People use the word “know” all the time, but what does it mean? Most of us feel that we have an intuitive grasp of the concept, but providing a more rigorous analysis of it is difficult.
Philosophers typically divide knowledge into three types: personal knowledge, procedural knowledge, and propositional knowledge. The primary concern of epistemology is propositional knowledge, but contrasting this with other types of knowledge can help in clarifying precisely what it is that epistemologists are discussing.
The most popular account of knowledge is the tripartite theory. This theory, which analyses knowledge as justified true belief, is widely used as a working model, even though most philosophers recognise that it has serious difficulties.
The closest thing to a rival to the tripartite theory is infallibilism, which suggests that knowledge requires absolute certainty, as opposed to belief or opinion about which there is more doubt.
What is Knowledge?
– Types of Knowledge
– Theories of Knowledge
Theory of Knowledge
http://www.theoryofknowledge.info/what-is-knowledge/
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Theory of Knowledge
http://www.theoryofknowledge.info/
Epistemology, the study of the theory of knowledge, is among the most important areas of philosophy. The questions that it addresses include the following:
What is knowledge?
The first problem encountered in epistemology is that of defining knowledge. Much of the time, philosophers use the tripartite theory of knowledge, which analyses knowledge as justified true belief, as a working model. The tripartite theory has, however, been refuted: Gettier cases show that some justified true beliefs do not constitute knowledge. Rival analyses of knowledge have been proposed, but there is as yet no consensus on what knowledge is. This fundamental question of epistemology remains unsolved.
Though philosophers are unable to provide a generally accepted analysis of knowledge, we all understand roughly what we are talking about when we use words such as “knowledge”. Thankfully, this means that it is possible to get on with epistemology, leaving unsolved the fundamental question as to what knowledge is.
From where do we get our knowledge?
A second important issue in epistemology concerns the ultimate source of our knowledge. There are two traditions: empiricism, which holds that our knowledge is primarily based in experience, and rationalism, which holds that our knowledge is primarily based in reason. Although the modern scientific worldview borrows heavily from empiricism, there are reasons for thinking that a synthesis of the two traditions is more plausible than either of them individually.
How are our beliefs justified?
There are better and worse ways to form beliefs. In general terms, it is important to consider evidence when deciding what to believe, because by doing so we are more likely to form beliefs that are true. Precisely how this should work, when we are justified in believing something and when we are not, is another topic in the theory of knowledge. The three most prominent theories of epistemic justification are foundationalism, coherentism, and reliabilism.
How do we perceive the world around us?
Much of our knowledge, it seems, does come to us through our senses, through perception. Perception, though, is a complex process. The way that we experience the world may be determined in part by the world, but it is also determined in part by us. We do not passively receive information through our senses; arguably, we contribute just as much to our experiences as do the objects that they are experiences of. How we are to understand the process of perception, and how this should effect our understanding of the world that we inhabit, is therefore vital for epistemology.
Do we know anything at all?
The area of epistemology that has captured most imaginations is philosophical scepticism. Alongside the questions of what knowledge is and how we come to acquire it is the question whether we do in fact know anything at all. There is a long philosophical tradition that says that we do not, and the arguments in support of this position, though resisted by most, are remarkably difficult to refute. The most persistent problem in the theory of knowledge is not what knowledge is or what it comes from, but whether there is any such thing at all.
Types of Knowledge
http://www.theoryofknowledge.info/what-is-knowledge/types-of-knowledge/
Philosophers typically divide knowledge into three categories: personal, procedural, and propositional. It is the last of these, propositional knowledge, that primarily concerns philosophers. However, understanding the connections between the three types of knowledge can be helpful in clearly understanding what is and what is not being analysed by the various theories of knowledge.
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Personal Knowledge
http://www.theoryofknowledge.info/what-is-knowledge/types-of-knowledge/personal-knowledge/
The first type of knowledge is personal knowledge, or knowledge by acquaintance.
Knowledge in this sense is to do with being familiar with something: in order to know Amy, one must have met her; in order to know fear, one must have experienced it. In each of these cases, the word “know” is being use to refer to knowledge by acquaintance.
Personal knowledge does, arguably, involve possessing at least some propositional knowledge. If I have met Amy, but can’t remember a single thing about her, then I probably wouldn’t claim to know her. In fact, knowing a person (in the sense required for knowledge by acquaintance) does seem to involve knowing a significant number of propositions about them.
What is important is that personal knowledge involves more than knowledge of propositions. No matter how much you tell me about Amy, no matter how many facts about her I learn, if I haven’t met her then I can’t be said to know her in the sense required for personal knowledge.
Personal knowledge thus seems to involve coming to know a certain number of propositions in a particular way.
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Procedural Knowledge
http://www.theoryofknowledge.info/what-is-knowledge/types-of-knowledge/procedural-knowledge/
The second kind of knowledge is procedural knowledge, or knowledge how to do something. The claims to know how to juggle and how to drive are claims to have procedural knowledge.
Procedural knowledge clearly differs from propositional knowledge. It is possible to know all of the theory behind driving a car (i.e. to have all of the relevant propositional knowledge) without actually knowing how to drive a car (i.e. without having the procedural knowledge).
You may know which pedal is the accelerator and which is the brake. You may know where the handbrake is and what it does. You may know where your blind spots are are when you need to check them. But until you get behind the wheel and learn how to apply all this theory, you do not know how to drive.
Knowing how to drive involves possessing a skill, being able to do something, which is very different to merely knowing a collection of facts.
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Propositional Knowledge
http://www.theoryofknowledge.info/what-is-knowledge/types-of-knowledge/propositional-knowledge/
Although there are several different types of knowledge, the primary concern of epistemology is propositional knowledge. This is knowledge of facts, knowledge that such and such is the case.
The difference between the three types of knowledge is not as sharp as it might at first appear.
Personal knowledge does seem to involve knowledge of at least some propositions. Simply having met someone is not enough to know them (in the personal knowledge sense); you also have to know a few things about them (in the propositional knowledge sense).
Procedural knowledge also seems to involve some propositional knowledge. If you know how to drive a car (in the procedural knowledge sense) then you presumably know certain facts about driving (e.g. which way the car will go if you turn the steering wheel to the left).
What is important is that propositional knowledge is not enough to give you either personal knowledge or procedural knowledge. Personal knowledge involves acquiring propositional knowledge in a certain way, and procedural knowledge may entail propositional knowledge, but the same propositional knowledge certainly does not entail procedural knowledge.
Whatever the connections between the various types of knowledge there may be, however, it is propositional knowledge that is in view in most epistemology.
The Tripartite Theory of Knowledge
http://www.theoryofknowledge.info/what-is-knowledge/the-tripartite-theory-of-knowledge/
There is a tradition that goes back as far as Plato that holds that three conditions must be satisfied in order for one to possess knowledge. This account, known as the tripartite theory of knowledge, analyses knowledge as justified true belief. The tripartite theory says that if you believe something, with justification, and it is true, then you know it; otherwise, you do not.
Belief
The first condition for knowledge, according to the tripartite theory, is belief. Unless one believes a thing, one cannot know it. Even if something is true, and one has excellent reasons for believing that it is true, one cannot know it without believing it.
Truth
The second condition for knowledge, according to the tripartite theory, is truth. If one knows a thing then it must be true. No matter how well justified or sincere a belief, if it is not true that it cannot constitute knowledge. If a long-held belief is discovered to be false, then one must concede that what was thought to be known was in fact not known. What is false cannot be known; knowledge must be knowledge of the truth.
Justification
The third condition for knowledge is justification. In order to know a thing, it is not enough to merely correctly believe it to be true; one must also have a good reason for doing so. Lucky guesses cannot constitute knowledge; we can only know what we have good reason to believe.
The tripartite theory of knowledge is intuitively very plausible. Since Edmund Gettier’s critique of it in the 60s, however, using thought-experiments now known as Gettier cases, it has been generally rejected. Nevertheless, it is still used as a working model by philosophers most of the time.
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Gettier Cases
http://www.theoryofknowledge.info/what-is-knowledge/the-tripartite-theory-of-knowledge/gettier-cases/
The tripartite theory of knowledge analyses knowledge as justified true belief. According to this analysis, if something is true, and we believe it to be true, and we are justified in believing it to be true, then we know it.
The tripartite theory, though it has been around since Plato, and though it is still widely used by many philosophers as a working model of knowledge, is false. This was shown to the satisfaction of most philosophers by Edmond Gettier, who developed what are now known as “Gettier cases”.
Gettier cases are cases in which the tripartite theory’s three conditions for knowledge are satisfied, i.e. in which a person does have a justified true belief, but in which there is no knowledge. The existence of such cases shows that there is something more to knowledge than justified true belief, and so that the tripartite theory of knowledge is false.
Suppose that two students, Mark and Sam, have taken a test. Mark is a straight A student, while Sam consistently fails any work he is set. Mark has attended the lessons in preparation for the test, while Sam has been absent due to illness. Mark revised hard for the test, while Sam stayed out all night at a party. Mark wrote furiously for the full duration of the test, while Sam wrote a few lines and then walked out in disgust. Mark says that the test went well, while Sam says that he didn’t even understand the question.
Reflecting on the test, and on a book that he has recently been reading, Sam forms the following belief: the student that will get the highest grade on the test shares a name with the author of The Adventures of Huckleberry Finn.” Sam clearly has excellent evidence for this belief, he is justified in believing it; he has excellent evidence that Mark will get the highest grade on the test, and can see from the cover of his copy of “The Adventures of Huckleberry Finn that it was written by Mark Twain. Furthermore, the belief is true; the student that will get the highest grade on the test does indeed share a name with the author of “The Adventures of Huckleberry Finn.” According to the tripartite theory of knowledge, therefore, Sam knows that the student that will get the highest grade on the test shares a name with the author of “The Adventures of Huckleberry Finn.”
Sam, however, does not know this. Mark, despite his excellent grades in the past, perfect attendance, hours of revision, furious writing, and confidence, failed the test. He did not appreciate the subtlety of the question, and so missed its point entirely. Sam, on the other hand, despite his previous poor grades, frequent absences, late night partying, and pessimism concerning his performance, did understand the question. In the few lines that he wrote he managed to scrape a passing grade. Sam, therefore, rather than Mark, got the highest grade on the test.
Unknown to Sam, though, he does share a name with the author of “The Adventures of Huckleberry Finn.” Its author, who used the pseudonym Mark Twain, was in fact called Samuel Clemens. Sam, therefore, who is the student who will get the highest grade on the test, does share a name with the author of Huckleberry Finn.
Although Sam clearly did have a justified true belief, he equally clearly did not have knowledge. His justification for his belief, far from helping him to discern the truth, threatened to lead him astray. The truth of his belief had nothing to with his reasons for holding it; it was nothing more than good luck that the belief that he formed was true.
This example, and other Gettier cases like it, show that it is possible to have justified true belief without having knowledge; the tripartite theory of knowledge, which holds that justified true belief and knowledge are precisely the same thing, is therefore false.
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Knowledge Without Belief?
http://www.theoryofknowledge.info/what-is-knowledge/the-tripartite-theory-of-knowledge/knowledge-without-belief/
According to the tripartite theory of knowledge, knowledge is justified true belief. One proposed counter-example to this theory is the case of the nervous student. This is supposedly a case of knowledge without belief, thus showing that it is possible to have knowledge without satisfying all three of the tripartite theory’s conditions for knowledge, that those conditions are not necessary conditions for knowledge.
The case of the nervous student is as follows: A student in a history class has been taught that the Battle of Hastings took place in 1066. The student, however, lacks confidence, and so when asked in a subsequent class when the Battle of Hastings occurred is convinced that he does not know. The date “1066” comes into his mind, but he does not give it any particular weight. However, absent any alternative ideas, this is the date that he gives in response to the question.
It seems that the student does know that the Battle of Hastings took place in 1066. He gave the correct answer to the question as to when it occurred, and he did so because he had been taught the correct date.
However, it also seems that the student does not believe that it occurred in 1066. If he were asked whether he believes that it occurred in 1066, he would dissent, and he of all people knows best what he believes and what he does not.
The nervous student thus appears to have knowledge without belief. The conditions for knowledge proposed by the tripartite theory therefore do not seem to be necessary; it seems to be possible to have knowledge without satisfying all three conditions.
Sources of Knowledge
http://www.theoryofknowledge.info/sources-of-knowledge/
Each of us possesses a great deal of knowledge. We know about ourselves; we know about the world around us; we know about abstract concepts and ideas. Philosophers have often wondered where this knowledge ultimately comes from.
Of course, we learn a lot of things from books, from the media, and from other people. To process information from these sources, however, we must already know many things: how to read, how to reason, who to trust. To learn these things requires yet more knowledge. What, then, is the most fundamental way of acquiring knowledge?
There are two competing traditions concerning the ultimate source of our knowledge: empiricism and rationalism.
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Empiricism
http://www.theoryofknowledge.info/sources-of-knowledge/empiricism/
Empiricism is the theory that experience is of primary importance in giving us knowledge of the world. Whatever we learn, according to empiricists, we learn through perception. Knowledge without experience, with the possible exception of trivial semantic and logical truths, is impossible.
Classical Empiricism
Classical empiricism is characterised by a rejection of innate, in-born knowledge or concepts. John Locke, well known as an empiricist, wrote of the mind being a tabula rasa, a “blank slate”, when we enter the world. At birth we know nothing; it is only subsequently that the mind is furnished with information by experience.
Radical Empiricism
In its most radical forms, empiricism holds that all of our knowledge is derived from the senses. This position leads naturally to the verificationist principle that the meaning of statements is inextrically tied to the experiences that would confirm them. According to this principle, it is only if it is possible to empirically test a claim that the claim has meaning. As all of our information comes from our senses, it is impossible for us to talk about that which we have not experienced. Statements that are not tied to our experiences are therefore meaningless.
This principle, which was associated with a now unpopular position called logical positivism, renders religious and ethical claims literally nonsensical. No observations could confirm religious or ethical claims, therefore those claims are meaningless. Radical empiricism thus requires the abandonment of religious and ethical discourse and belief.
Moderate Empiricism
More moderate empiricists, however, allow that there may be some cases in which the senses do not ground our knowledge, but hold that these are exceptions to a general rule. Truths such as “there are no four-sided triangles” and “7+5=12” need not be investigated in order to be known, but all significant, interesting knowledge, the empiricist claims, comes to us from experience. This more moderate empiricism strikes many as more plausible than its radical alternative.
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Rationalism
http://www.theoryofknowledge.info/sources-of-knowledge/rationalism/
Rationalism holds, in contrast to empiricism, that it is reason, not experience, that is most important for our acquisition of knowledge. There are three distinct types of knowledge that the rationalist might put forward as supporting his view and undermining that of the empiricist.
First, the rationalist might argue that we possess at least some innate knowledge. We are not born, as the empiricist John Locke thought, with minds like blanks slates onto which experience writes items of knowledge. Rather, even before we experience the world there are some things that we know. We at least possess some basic instincts; arguably, we also possess some innate concepts, such as a faculty for language.
Second, the rationalist might argue that there are some truths that, though not known innately, can be worked out independent of experience of the world. These might be truths of logic or mathematics, or ethical truths. We can know the law of the excluded middle, answers to sums, and the difference between right and wrong, without having to base that knowledge in experience.
Third, the rationalist might argue that there are some truths that, though grounded in part in experience, cannot be derived from experience alone. Aesthetic truths, and truths about causation, for instance, seem to many to be of this kind. Two people may observe the same object, yet reach contradictory views as to its beauty or ugliness. This shows that aesthetic qualities are not presented to us by our senses, but rather are overlaid onto experience by reason. Similarly, we do not observe causation, we merely see one event followed by another; it is the mind, not the world, that provides us with the idea that the former event causes the latter.
Theories of Perception
http://www.theoryofknowledge.info/theories-of-perception/
On a straightforward view, we directly perceive the world as it is. The way that things look, feel, smell, taste, and sound is the way that they are. We see colours, for example, because the world is coloured. This view of perception is called, somewhat dismissively, naive realism.
Plausibly, perception is a lot more complicated than this. Though things may appear to be coloured to us, our experiences of colour are merely representative of the surface properties of objects; the physical property of reflecting certain wavelengths of light and the colour red as we experience it are two quite different things.
This has led to representative realism, which suggests that perception is not the passive process that the naive realist suggests, that we do not simply receive information about the world through our senses. Rather, we are actively involved in perception, supplying much of the content of our experiences, and must bear this in mind if we are to know what the world is really like in itself.
More extreme than either naive or representative realism is idealism. Idealists, persuaded by the thought that we have direct access only to our experiences of the world, and not to the world itself, have questioned whether there is anything beyond our experiences. A more recent theory that bears some similarities to idealism has also been proposed: phenomenalism.
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Naive Realism
http://www.theoryofknowledge.info/theories-of-perception/naive-realism/
Naive realism is the common sense theory of perception. Most people, until they starting thinking philosophically, are naive realists. This theory is also known as “direct realism” or “common sense realism”.
Naive realism holds that the view of the world that we derive from our senses is to be taken at face value: there are objects out there in the world, and those objects have the properties that they appear to us to have. If I have an experience as of a large apple tree, then that’s because there’s a large apple tree in front of me. If the apples on the tree appear to me to be red, then that’s because there are objects in front of me, apples, that have the property redness; simple.
Plausible though naive realism may be, it has serious problems, among which is the problem of the variability of perception. The same object may appear differently to different people, or to the same person at different times. The apples may appear to be red in the daytime, but at dusk they are a shade of grey. If naive realism is to be taken seriously, and colours are out there in the world, then apples regularly change colour depending on how much light is around them. It is much more plausible, though, to think that the apples are the same as they ever were, that all that has changed is our experience of them.
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Representative Realism
http://www.theoryofknowledge.info/theories-of-perception/representative-realism/
According to representative realism, we do not perceive objects directly. Rather, objects cause us to have certain experiences, sense-data, and it is these to which we have direct access. Representative realism thus introduces a distinction, not present in naive realism, between our experiences of objects and the objects themselves. John Locke was a leading advocate of this theory.
Consider colour properties. There are two different ways of thinking about colour. The first is in scientific terms: colour is to with reflecting certain wavelengths of light. The second is in experiential terms: colour is a subjective experience that a normal observer has when they look at a coloured object.
Primary and Secondary Qualities
Representative realism holds that there are two completely different types of property, corresponding to this distinction.
First, there are primary qualities, which objects have independent of any observer. An object is square, or heavy, for instance, irrespective of whether anyone is perceiving it to be such. Shape and weight are therefore primary qualities.
Second, there are secondary qualities, which objects only have because they are perceived. Secondary qualities, like colour, are projected onto the world by perceivers. The apple isn’t really that shade of red, it just appears that way to me; I project redness onto the apple in the act of perceiving it. Colour, then, is a secondary quality.
We tend to use secondary qualities to represent primary qualities. Thus the red appearance of the apple, which is a secondary quality that I project onto it, represents the fact that it reflects certain wavelengths of light, which is a primary quality that it has irrespective of whether I am looking at it or not.
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Idealism
http://www.theoryofknowledge.info/theories-of-perception/idealism/
Idealism denies the existence of mind-independent objects. For the idealist, “to be is to be perceived”; objects are nothing more than our experiences of them.
The attraction of idealism is its economy. We don’t have direct access to the external world, it is generally agreed; all we can access directly are our experiences. Why, then, postulate the existence of anything beyond our experiences? The idealist refuses to do so, holding that our experiences don’t represent objects, but rather constitute them, that there is nothing beyond them.
For the idealist, then, objects only exist insofar as they are perceived. If I shut my eyes, then unless there is someone else perceiving the objects that surround me, those objects will cease to exist, at least until I reopen my eyes and perceive them once more.
Setting aside its initial implausibility, the main difficulty with this view is that it cannot explain the consistency of our experiences of the world. Why, when I reopen my eyes, do I see the same objects that I saw before? What causes me to perceive those objects rather than any others? Why, if two observers look in a single cupboard, and then compare what they saw, will both observers’ reports tally?
Berkeley, the most famous idealist, had both an answer to this problem and a way of avoiding the absurd suggestion that everytime I blink my study passes out of and back into existence in a fraction of a second: this answer is God.
God, according to Berkeley, is constantly perceiving everything. Though I may blink, and so stop perceiving my study, God continues to perceive it whether my eyes are open or shut. My study, therefore, never passes out of existence, for it is always perceived by God.
What is more, God explains the consistency in our perceptions. Though there may be no mind-independent objects causing our experiences, and so ensuring that our various experiences are mutually consistent, there is nevertheless something outside us causing our experiences and ensuring that they are consistent: God. God thus plays a central role in Berkeley’s idealism.
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Phenomenalism
http://www.theoryofknowledge.info/theories-of-perception/phenomenalism/
Phenomenalism is best thought of as a secular idealism. Like idealism, it holds (roughly) that objects are dependent upon our perceptions of them. Unlike idealism, however, it is not committed to the existence of a God who is constantly perceiving everything.
Idealism holds that objects exist only insofar as they are perceived. It therefore faces the dual problem of explaining what happens to objects when we cease to perceive them, and why different people’s experiences are consistent. To solve both of these problems, idealism invokes God.
Phenomenalism differs from idealism in that it holds that objects exist insofar either as they are perceived or as it is possible to perceive them. Phenomenalism is thus a weaker theory than idealism. Whereas idealists are committed to the idea that an object that is not perceived does not exist, phenomalists can allow that such objects exist insofar as it is possible to perceive them. They therefore have no need to invoke God to explain objects disappearing and reappearing when people cease and recommence perceiving them, as the idealist does.