see that the sentence is true. One can see that this is so because what is meant by “husband” is the same as what is meant by “married male.” Thus, by definition, every husband is a married male, and, accordingly, every husband is married. In calling such knowledge a priori, philosophers are pointing out that one does not have to engage in a factual or empirical inquiry in order to determine whether the sentence is true or not. One can know this merely on the basis of reflection and thus prior to or before any investigation of the facts.
In contrast, the second statement can be determined to be true only after such an investigation. One may well know that the Model-T Ford was an automobile built prior to World War II and accordingly would understand what all the words in the sentence mean. Nonetheless, understanding alone would not be sufficient to allow one to determine whether the sentence is true or not. Instead, some kind of empirical investigation is required in order to arrive at such a judgment; the knowledge thus acquired is a posteriori, or knowledge after the fact.
There are sets of distinctions related to the one just developed and in terms of which the two propositions can also be differentiated. They are necessary versus contingent, analytic versus synthetic, tautological versus significant, and logical versus factual.
Index
Necessary versus contingent
propositions
A proposition is said to be necessary if it holds (is true) under all possible circumstances or conditions. “All husbands are married” is such a proposition. There are no possible or conceivable conditions under which this statement would not be true (on the assumption, of course, that the words “husband” and “married” are taken to mean what they ordinarily mean). In contrast, “All Model-T Fords are black” holds in some circumstances (those actually obtaining, and that is why the proposition is true), but it is easy to imagine circumstances in which it would not be true - for instance, if somebody painted one of those cars a different colour. To say, therefore, that a proposition is contingent is to say that it holds in some but not in all possible circumstances. Some necessary propositions, such as “All husbands are married” are a priori (though not all are) and most contingent propositions are a posteriori.
Analytic versus synthetic
propositions
A proposition is often said to be analytic if the meaning of the predicate term is contained in the meaning of the subject term. Thus, “All husbands are married” is analytic because the term “husband” includes as part of its meaning “being married.” A term is said to be synthetic if this is not so. Therefore, “All Model-T Fords are black” is synthetic since the term “black” is not included in the meaning of “Model-T Ford.” Some analytic propositions are a priori, and most synthetic propositions are a posteriori. These distinctions were used by Kant to ask one of the most important questions in the history of epistemology, namely, whether a priori synthetic judgments are possible (see below for a discussion of this question).
Tautological versus significant
propositions
A proposition is said to be tautological if its constituent terms repeat themselves or if they can be reduced to terms that do, so that the proposition is of the form “a = a.” In such a case the proposition is said to be trivial and empty of cognitive import. A proposition is said to be significant if its constituent terms are such that the proposition does provide new information about the world. It is generally agreed that no significant propositions can be derived from tautologies. One of the objections to the ontological argument is that no existential (significant) proposition can be derived from the tautological definition of “God” with which the argument begins. Tautologies are generally known to be true a priori, are necessary, and are analytic; and significant statements are generally a posteriori, contingent, and synthetic.
In the ontological argument, for example, God is defined (roughly speaking) as the only perfect being. It is then argued that no being can be perfect unless it exists; therefore, God exists. But, as Hume and Kant pointed out, it is fallacious to derive a factual statement about the existence of God from the definition of God as a perfect being (see the discussion of St. Anselm below).
Index
Logical versus factual
propositions
The term “logical” in this connection is used in a wide sense to include a proposition such as “All husbands are married.” By analyzing the meaning of its constituent terms one can reduce the proposition to a logical truth, e.g., to “A and B implies A.” In contrast, factual propositions, such as “All Model-T Fords are black,” have syntactical and semantic structures that differentiate them from any propositions belonging to logic, even in the broad sense mentioned above. The theorems of logic are often a priori (though not always), are always necessary, and are typically analytic. Factual propositions are generally a posteriori, contingent, and synthetic.
These various distinctions are widely appealed to in present-day
philosophy. For instance, Saul
Kripke (b. 1941) in “Naming and Necessity” (1972) has used these notions in an
effort to solve a long-standing problem, namely, how true identity statements
can be nontrivial. The problem,
first articulated by Gottlob Frege in “On Sense and Reference” (1893) and later
independently addressed by Russell, begins with the assumption that the
sentences “Scott is Scott” and “Scott is the author of Waverley” are both
identity sentences and are true and that the former is trivial while the latter
is not. The puzzle arises from the
further assumption that any true identity sentence simply says of some object
that it is identical with itself. Hence, all such sentences should be
trivial. Clearly, however, “Scott
is the author of
Kripke argues that all true identity sentences are necessary (i.e., that they hold in all possible worlds) and that some of these, such as “Scott is Scott,” are known a priori and accordingly are trivial; but, he argues, some true identity sentences are not known a priori but only a posteriori and are not trivial. In cases of the latter sort, their nontriviality is a function of their being known to be true only after some sort of inquiry or investigation. It is the investigation that provides new information.
A good example would be the following. At one time in human history, ancient
peoples did not know that what they called “the evening star” was the same
planet called “the morning star.” But eventually the Babylonians discovered
through astronomical observation that the morning star is the planet Venus as it
appears in the morning sky and that the evening star is the planet Venus as it
appears in the evening sky. The
discovery that these two appearances are appearances of the same object amounted
to discovering more than that Venus is Venus. It provided new information, and that is
why “the morning star is identical with the evening star” is significant in a
way in which “Venus is Venus” is not, even though all of the descriptive terms
in both sentences refer to exactly the same object. In similar fashion, the a posteriori
finding that it was Scott who wrote
Knowledge by acquaintance and
knowledge by description
The distinction between knowledge by acquaintance and knowledge by description was introduced by Bertrand Russell in connection with his celebrated theory of descriptions. Here only the epistemological (as distinct from the logical) version of his theory will be considered. It was invented by Russell to lend support to the basic thesis of empiricism that all knowledge of matters of fact (i.e., all a posteriori knowledge) derives from experience. Russell’s program is both reductive and foundationalist. It tries to show that man’s system of knowledge is stratified: that some types of knowledge depend on others but that some do not and that the latter form the foundational units which give support to the whole epistemic system. He argued that, because these basic units rest upon direct experience, ultimately all factual knowledge is derivable from experience.
Russell’s argument begins with a distinction between two different types of knowledge, that which is and that which is not based on direct experience. Nearly all of man’s knowledge is of the latter type. For example, it is known that some 2,000 years ago there lived a Roman statesman named Augustus, that he was the successor to Julius Caesar, who had been assassinated, and that he was a friend of the historian Livy. But, since none of these pieces of information is presently known on the basis of personal experience, what justification is there for calling them instances of knowledge?
Russell argued that information based on direct experience is basic and needs no justification; he called it “knowledge by acquaintance.” Information not based on direct experience he called “knowledge by description.” One is justified in calling such information knowledge, if one can show that it can be traced back to and thus ultimately rests upon knowledge by acquaintance. To show how this is so in a particular case is to legitimate that particular piece of information as a specimen of knowing. Here is how this reductive process would work in the case of what is known about Augustus.
Whatever information people in the 20th century have about Augustus
probably comes to them from literary works, such as Livy’s history of
Russell’s reductive thesis then was that all legitimate specimens of knowledge are either based upon direct experience or can be shown to be dependent upon such direct experience via a chain of tight historical or causal links. His theory was therefore a form of empiricism, because it tried to show how all knowledge of matters of fact could be derived from experience.
But there is a further feature of the theory, stemming from the empirical tradition of John Locke (1632-1704) and David Hume, that gives a special twist to the notion of “knowledge by acquaintance.” According to this tradition, knowledge by acquaintance is always knowledge based upon what Hume called “impressions,” or upon what Russell called “sense-data.” These for Russell were mental entities that generally, but not always, reflected the characteristics actually possessed by physical objects. But, unlike physical objects, sense-data were the objects directly apprehended in an act of perception. What Russell meant by “direct apprehension” or “direct perception” was itself explicated in terms of the concepts of inference and non-inference. He held that direct perception, i.e., the perceptual awareness of a sense-datum, involves no inference and, accordingly, that knowledge by acquaintance is identical with the perception of sense-data.
The difference between inferential and noninferential perception can be illustrated by an example. Suppose one is working in a room and hears a sound that emanates from an outside source. (Russell considered hearing to be a form of perception.) In such a case the sound is a sense-datum. One need not infer that one is hearing a sound; there is a direct awareness of it. This would be a case of knowledge by acquaintance. On the basis of what one hears in this direct fashion, one might then infer (guess, conjecture, hypothesize) that what is causing the sound is a motorcycle located outside of the room, something that one who is in the room cannot see directly. If one is correct in this supposition, the information obtained in this way would be a case of indirect knowledge. In such a case, one’s knowledge that there is a motorcycle in the street is dependent on (and in Russell’s sense, reducible to) one’s direct awareness of a sound. The example illustrates how indirect knowledge, such as knowledge by description, is derived from direct knowledge, such as knowledge by acquaintance, and in turn how this latter depends upon the direct awareness of sense-data.
It should be mentioned that the distinction between knowledge by acquaintance and knowledge by description can be defended as legitimate and useful independently of a commitment to sense-data theory. In Russell’s work the objects of direct awareness are sense-data, but sense-data theory today has few proponents. A philosopher thus might hold that one at least sometimes directly perceives physical objects (which are not sense-data) while accepting that one’s knowledge of past events and persons is indirect and is thus knowledge by description.
Description versus
justification
Epistemology during its long history has engaged in two different sorts of tasks. One of these is descriptive in character. It aims to depict accurately certain features of the world, including the contents of the human mind, and to determine whether these should count as specimens of knowledge. A philosophical system with this orientation is, for example, the phenomenology of Edmund Husserl (1859-1938). Husserl’s aim was to give an exact description of the notion of intentionality, which he characterized as consisting of a certain kind of “directedness” toward an object. Suppose the object is an ambiguous drawing, such as the duck/rabbit sketch found in the Philosophical Investigations of Ludwig Wittgenstein. A person looking at the sketch is not sure whether it is a drawing of a duck or of a rabbit. Husserl claimed that the light rays reaching the eye from such an ambiguous drawing are identical whether one sees the image of a duck or of a rabbit and that the difference in perception is due to the viewer’s structuring of what he sees in the two cases. The theory tries to describe how such structuring takes place, and it ultimately becomes very complex in the account it gives.
In a famous passage in Philosophical Investigations (1953), Wittgenstein states that “explanation must be replaced by description,” and much of his work was devoted to carrying out that task, as, for example, in his account of what it is to follow a rule. Another example of descriptive epistemology is found in the writings of such sense-data theorists as Moore, Price, and Russell. They begin with the question of whether there are basic apprehensions of the world, free from any form of inference, and in those cases where they have argued that the answer is yes, they have tried to describe what these are and why they should count as instances of knowledge. Russell’s thesis that the whole edifice of knowledge is built up from a foundation composed of ingredients with which human beings are directly acquainted illustrates the close connection between the attempt to characterize various types of knowledge and this descriptive endeavour. The search by some logical positivists, such as Moritz Schlick (1882-1936), Otto Neurath (1882-1945), and A.J. Ayer (b. 1910) for protocol sentences, sentences that describe what is given in experience without inference, is a closely related example of this kind of descriptive practice.
Epistemology has a second function, which, in contrast to the descriptive one, is justificatory or normative. Philosophers concerned with this function start from the fact that all human beings have beliefs about the world, some of which are erroneous and some of which are not. The question to them is how one can justify (defend, support, or provide evidence for) certain sets of beliefs. The question has a normative import since it asks, in effect, what one ideally ought to believe. (In this respect epistemology has close parallels to ethics, where normative questions about how one ought ideally to act are asked.) This approach quickly takes one into the central domains of epistemology. It raises such questions as: Is knowledge identical with justified true belief? Is the relationship between evidence for a belief and the belief itself a probability function? If not, what is it? What indeed is meant by “justification” and what sorts of conditions have to be satisfied before one is entitled to say that a belief or set of beliefs is justified? These two differing aspects of epistemology are not inconsistent and indeed are often found intertwined in the writings of contemporary philosophers.
The relationship between knowledge and certainty is complex, and there is considerable disagreement about the matter. Are these concepts the same? If not, how do they differ? Is it possible for someone to know that p without being certain that p? Is it possible for someone to be certain that p without knowing that p? These are the central issues around which the debate revolves. The various answers that have been proffered depend on how the concepts of knowledge and certainty are analyzed. If one holds, for instance, that knowing is not a psychological state but that certainty is, then one would deny that the concepts are identical. But if one holds that knowing represents the highest degree of assurance which humans can obtain with respect to the truth of p, and that such a maximal degree of assurance is a psychological state, one will interpret the concepts to be equivalent. There have been proponents on both sides of this issue.
Further complicating the discussion are subtle distinctions drawn by
20th-century philosophers. For
instance, in “Certainty” (1941) G.E. Moore claimed that there are four main
types of idioms in which the word “certain” is commonly used: “I feel certain
that,” “I am certain that,” “I know for certain that,” and finally “It is
certain that.” He points out that
“I feel certain that p” may be true when p is not true but that there is at
least one use of “I know for certain that p” and “It is certain that p” which is
such that neither of these sentences can be true unless p is true.
The most radical position on these matters is to be found in
Wittgenstein’s On Certainty,
published posthumously in 1969. Wittgenstein holds that knowledge is
radically different from certitude and that neither concept entails the other.
It is thus possible to be in a
state of knowledge without being certain and to be certain without having
knowledge. As he writes: “Instead
of ‘I know”.... couldn’t
Index
Philosophers not only wish to know what knowledge is but also how it originates. This motivation is based, at least in part, on the supposition that an investigation into the provenance of knowledge can help cast light on its nature. From the time of the Greeks to the present, therefore, one of the major themes of epistemology has been a quest into the sources of knowledge.
Plato’s The Republic contains one of the earliest systematic arguments to the effect that sense experience cannot be a source of knowledge. The argument begins with the assertion that ordinary persons have a clear grasp of certain concepts, that of equality, for instance. In other words, people know what it means to say that A and B are equal, no matter what A and B are. But where does such knowledge come from? One may wonder, for instance, whether it is provided by vision and consider the claim that two pieces of wood are of equal length. A close inspection of these pieces of wood, however, shows them to differ slightly, and the more detailed the inspection, via various degrees of magnification, the more disparity one notices. It follows that visual experience cannot be the fount of the concept of equality. Plato applies this result to the operations of all the five senses and concludes that sense experience in general cannot be the origin of such knowledge. It must therefore have another source, which he regards as prenatal (one such account is found in the myth of Er in Book X).
The mathematical example Plato selects to illustrate that the origin of knowledge is not in sense experience is highly significant; indeed it is one of the signs of his perspicacity that he should pick such an example. For, as the subsequent history of philosophy reveals, the strongest case for the notion that at least some knowledge does not derive from sense experience lies in mathematics. Mathematical entities are abstractions - perfect triangles, disembodied surfaces and edges, lines without thickness, and extensionless points - and none of these exists in the physical world, i.e., the world apprehended by the senses. It might be thought that, had Plato selected a different example, say, the colour red, his argument would have been less convincing. But it is a further sign of his genius that he discusses colours as well as mathematical notions and provides good reasons for holding that seeing examples or specimens of red (or any other colour) is not equivalent to knowing what that colour is. Such knowledge must therefore have a different genesis than sense experience.
The puzzle about origins of knowledge has led historically to two different kinds of issues. One of these is the question of whether knowledge (or at least certain kinds of knowledge) is innate, meaning that it is not acquired or learned through experience but in some important sense is present in the human psyche at birth. The matter is still a live issue today, not only in philosophy but also in linguistics and psychology. The linguist Noam Chomsky (b. 1928), for example, has asserted that the “projection phenomenon” - the ability of children to construct sentences that they have never heard before and that are grammatical - is proof of inherent conceptual structures, whereas the experimental psychologist B.F. Skinner (b. 1904) has tried to show that all knowledge is the product of learning through environmental conditioning by means of the processes of reinforcement and reward.
In the extensive historical literature on this topic both the notion of “innateness” and that of “learning” have been given various interpretations. Sometimes, for instance, innateness carries only the sense of a disposition or propensity, but in stronger versions of the thesis, such as Plato’s, it is affirmed that humans possess actual pieces of prenatal knowledge. “Learning” also is given a variety of meanings, ranging from trial-and-error methods to inexplicit types of “absorption” of information. There are also a range of “compromise” theories. These typically claim that humans have some knowledge that is innate - the awareness of God, the principles of moral rightness and wrongness, and certain mathematical theorems being favoured examples - whereas other kinds of knowledge - such as knowledge by acquaintance - are gained through experience.
The second issue that emerges from considerations of the origins of knowledge focuses on the distinction between rationalism and empiricism. Though closely related to the issue of innateness versus learning, the question in this case concerns the nature of the source from which knowledge arises. The history of discussion of the issue indicates that two main sources have been identified and argued for: reason and experience.
Rationalism is the thesis that the ultimate source of knowledge is to be found in human reason. What reason is, in turn, is a difficult question. But, generally speaking, it is assumed that reason is a feature of the human mind that differs not just in degree but in kind from bodily sensations, feelings, and certain psychological attitudes, such as disgust or enthusiasm. For some writers, such as Plato, reason is a faculty, a special facility or structure of the mind. Many later philosophers reject any sort of faculty psychology, and some of them tend to interpret reason in dispositional or behavioral ways. But, whatever the interpretation, a rationalist must hold that reason has a special power for grasping reality. It is the exercise of reason that allows human beings to understand the world they live in. Such a thesis is double-sided: it holds, on the one hand, that reality is in principle knowable and, on the other hand, that there are human, distinctively mental, powers capable of apprehending it. One thus might define rationalism as the theory that there is an isomorphism (a mirroring relationship) between reason and reality which makes it possible for the former to apprehend the latter just as it is. Rationalists affirm that, if such a correspondence were lacking, the effort of human intelligence to understand the world would be impossible.
Empiricism is often defined as the doctrine that all knowledge comes from experience. Almost no philosopher, however, has ever literally held that all knowledge comes from experience. Locke, who is the empiricist par excellence, thought there is some knowledge human beings have - which he calls “trifling ideas” (or trivialities), such as a = a - that does not derive from experience; but he regarded such knowledge as empty of content. Hume held similar views.
Empiricism thus generally allows for a priori knowledge while denigrating its significance, and accordingly it is more accurate to define it as the theory that all knowledge about matters of fact derives from experience. When defined in this way empiricism does represent a significant contrast to rationalism. Rationalists hold that human beings have knowledge about matters of fact which is anterior to experience and yet which does tell them something significant about the world and its various features. Empiricists would deny that this is possible.
The meaning of the term experience is generally limited to the impressions and sensations received by the senses. Thus, knowledge is the information apprehended by the five sense modalities - hearing, seeing, touching, tasting, and smelling. Such knowledge is always about matters of fact, about what one can see, touch, hear, taste, or smell. For strict empiricists this definition has the implication that the human mind is passive - a tabula rasa, in Locke’s idiom; it is an organ that receives impressions and more or less records them as they are. This conception of the mind has seemed counterintuitive to many philosophers, especially those in the Kantian tradition. But it also poses serious challenges for empiricists. For example, it raises the question of how one can have knowledge of items, such as a dragon, that cannot be found in experience.
In response, the classical empiricists such as Locke and Hume have tried to show how the complex concept of a dragon can be reduced to simple concepts (such as wings, the body of a snake, the head of a horse), all of which derive from direct impressions of such items. On such a view the mind is still considered to be primarily passive, but it is conceded that it has some active functions, such as being able to combine simple impressions and ideas into complex ideas.
There are further difficulties: the empiricist must explain how abstract ideas, such as the concept of a perfect triangle, can be reduced to elements apprehended by the senses when no perfect triangles are actually found in nature, and he must also give an account of how general notions are possible. It is obvious that one does not experience “mankind,” but only particular individuals, through the senses; yet such general notions are meaningful, and propositions containing these concepts are known to be true. The same difficulty applies to colour concepts. Some empiricists have argued that one arrives at the concept of red, for example, by abstracting from individual items that are red. But the difficulty with this suggestion is that one would not know what to count as an instance of red unless one already had such a concept in mind; and, if that is so, it would seem that experience cannot be the source of the concept. It is generally felt that, despite ingenious attempts by empiricists to deal with such issues, their solutions have not been wholly successful. Indeed, the history of epistemology has to a large extent been a dialectic between rationalism and empiricism in an effort to meet skeptical challenges that are designed to undermine both positions.
Index
Many philosophers past and present and many nonphilosophers who are studying philosophy for the first time have been struck by the seemingly indecisive nature of philosophical argumentation. For every argument, there seems to be a counterargument; and for every position, a counterposition. To a considerable extent skepticism is born of such reflection. Some of the ancient skeptics contended, for example, that all arguments are equally bad and, accordingly, that nothing can be proved. The American philosopher Benson Mates claims to be a modern representative of this tradition, except that he believes all philosophical arguments to be equally good. But he insists that, because they are, they invariably issue in conceptual deadlocks and resolve nothing.
Ironically, skepticism is itself a type of philosophy, and the question has been raised whether it manages to escape its own demurrers. Does it offer arguments, and, if so, are they decisive? The answers to these questions depend on what is meant by skepticism. Historically, the term refers to a complex set of practices taking many different forms - from stating explicit theories to assuming negative attitudes without much propositional content. Thus, it is difficult to define. But, however it is understood, skepticism represents a set of challenges to the claim that human beings do possess or can acquire knowledge.
In giving even this minimal characterization, it is important to
emphasize that both dogmatists and skeptics accept a definition of knowledge
that implies two things: that, if a person, A, knows that p, then p is true and
that, if a person, A, knows that p, then A cannot be mistaken, meaning that it
is logically impossible that A could be wrong. If a person says that he knows Smith will
arrive at
It should also be stressed that, given this definition of knowledge, the skeptic does not have to show that A is actually mistaken in claiming to know that p. All he has to show is that it is possible that A might be mistaken. Hence arises the skeptic’s practice of searching for a possible counterexample to a claim. If A states that he has had a certain experience, for instance, that of having personally spoken with Smith, who assured him he would keep his appointment at 9:00 AM, then the skeptic can point out that, although one could have such an experience, it is still possible that Smith might not show up; and, if so, A’s claim to know is untenable. In effect, by emphasizing the notion of possibility, the skeptic is pointing out that there is a logical gap between the criteria that support the claim and the claim itself. The criteria might be satisfied, and yet the claim might be false; but, if such a possibility exists, the original assertion cannot be a specimen of knowing.
More generally, radical skepticism has tried to show that one might (i.e., could possibly) have all the experiences associated with normal perception or behaviour and yet be wholly mistaken in thinking that these experiences correlate with anything in the external world. For example, a brain in a vat might be programmed by scientists to have the sensation of seeing a tree, even though it is not in fact seeing a tree. Thus, there is a gap between the experience the brain is having and external reality; accordingly, its claim to know on the basis of such a visual experience is mistaken. The skeptic’s point is that the disparity between external reality and felt experience is always possible and, accordingly, that knowledge claims based upon such experience cannot be defended.
The ability to find counterexamples explains why skeptics do not challenge but indeed accept the dogmatist’s definition of knowledge. That they do so is important because it means that they are not arguing at cross-purposes with their opponents. What they challenge is not the meaning of knowledge but the contention that anybody actually has knowledge in that sense.
Nearly all of the major epistemological theories of philosophy have given rise to skeptical reactions. Many of the greatest thinkers in the Western tradition have assumed that by means of reason or sense experience one can come to have knowledge of reality. But skepticism has challenged the validity of both of these appeals. Skeptics have developed wholesale arguments to undermine the efforts to show that reason and sense experience, which seem to be the only possible candidates, are reliable sources of knowledge. Descartes, for example, considered the hypothesis that an evil genius may delude people into thinking that they are experiencing the real world when they are not. With regard to major epistemological problems, such as the “other-minds problem,” the problem of memory, the problem of induction, and the problem of self-knowledge, skeptical doubts have challenged the validity of reason and of sense experience and thus of claims to have knowledge of various aspects of reality. How some of these moves and countermoves actually take place are addressed below.
Avrum Stroll
Index
The central focus of ancient Greek philosophy was its attempt to solve the problem of motion. Many pre-Socratic philosophers thought that no logically coherent account of motion and change could be given. This problem was a concern of metaphysics, not epistemology, however, and in the present context it suffices merely to allude to the arguments of Parmenides and Zeno of Elea against the possibility that anything moves or changes. The consequence of this position for epistemology was that all major Greek philosophers held that knowledge must not itself change or be changeable in any respect. This requirement motivated Parmenides, for example, to hold that thinking is identical with being (what exists or is unchanging) and that it is impossible to think of “nonbeing” or “becoming” (what changes) in any way.
Plato (c. 427-347 BC) accepted the Parmenidean constraint on any theory of knowledge that both knowledge and its objects must be unchanging. One consequence of this, as Plato pointed out in Theaetetus, is that knowledge cannot have physical reality as its object. In particular, since sensation and perception have various kinds of motions as their objects, knowledge cannot be the same as sensation or perception. The negative thesis of Plato’s epistemology consists, then, in the denial that sense experience can be a source of knowledge on the ground that the objects apprehended through the senses are subject to change. To the extent that humans have knowledge, they attain it by transcending the information provided by the senses in order to discover unchanging objects. But this can be done only by the exercise of reason, and in particular by the application of the dialectical method of inquiry inherited from Socrates.
The Platonic theory of knowledge is thus divided into two parts: a quest first to discover whether there are any unchanging objects and to identify and describe them and second to illustrate how they could be known by the use of reason, that is, via the dialectical method. Plato used various literary devices for illustrating his theory; the most famous of these is the allegory of the cave in Book VII of The Republic. The allegory depicts ordinary people as living locked in a cave, which represents the world of sense-experience; in the cave people see only unreal objects, shadows, or images. But through a painful process, which involves the rejection and overcoming of the familiar sensible world, they begin an ascent out of the cave into reality; this process is the analogue of the application of the dialectical method, which allows one to apprehend unchanging objects and thus acquire knowledge. In the allegory, this upward process, which not everyone is competent to engage in, culminates in the direct vision of the sun, which represents the source of knowledge.
In searching for unchanging objects, Plato begins his quest by pointing out that every faculty in the human mind apprehends a set of unique objects: hearing apprehends sounds but not odours; the sense of smell apprehends odours but not visual images; and so forth. Knowing is also a mental faculty, and therefore there must be objects that it apprehends. These have to be unchanging, whatever they are. Plato’s discovery is that there are such entities. Roughly, they are the items denoted by predicate terms in language: such words as “good,” “white,” or “triangle.” To say “This is a triangle” is to attribute a certain property, that of being a triangle, to a certain spatiotemporal object, such as a particular figure drawn on a blackboard. Plato is here distinguishing between specific triangles that can be drawn, sketched, or painted and the common property they share, that of being triangular. Objects of the former kind he calls particulars. They are always located somewhere in the space-time order, that is, in the world of appearance. But such particular things are different from the common property they share. That is, if x is a triangle, and y is a triangle, and z is a triangle, x, y, and z are particulars that share a common property, triangularity. That common property is what Plato calls a “form” or “idea” (not using this latter term in any psychological sense). Unlike particulars, forms do not exist in the space-time order. Moreover, they do not change. They are thus the objects that one must apprehend in order to acquire knowledge.
Similar remarks apply, for example, to goodness, whiteness, or being to the right of. Particular things change; they come into and go out of existence. But whiteness never changes, and neither does triangularity; and, if they do not change, they are not subject to the ravages of time. In that sense, they are eternal.
The use of reason for discovering unchanging forms is exercised in the dialectical method. The method is one of question and answer, designed to elicit a real definition. By a “real definition” is meant a set of necessary and sufficient conditions that exactly delimit a concept. One may, for example, consider the concept of being the brother of Y. This can be explained in terms of the concepts of being male and of being a sibling of Y. These concepts together lay down necessary and sufficient conditions for anything’s being a brother. One who grasps these conditions understands precisely what it is to be a brother.
The Republic begins with the use of the dialectical method to discover what justice is. Cephalus proposes the thesis that “justice” means the same as “honesty in word and deed.” Socrates searches for and finds a counterexample to this proposal. It is just, he points out, under some conditions, not to tell the truth or to repay debts. If one had borrowed a weapon from an insane person, who then demanded it back in order to kill an innocent person, it would be just to lie to him, stating that one no longer had the weapon. Therefore, “justice” cannot mean the same as “honesty in word” (i.e., telling the truth). By this technique of proposing one definition after another and subjecting each to possible counterexamples, Socrates attempts to find a definition that would be immune to counterexamples. To find such a definition would be to define the concept of justice, and in this way to discover the true nature of justice. In such a case one would be apprehending a form, the common feature that all just things share.
Plato’s search for definitions and thereby the nature of forms is a
search for knowledge. But how
should knowledge in general be defined? In Theaetetus Plato argues that it involves
true belief. No one can know what
is false. A person may mistakenly
believe that he knows something, which is in fact false, but this is only
thinking that one knows, not knowing. Thus, a person may confidently assert, “I
know that
Although it is difficult to explain what justification is, most philosophers accepted the Platonic analysis of knowledge as fundamentally correct until 1963, when the American philosopher Edmund L. Gettier produced a counterexample that shook the foundations of epistemology: suppose that Kathy knows Oscar very well and that Oscar is behind her, out of sight, walking across the mall. Further, suppose that in front of her she sees walking toward her someone who looks exactly like Oscar; unbeknownst to her, it is Oscar’s twin brother. Kathy forms the belief that Oscar is walking across the mall. Her belief is true, because he is walking across the mall (though she does not see him doing it). And her true belief seems to be justified, because she formed it on the same basis she would have if she had actually seen Oscar walking across the mall. Nonetheless, Kathy does not know that Oscar is walking across the mall, because the justification for her true belief is not the right kind. What her true belief lacks is an appropriate causal connection to its object.
Index
In Posterior Analytics, Aristotle (384-22 BC) analyzes scientific knowledge in terms of necessary propositions that express causal relations. Such knowledge takes the form of categorical syllogisms, in which the middle term causally and necessarily connects the major and minor terms. For example, because all stars are distant and all distant objects twinkle, it follows that all stars twinkle. That is, the middle term, “distant objects,” connects the minor term, “stars,” to the major term, “twinkle,” in order to yield the conclusion that all stars twinkle. Aristotle, however, recognizes that not all knowledge is provable. Thus, the premises of the most basic syllogisms are known but not provable. In contrast with scientific knowledge, there is opinion, which is not provable and is about what happens to be true but need not be.
Since the knowledge formulated in syllogisms resides in the mind, which is part of or one faculty of the soul, much of what Aristotle says about knowledge is part of his doctrine about the nature of soul and, in particular, human soul. As he uses the term, every living thing, including plant life, has a soul (psyche), a soul being what makes a thing alive. Thus it is important not to equate soul with mind or intellect. The intellect (nous) might variously be described as a power, faculty, part, or aspect of the human soul. It should be stressed that for Aristotle the terms soul (psyche) and intellect (nous) and its constituents were understood to be scientific terms.
Knowledge is something that a person has. Thus it must be in him somewhere, and the location must be his mind or intellect. Yet there can be no knowledge if the knower and the thing known are wholly separate. What then is the relation between the knowledge in the person or his mind and the object of his knowledge? Aristotle’s answer is one of his most enigmatic claims. He says, “Actual knowledge is identical with its object.”
Here is one suggestion about what Aristotle means. When a person learns something, he acquires something. What he acquires must either be something different from the thing he knows or identical with it. If it is something different, then there is a discrepancy between what he has in mind and the intended object of his knowledge. But such a discrepancy seems to be incompatible with the existence of knowledge. For knowledge, which must be true and accurate, cannot deviate from its object in any way. One cannot know that blue is a colour if the object of that knowledge is something other than that blue is a colour. This idea that knowledge is identical with its object is dimly reflected in the repetition of the variable p in the standard formula about knowledge: S knows that p just in case it is true that p. Although the line of thinking being attributed to Aristotle is defective in several ways, something like it seems to have motivated Aristotle and many other thinkers over the centuries.
To assert that knowledge and its object must be identical raises a question: In what way is knowledge in a person? Suppose that Smith knows Fido. Then Fido is in Smith. Obviously, Fido is not there as he exists in the nonmental world of space and time. In what sense can it be true that a person who knows what a dog is has that object in his mind? Aristotle derives his answer from his general theory of reality. According to him, all (terrestrial) substances are composed of two principles: matter and form. If there are four dogs - Bowser, Fido, Spot, and Spuds - they are the same in some respect and different in some respect. They are the same in that each belongs to the same kind and each functions similarly. Thus, Aristotle reasons, just as Plato had, that there must be something in virtue of which they are the same, and this he calls “form.” That is, Bowser, Fido, Spot, and Spuds each have the very same form of being a dog. They are different in that they are made out of different matter, different parcels of stuff. The form that a thing has is more important than its matter because it is the form that makes the thing what it is. If Fido were to lose the form of being a dog and acquire another, he would no longer be the same thing. The stuff out of which Fido is made is not similarly important, and in fact that stuff changes periodically, as body cells change through metabolic processes, without Fido ceasing to be Fido.
To return to the explanation of knowledge, what is in the knower when he knows what dogs are is the form of being a dog minus the matter. According to Aristotle, matter is literally unintelligible and not essential to what Fido or any other dog is; thus its absence is inconsequential for knowledge, though not for Fido.
In his sketchy account of the process of thinking in De anima (On the Soul), Aristotle says that the intellect, like everything else, must have two parts: something analogous to matter and something analogous to form. The first of these is the passive intellect; the second is active intellect, of which Aristotle speaks tersely. “Intellect in this sense is separable, impassible, unmixed, since it is in its essential nature activity… When intellect is set free from its present conditions it appears as just what it is and nothing more: it alone is immortal and eternal… and without it nothing thinks.”
This part of Aristotle’s views about knowledge is an extension of what he says about sensation. According to Aristotle, sensation occurs when the sense organ is stimulated by the sense object, typically through some medium, such as light for vision and air for hearing. This stimulation causes a “sensible species” to be generated in the sense organ itself. This “species” is some sort of representation of the object sensed. As Aristotle describes the process, the sense receives “the form of sensible objects without the matter, just as the wax receives the impression of the signet-ring without the iron or the gold.” But, since there are different species for each of the five external senses that Aristotle recognized - sight, hearing, touch, taste, and smell - “species” does not mean “image.”
After the development of Aristotle’s psychology the next significant event for the theory of knowledge was the rise of Skepticism, of which there were at least two kinds. The first, Academic Skepticism, arose in the Academy after Plato’s death and was propounded by the Greek philosopher Arcesilaus (c. 315 - c. 240 BC), about whom the philosophers Cicero, Sextus Empiricus, and Diogenes Laërtius provide information. Academic Skepticism is also called “dogmatic Skepticism” when it is interpreted as arguing for the thesis that nothing is known. The thesis was inspired by Socrates’ avowal that the only thing he knew was that he knew nothing. Thus, it asserts that knowledge is impossible. This form of Skepticism seems to be susceptible to an objection raised by the Stoic Antipater (fl. c. 135 BC) and others that the view is self-contradictory. To know that knowledge is impossible is to know something; hence, dogmatic Skepticism is false.
Carneades (c. 213-129 BC), a member of the Academy, gave a subtle reply. Academic Skepticism, he claimed, should not be interpreted as a claim about how the world is in itself or about a correspondence between thought (or language) and the world, but as a judicial decision. Just as a defendant in a trial does not prove his innocence but relies upon its presumption and defends it against attack, so the Skeptic does not try to prove that he knows nothing but presumes it and defends this presumption against attacks.
Carneades’ construal of Academic Skepticism brings it close to the other
kind, Pyrrhonism, named after Pyrrho of Elis (c. 365-275 BC). None of his works survive, and scholars
rely principally on the early 3rd-century-AD writings of Sextus Empiricus to
understand Pyrrhonism. Pyrrhonists
assert or deny nothing but lead people to give up making any claims to
knowledge. The Pyrrhonist’s
strategy is to show that, for each proposition with some evidence for it, an
opposed proposition has equally good evidence supporting it. These arguments for refuting each side of
an issue are called “tropes.” For
example, the judgment that a tower is round when seen at a distance is
contradicted by the judgment that the tower is square when seen up close. The judgment that
Pyrrhonists diagnose dogmatism as the unjustifiable preference for one mode of existence over another. Dogmatists prefer wakefulness and sanity over sleep and insanity. But why should sleep and insanity not be the norm? If the dogmatist answers that it is because sleep and insanity involve some deficiency or abnormal physical states, the Skeptic replies, “By what nonquestion-begging criterion are these things said to be deficient or abnormal? Why should insanity not be taken as the primary notion and sanity be defined as the lack of insanity? If it were, then it would not be difficult to see sanity as a deficiency or abnormality, just as insanity currently is. Or why should wakefulness not be seen as the deficient condition in which people do not dream?” The Skeptic does not advocate insanity or sleep but merely argues that a preference for them is no less justified than a preference for sanity and wakefulness.
What is at stake in the preceding Skeptical arguments is “the problem of the criterion,” that is, the problem of deciding how one can determine a justifiable standard against which to measure judgments. Truth seems to need a criterion. But every criterion is either groundless or inconclusive. Suppose that something is proffered as a criterion. The Skeptic will ask what proof there is for it. If no proof is offered, the criterion is groundless. If, on the other hand, a proof is produced, a vicious circle begins to close around the dogmatist: What judgment justifies belief in the proof? If there is no judgment, the proof is unsupported; and if there is a judgment, it requires a criterion, which is just what the dogmatist was supposed to have provided in the first place.
If the Skeptic needed to make judgments in order to survive, he would be in trouble. In fact there is another method of survival that bypasses judgment. The Skeptic can live quite nicely, according to Sextus, by following custom and the way things appear to him. In doing this, the Skeptic does not judge the correctness of anything but merely accepts appearances for what they are.
Ancient Pyrrhonism is not strictly an epistemology since it has no theory of knowledge and is content to undermine the dogmatic epistemologies of others, especially of the Stoics and Epicureans. Pyrrho himself was said to have had moral and ethical motives for attacking dogmatists. Being reconciled to not knowing anything, Pyrrho thought, induced serenity (ataraxia).
St. Augustine of Hippo (354-430) claimed that human knowledge would be impossible if God did not illumine the human mind and thereby allow it to see, grasp, or understand ideas. There are two components to his theory: ideas and illumination. Ideas as Augustine construed them are the same as Plato’s; they are timeless, immutable, and accessible only to the mind, not to the senses. They are indeed in some mysterious way part of God and seen in God. Illumination, the other element of the theory, was for Augustine and his many followers, at least through the 14th century, a technical term, built upon a metaphor. Since the mind is immaterial, it cannot be literally lighted. Yet the entire theory of illumination rested upon the extended visual metaphor, inherited from Plotinus (205-270) and other Neoplatonic sources, of the human mind as an eye that can see when and only when God, the source of light, illumines it. Still, it is a powerful metaphor relied upon even in the 17th century by René Descartes (Discourse on Method; 1637). Varying his metaphor, Augustine sometimes says that the human mind participates in God and even, as in On the Teacher, that Christ illumines the mind by dwelling in it. It is important to emphasize that Augustine’s theory of illumination concerns all knowledge, and not specifically mystical or spiritual knowledge. In addition to its historical significance, his theory is interesting for showing how diverse epistemological theories have been.
Before he articulated this theory in his mature years and soon after his conversion to Christianity, Augustine was concerned to refute the Skepticism of the Academy. In Against the Academicians Augustine claims that, if nothing else, humans know such disjunctive tautologies as that either there is one world or there is not one world and that either the world is finite or it is infinite. Humans also know many propositions that begin with the phrase “It appears to me that,” such as “It appears to me that what I perceive is made up of earth and sky, or what appears to be earth and sky.” And they know logical (or what he calls “dialectical”) propositions, for example, “If there are four elements in the world, there are not five; if there is one sun, there are not two; one and the same soul cannot die and still be immortal; and man cannot at the same time be happy and unhappy.”
Many other refutations of Skepticism occur in later works, notably, in On the Free Choice of the Will, On the Trinity, and The City of God. In the latter work Augustine proposes other examples of things about which people are absolutely certain. Again in explicit refutation of the Skeptics of the Academy, Augustine argues that if a person is deceived, then it is certain that he exists. Like Descartes, Augustine puts the point in the first person, “If I am deceived, then I exist” (Si fallor, sum). A variation on this line of reasoning occurs in On the Trinity, when he says that if he is deceived, he is at least certain that he is alive.
Augustine also points out that, since he knows, he knows that he knows; and he notes that this can be reiterated an infinite number of times: If I know that I know that I am alive, then I know that I know that I know that I am alive. This point was codified in 20th-century epistemic logic as the axiom “If X knows that p, then X knows that X knows that p.” In The City of God Augustine claims that he knows that he loves: “For neither am I deceived in this, that I love, since in those things which I love I am not deceived.” With Skepticism thus refuted, Augustine simply denies that he has ever been able to doubt what he had learned through his sensations or even the testimony of most people.
Skepticism did not recover from Augustine’s criticisms for a thousand years; but then it arose again like the phoenix in Egyptian mythology. Augustine’s Platonic epistemology dominated the Middle Ages until the mid-13th century, when St. Albertus Magnus (1200-80) and then his student St. Thomas Aquinas developed an alternative to Augustinian illuminationism.
Index
The Competitiveness of Nations
in a Global Knowledge-Based Economy
January 2003