Theory of knowledge


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  • A branch of philosophy
  • Plato holds that in a sense there are two separate worlds or realms; or, to put the point a little more tamely, that there are two very different kinds of things, ordinary physical objects and Forms. Here are some of the main differences between the two.
  • In this article, and in epistemology in general, the kind of knowledge usually discussed is propositional knowledge, also known as "knowledge-that" as opposed to "knowledge-how." For example: in mathematics, it is known that 2 + 2 = 4, but there is also knowing how to add two numbers. Many (but not all) philosophers therefore think there is an important distinction between "knowing that" and "knowing how", with epistemology primarily interested in the former. A proposition is a sentence expressing something true or false. In philosophy, particularly in logic, a proposition is identified ontologically as an idea, concept, or abstraction whose token instances are patterns of symbols, marks, sounds, or strings of words
  • The relationship between belief and knowledge is that a belief is knowledge if the belief is true, and if the believer has a justification (reasonable and necessarily plausible assertions/evidence/guidance) for believing it is true.A false belief is not considered to be knowledge, even if it is sincere. A sincere believer in the flat earth theory does not know that the Earth is spherical. Similarly, a truth that nobody believes is not knowledge, because in order to be knowledge, there must be some person who knows it.
  • Belief as a psychological theoryMainstream psychology and related disciplines have traditionally treated belief as if it were the simplest form of mental representation and therefore one of the building blocks of conscious thought. Philosophers have tended to be more abstract in their analysis and much of the work examining the viability of the belief concept stems from philosophical analysis.The concept of belief presumes a subject (the believer) and an object of belief (the proposition). So, like other propositional attitudes, belief implies the existence of mental states and intentionality, both of which are hotly debated topics in the philosophy of mind whose foundations and relation to brain states are still controversial.Beliefs are sometimes divided into core beliefs (those you may be actively thinking about) and dispositional beliefs (those you may ascribe to but have never previously thought about). For example, if asked 'do you believe tigers wear pink pajamas ?' a person might answer that they do not, despite the fact they may never have thought about this situation before.[4]That a belief is a mental state has been seen, by some, as contentious. While some philosophers have argued that beliefs are represented in the mind as sentence-like constructs others have gone as far as arguing that there is no consistent or coherent mental representation that underlies our common use of the belief concept and that it is therefore obsolete and should be rejected.This has important implications for understanding the neuropsychology and neuroscience of belief. If the concept of belief is incoherent or ultimately indefensible then any attempt to find the underlying neural processes that support it will fail. If the concept of belief does turn out to be useful, then this goal should (in principle) be achievable.Philosopher Lynne Rudder Baker has outlined four main contemporary approaches to belief in her controversial book Saving Belief[5]Our common-sense understanding of belief is correct - Sometimes called the ‘mental sentence theory’, in this conception, beliefs exist as coherent entities and the way we talk about them in everyday life is a valid basis for scientific endeavour. Jerry Fodor is one of the principal defenders of this point of view.Our common-sense understanding of belief may not be entirely correct, but it is close enough to make some useful predictions - This view argues that we will eventually reject the idea of belief as we use it now, but that there may be a correlation between what we take to be a belief when someone says 'I believe that snow is white' and how a future theory of psychology will explain this behaviour. Most notably philosopher Stephen Stich has argued for this particular understanding of belief.Our common-sense understanding of belief is entirely wrong and will be completely superseded by a radically different theory that will have no use for the concept of belief as we know it - Known as eliminativism, this view, (most notably proposed by Paul and Patricia Churchland), argues that the concept of belief is like obsolete theories of times past such as the four humours theory of medicine, or the phlogiston theory of combustion. In these cases science hasn’t provided us with a more detailed account of these theories, but completely rejected them as valid scientific concepts to be replaced by entirely different accounts. The Churchlands argue that our common-sense concept of belief is similar, in that as we discover more about neuroscience and the brain, the inevitable conclusion will be to reject the belief hypothesis in its entirety.Our common-sense understanding of belief is entirely wrong; however, treating people, animals and even computers as if they had beliefs, is often a successful strategy - The major proponents of this view, Daniel Dennett and Lynne Rudder Baker, are both eliminativists in that they believe that beliefs are not a scientifically valid concept, but they don’t go as far as rejecting the concept of belief as a predictive device. Dennett gives the example of playing a computer at chess. While few people would agree that the computer held beliefs, treating the computer as if it did (e.g. that the computer believes that taking the opposition’s queen will give it a considerable advantage) is likely to be a successful and predictive strategy. In this understanding of belief, named by Dennett the intentional stance, belief based explanations of mind and behaviour are at a different level of explanation and are not reducible to those based on fundamental neuroscience although both may be explanatory at their own level.How beliefs are formedPsychologists study belief formation and the relationship between beliefs and actions. Beliefs form in a variety of ways.We tend to internalize the beliefs of the people around us during childhood. Albert Einstein is often quoted as having said that "Common sense is the collection of prejudices acquired by age eighteen." Political beliefs depend most strongly on the political beliefs most common in the community where we live.[6] Most individuals believe the religion they were taught in childhood.[7]People may adopt the beliefs of a charismatic leader, even if those beliefs fly in the face of all previous beliefs, and produce actions that are clearly not in their own self-interest.[8] Is belief voluntary? Rational individuals need to reconcile their direct reality with any said belief; therefore, if belief is not present or possible, it reflects the fact that contradictions were necessarily overcome using cognitive dissonance.The primary thrust of the advertising industry is that repetition forms beliefs, as do associations of beliefs with images of sex, love, and other strong positive emotions.[9]Physical trauma, especially to the head, can radically alter a person's beliefs.[10]However, even educated people, well aware of the process by which beliefs form, still strongly cling to their beliefs, and act on those beliefs even against their own self-interest.Belief-inTo "believe in" someone or something is a distinct concept from "believe-that". There are two types of belief-in:[11]Commendatory - an expression of confidence in a person or entity, as in, "I believe in his abililty to do the job".Existential claim - to claim belief in the existence of an entity or phenomenon with the implied need to justify its claim to existence. It is often used when the entity is not real, or its existence is in doubt. "He believes in witches and ghosts" or "many children believe in fairies" are typical examples.[12]Delusional beliefsDelusions are defined as beliefs in psychiatric diagnostic criteria (for example in the Diagnostic and Statistical Manual of Mental Disorders). Psychiatrist and historian G. E. Berrios has challenged the view that delusions are genuine beliefs and instead labels them as "empty speech acts", where affected persons are motivated to express false or bizarre belief statements due to an underlying psychological disturbance. However, the majority of mental health professionals and researchers treat delusions as if they were genuine beliefs.In Lewis Carroll's Through the Looking-Glass, the White Queen says, "Why, sometimes I've believed as many as six impossible things before breakfast." This is often quoted in mockery of the common ability of people to entertain beliefs contrary to fact.
  • Whether somebody's belief is true is not a prerequisite for someone to believe it. On the other hand, if something is actually known, then it categorically cannot be false. For example, a person believes that a particular bridge is safe enough to support them, and attempts to cross it; unfortunately, the bridge collapses under their weight. It could be said that they believed that the bridge was safe, but that this belief was mistaken. It would not be accurate to say that they knew that the bridge was safe, because plainly it was not. By contrast, if the bridge actually supported their weight then they might be justified in subsequently holding that he knew the bridge had been safe enough for his passage, at least at that particular time. For something to count as knowledge, it must actually be true. There is a sense that makes us feel that the truth should command our belief.The Aristotelian definition of truth states:"To say of something which is that it is not, or to say of something which is not that it is, is false. However, to say of something which is that it is, or of something which is not that it is not, is true."
  • JustificationIn Plato's dialogue Theaetetus, Socrates considers a number of theories as to what knowledge is, the last being that knowledge is true belief that has been "given an account of" — meaning explained or defined in some way. According to the theory that knowledge is justified true belief, in order to know that a given proposition is true, one must not only believe the relevant true proposition, but one must also have a good reason for doing so. One implication of this would be that no one would gain knowledge just by believing something that happened to be true. For example, an ill person with no medical training, but a generally optimistic attitude, might believe that they will recover from their illness quickly. Nevertheless, even if this belief turned out to be true, the patient would not have known that they would get well since their belief lacked justification. The definition of knowledge as justified true belief was widely accepted until the 1960s. At this time, a paper written by the American philosopher Edmund Gettier provoked major widespread discussion. See theories of justification for other views on the idea.A. Hume's argument that induction cannot be rationally justified. Two versions of this argument:1. The first version: Induction presupposes the Principle of the Uniformity of Nature, the idea that the unobserved parts of the universe (those parts in the future, or a long time ago, or a long way away, for instance) are more or less similar to the observed parts. But there is no way to justify this principle except by induction itself.2. The second version abandoned the Principle of the Uniformity of Nature, and was expressed in terms of inference rules instead. There are two problems with inductive inference rules.a. It is difficult (impossible?) to formulate a precise rule of inductive inference. Deductive inference rules, by contrast, are easy. For instance: if you have the premise that if p then q, and the premise that p, then you may infer that q. What would a corresponding inductive inference rule look like? Perhaps something like this: If you have the premise that all observed A's have been B's, then you may infer that all A's are B's. More generally, from the premise that n% of observed A's have been B's, infer that n% of all A's are B's.But clearly that rule is not satisfactory. Some instances of the rule seem OK: for instance, from the premise that all observed emeralds have been green, it seems reasonable to infer that all emeralds are green. However, other instance of the formula do not fare so well. For instance (Nelson Goodman's "new riddle of induction"), from the premise that all observed emeralds have been grue, it does not seem acceptable to infer that all emeralds are grue.b. Suppose we somehow managed to construct an inductive inference rule that seemed intuitively to be acceptable. How could we show that it is reliable? In the case of deductive inference rules, we can show (by using truth tables, for instance) that the rules can never lead us from true premises to a false conclusion, and hence are legitimate deductive inference rules. In the case of an inductive inference rule, we would like to show that the rule will usually lead from true premises to a true conclusion. But Hume's circularity worry seems to be a serious problem here. It seems that to infer that induction is usually reliable, we would need to make an inference something like this:most observed uses of induction have been reliablethereforemost uses of induction are reliable. . . which is an instance of the inductive pattern, and so amounts to using induction to justify our use of induction.2. One response to these problems with the justification of induction is to argue that they presuppose a foundationalist conception of justification. On the foundationalist view, beliefs come in distinct layers. On the bottom, there are indubitable beliefs, for example about one's own existence and mental states. On the next level up, we have observational beliefs about the world. A level higher than that, we have beliefs about unobserved entities. The foundationalist view is that every belief on any given level must be justified entirely on the basis of beliefs at the next lower level (so that ultimately everything is justified on the basis of indubitable beliefs).Sober suggests that foundationalism is mistaken. Perhaps we need a more coherentist conception of justification. Instead of saying that we are justified in believing p only if we can derive p from lower-level beliefs, perhaps we should say something like this: I am justified in believing that p unless I have some concrete reason to doubt it. (A concrete reason for doubt could be observational evidence that conflicts with p, or it could be a conflict between p and other things I believe.) Notice that the evil genius does not count as a concrete reason to doubt my beliefs unless and until I have some reason to believe that there actually is an evil genius.3. Another response to the worries about induction may be to suggest that induction as it is usually described is not in fact an inference rule we actually use. We should notice three things about our inferences from observed to unobserved phenomena:a. sometimes many positive instances are not enough to lead us to believe a general proposition. (The turkey's induction, the water balloon induction, the iron-is-always-a-solid induction, etc.)b. sometimes a single positive instance is enough. (I wonder whether the red area on the stovetop feels nice. I touch it and burn myself. I do not need to do several more trials to convince myself that it will always burn me if I touch it.)c. even when we do believe a generalization on the basis of observation of positive instances, it does not seem to be the mere repetition of positive instances that explains our confidence in the generalization.These observations may lead us to wonder whether many inferences that could be thought of as inductive are not better described as abductive instead. For instance, I notice that all the emeralds I have observed have been green. What is the best explanation of this fact? I may consider various possible explanations: all emeralds are green, all emeralds are grue, I've observed a highly biased sample and in fact a small percentage of emeralds is green, and so on. It seems that, rather than just mechanically extend my observations to a broader sample, I in fact try to determine which of these various possibilities is the best explanation of my observations.An interesting and related twist on the issue is the view of Karl Popper. Popper also held that induction is not an inference procedure we actually use. However, he would also have rejected the idea that we use abduction. Popper held that the only form of reasoning we use in deciding what to believe is deductive reasoning. We can refute a theory by deductive reasoning if we encounter an observation that is incompatible with what the theory predicts: T -> E, but not E, therefore not T is a valid deductive argument form. Popper thought that we never have reason to hold that a particular theory is true; the best we can say is that we have not yet refuted it. In his view, science is not about establishing the truth of the right theory, but about trying as hard as we can to refute the ones that aren't true. All we can say about the ones that survive the testing is that we don't yet have any reason to think them false. Popper defends this view in "Conjectural Knowledge: My Solution of the Problem of Induction," chapter 1 of his book Objective Knowledge.)
  • The Gettier problemMain article: Gettier problemEdmund Gettier is remembered for his 1963 argument which called into question the theory of knowledge that had been dominant among philosophers for thousands of years.[4] In a few pages, Gettier argued that there are situations in which one's belief may be justified and true, yet fail to count as knowledge. That is, Gettier contended that while justified belief in a true proposition is necessary for that proposition to be known, it is not sufficient. As in the diagram above, a true proposition can be believed by an individual (purple region) but still not fall within the "knowledge" category (yellow region).According to Gettier, there are certain circumstances in which one does not have knowledge, even when all of the above conditions are met. Gettier proposed two thought experiments, which have come to be known as "Gettier cases," as counterexamples to the classical account of knowledge. One of the cases involves two men, Smith and Jones, who are awaiting the results of their applications for the same job. Each man has ten coins in his pocket. Smith has excellent reasons to believe that Jones will get the job and, furthermore, knows that Jones has ten coins in his pocket (he recently counted them). From this Smith infers, "the man who will get the job has ten coins in his pocket." However, Smith is unaware that he also has ten coins in his own pocket. Furthermore, Smith, not Jones, is going to get the job. While Smith has strong evidence to believe that Jones will get the job, he is wrong. Smith has a justified true belief that a man with ten coins in his pocket will get the job; however, according to Gettier, Smith does not know that a man with ten coins in his pocket will get the job, because Smith's belief is "...true by virtue of the number of coins in Jones's pocket, while Smith does not know how many coins are in Smith's pocket, and bases his belief...on a count of the coins in Jones's pocket, whom he falsely believes to be the man who will get the job." (see [4] p. 122.) These cases fail to be knowledge because the subject's belief is justified, but only happens to be true by virtue of luck (in other words,he made the correct choice (in this case predicting an outcome) for the wrong reasons).It is far from clear that Gettier was the first to present this challenge to the justified-true-belief triumvirate. Some scholars attribute an extremely similar idea to Bertrand Russell.[citation needed]1. Gettier examples. Although the belief that the person who will get the job has ten coins in his pocket is justified and true, it does not seem to be a reliable indicator (in the sense of our third version of condition (3)). The process by which the belief was arrived at (namely deduction from a false premise) could just as easily have led to a false belief as to a true one.2. The stopped clock. Again, although in this case my belief based on the clock reading turns out to be true, it is not a reliable indicator of the time. I could just as easily have passed the clock a little earlier or later, in which case my belief would have been false. (This does raise the issue of how broad the circumstances we need to consider are, though. Sober points out that to some extent this will be relative to the context in which we ask the question. But it seems that there will be very few contexts in which the relevant circumstances include the exact time at which one forms a belief.)3. The lottery. My belief that I won't win is justified and true. However, again, it is not a reliable indicator of the truth in the relevant sense. A belief is a reliable indicator of a fact only if, given my circumstances, I could only acquire the belief if it were true. But in the lottery case it is entirely possible (though not likely) that I could acquire the belief even though it were false. After all, the person who actually wins the lottery had equally good reason to believe that he or she would not win.[edit] Responses to GettierThe responses to Gettier have been varied. Usually, they have involved substantive attempts to provide a definition of knowledge different from the classical one, either by recasting knowledge as justified true belief with some additional fourth condition, or as something else altogether.[edit] Infallibilism, indefeasibilityIn one response to Gettier, the American philosopher Richard Kirkham has argued that the only definition of knowledge that could ever be immune to all counterexamples is the infallibilist one.[5] To qualify as an item of knowledge, so the theory goes, a belief must not only be true and justified, the justification of the belief must necessitate its truth. In other words, the justification for the belief must be infallible. (See Fallibilism, below, for more information.)Yet another possible candidate for the fourth condition of knowledge is indefeasibility. Defeasibility theory maintains that there should be no overriding or defeating truths for the reasons that justify one's belief. For example, suppose that person S believes he saw Tom Grabit steal a book from the library and uses this to justify the claim that Tom Grabit stole a book from the library. A possible defeater or overriding proposition for such a claim could be a true proposition like, "Tom Grabit's identical twin Sam is currently in the same town as Tom." So long as no defeaters of one's justification exist, a subject would be epistemically justified.The Indian philosopher B K Matilal has drawn on the Navya-Nyayafallibilism tradition to respond to the Gettier problem. Nyaya theory distinguishes between know p and know that one knows p - these are different events, with different causal conditions. The second level is a sort of implicit inference that usually follows immediately the episode of knowing p (knowledge simpliciter). The Gettier case is analyzed by referring to a view of Gangesha (13th c.), who takes any true belief to be knowledge; thus a true belief acquired through a wrong route may just be regarded as knowledge simpliciter on this view. The question of justification arises only at the second level, when one considers the knowledgehood of the acquired belief. Initially, there is lack of uncertainty, so it becomes a true belief. But at the very next moment, when the hearer is about to embark upon the venture of knowing whether he knows p, doubts may arise. "If, in some Gettier-like cases, I am wrong in my inference about the knowledgehood of the given occurrent belief (for the evidence may be pseudo-evidence), then I am mistaken about the truth of my belief -- and this is in accord with Nyayafallibilism: not all knowledge-claims can be sustained."[6]ReliabilismMain article: ReliabilismReliabilism is a theory that suggests a belief is justified (or otherwise supported in such a way as to count towards knowledge) only if it is produced by processes that typically yield a sufficiently high ratio of true to false beliefs. In other words, this theory states that a true belief counts as knowledge only if it is produced by a reliable belief-forming process.Reliabilism has been challenged by Gettier cases. Another argument that challenges reliabilism, like the Gettier cases (although it was not presented in the same short article as the Gettier cases), is the case of Henry and the barn façades. In the thought experiment, a man, Henry, is driving along and sees a number of buildings that resemble barns. Based on his perception of one of these, he concludes that he has just seen barns. While he has seen one, and the perception he based his belief on was of a real barn, all the other barn-like buildings he saw were façades. Theoretically, Henry doesn't know that he has seen a barn, despite both his belief that he has seen one being true and his belief being formed on the basis of a reliable process (i.e. his vision), since he only acquired his true belief by accident.[7]
  • (the only change is to the third condition. We could regard this either as a replacement condition or as an explication of what it is to be justified. We could call this the CTB account, for Certain True Belief.)Descartes's increasingly radical skeptical arguments in Meditation I seem designed to show that it is possible that I am mistaken about almost everything I believe. If I recognize that it is possible for me to be mistaken, then I cannot be certain that I am correct. So the arguments of Meditation I seem to show that I do not know anything except perhaps that I exist and what my current experiences are.Of course, Descartes tries to overcome these skeptical doubts later in the Meditations, via his proof of God's existence in Meditation III. But most readers find the skeptical arguments more convincing than the proof of God's existence, so we seem to be left with the worry that if knowledge requires certainty, then we can know hardly anything.4. The evil genius. If Descartes' arguments that God exists and isn't a deceiver are not successful, then it appears that, according to the CTB, I cannot know (for example) that there is a computer monitor in front of me. This is because it's not certain (indubitable) that there's a monitor in front of me, since an evil genius could feed me monitor-like experiences even if there wasn't a monitor there.What about the RTB? We need to distinguish two cases. (1) There is an evil genius. In this case, my belief that there's a monitor in front of me is not a reliable indicator (even if there is in fact a monitor in front of me), because it could be false just as easily as true. In that case, I don't know that there is a monitor in front of me. (2) There is no evil genius (or other weird sceptical possibility). In that case, in the circumstances I'm actually in, my belief that there's a monitor in front of me could only be caused by . . . a monitor in front of me. So it's a reliable indicator, so I know that there's a monitor in front of me.I can't be certain, of course, that I'm in situation (2) rather than situation (1). But if, as I believe, I am in fact in situation 2, then I do know that there's a monitor in front of me. The mere possibility of an evil genius isn't enough to prevent me from knowing: only an actual evil genius could do that!
  • Notice that the new condition 3 is an objective, not subjective condition: that is, it says something about the circumstances S is actually in, not (just) about S's subjective mental state.Notice also that it follows from this definition that one could know that p without knowing that one knows that p. That is, I could believe p, p could be true, and I could be in circumstances in which that belief could only be caused only by the fact that p, even though I did not in fact know that I was in such circumstances.If there is no evil demon, and no other systematically deceptive feature of my circumstances relevant to my belief that p, then arguably if p is an observational belief (I see a hand in front of me, the car is green, etc.), then it is such that I could only come to believe it on the basis of the fact it represents.So it looks like the RTB gives the answers that seem right in the cases that the JTB account had trouble with. What about the kind of case that gave the CTB trouble?
  • Other responsesThe American philosopher Robert Nozick has offered the following definition of knowledge:S knows that P if and only if:P;S believes that P;if P were false, S would not believe that P;if P is true, S will believe that P.[8]Nozick believed that the third subjunctive condition served to address cases of the sort described by Gettier. Nozick further claims this condition addresses a case of the sort described by D. M. Armstrong:[9] A father believes his son innocent of committing a particular crime, both because of faith in his son and (now) because he has seen presented in the courtroom a conclusive demonstration of his son's innocence. His belief via the method of the courtroom satisfies the four subjunctive conditions, but his faith-based belief does not. If his son were guilty, he would still believe him innocent, on the basis of faith in his son; this would violate the third subjunctive condition.The British philosopher Simon Blackburn has criticized this formulation by suggesting that we do not want to accept as knowledge beliefs which, while they "track the truth" (as Nozick's account requires), are not held for appropriate reasons. He says that "we do not want to award the title of knowing something to someone who is only meeting the conditions through a defect, flaw, or failure, compared with someone else who is not meeting the conditions.".[citation needed] In addition to this, externalist accounts of knowledge, like Nozick's, are often forced to reject closure in cases where it is intuitively valid.Timothy Williamson has advanced a theory of knowledge according to which knowledge is not justified true belief plus some extra condition(s). In his book Knowledge and its Limits, Williamson argues that the concept of knowledge cannot be analyzed into a set of other concepts—instead, it is sui generis. Thus, though knowledge requires justification, truth, and belief, the word "knowledge" can't be, according to Williamson's theory, accurately regarded as simply shorthand for "justified true belief."
  • Externalism and internalismMain article: Internalism and externalismPart of the debate over the nature of knowledge is a debate between epistemological externalists on the one hand, and epistemological internalists on the other. Externalists think that factors deemed "external", meaning outside of the psychological states of those who gain knowledge, can be conditions of knowledge. For example, an externalist response to the Gettier problem is to say that, in order for a justified, true belief to count as knowledge, it must be caused, in the right sort of way, by relevant facts. Such causation, to the extent that it is "outside" the mind, would count as an external, knowledge-yielding condition. Internalists, contrariwise, claim that all knowledge-yielding conditions are within the psychological states of those who gain knowledge.René Descartes, prominent philosopher and supporter of internalism wrote that, since the only method by which we perceive the external world is through our senses, and that, since the senses are not infallible, we should not consider our concept of knowledge to be infallible. The only way to find anything that could be described as "infallibly true," he advocates, would be to pretend that an omnipotent, deceitful being is tampering with one's perception of the universe, and that the logical thing to do is to question anything that involves the senses. "Cogito ergo sum" (I think, therefore I am) is commonly associated with Descartes' theory, because he postulated that the only thing that he could not logically bring himself to doubt is his own existence: "I do not exist" is a contradiction in terms; the act of saying that one does not exist assumes that someone must be making the statement in the first place. Though Descartes could doubt his senses, his body and the world around him, he could not deny his own existence, because he was able to doubt and must exist in order to do so. Even if some "evil genius" were to be deceiving him, he would have to exist in order to be deceived. However from this Descartes did not go as far as to define what he was. This was pointed out by the materialist philosopher Pierre Gassendi (1592–1655) who accused Descartes of saying that he was "not this and not that," while never saying what exactly was existing. One could argue that this is not an edifying question, because it doesn't matter what exactly exists, it only matters that it does indeed exist.
  • A priori and a posteriori knowledgeThe nature of this distinction has been disputed by various philosophers; however, the terms may be roughly defined as follows:A priori knowledge is knowledge that is known independently of experience (that is, it is non-empirical, or arrived at beforehand).A posteriori knowledge is knowledge that is known by experience (that is, it is empirical, or arrived at afterward).To borrow from Jerry Fodor (2004), take, for example, the proposition expressed by the sentence, "George V reigned from 1910 to 1936." This is something (if true) that one must come to know a posteriori, because it expresses an empirical fact unknowable by reason alone. By contrast, consider the proposition, "If George V reigned at all, then he reigned for at least a day." This is something that one knows a priori, because it expresses a statement that one can derive by reason alone.The phrases "a priori" and "a posteriori" are Latin for "from what comes before" and "from what comes later" (or, less literally, "before experience" and "after experience"). An early philosophical use of what might be considered a notion of a priori knowledge (though not called by that name) is Plato's theory of recollection, related in the dialogue Meno (380 B.C.), according to which something like a priori knowledge is knowledge inherent, intrinsic in the human mind.Eighteenth-century German philosopher Immanuel Kant (1781) advocated a blend of rationalist and empiricist theories. Kant states, "although all our knowledge begins with experience, it does not follow that it arises from experience"[2] According to Kant, a priori knowledge is transcendental, or based on the form of all possible experience, while a posteriori knowledge is empirical, based on the content of experience.
  • Some propositions are such that we appear to be justified in believing them just so far as we understand their meaning. For example, consider, "My father's brother is my uncle." We seem to be justified in believing it to be true by virtue of our knowledge of what its terms mean. Philosophers call such propositions "analytic." Synthetic propositions, on the other hand, have distinct subjects and predicates. An example of a synthetic proposition would be, "My father's brother has black hair." Kant held that all mathematical propositions are synthetic.The American philosopher W. V. O. Quine, in his "Two Dogmas of Empiricism," famously challenged the distinction, arguing that the two have a blurry boundary.Conceptual containmentThe philosopher Immanuel Kant was the first to use the terms "analytic" and "synthetic" to divide propositions into types. Kant introduces the analytic/synthetic distinction in the Introduction to the Critique of Pure Reason (1781/1998, A6-7/B10-11). There, he restricts his attention to affirmative subject-predicate judgments, and defines "analytic proposition" and "synthetic proposition" as follows:analytic proposition: a proposition whose predicate concept is contained in its subject conceptsynthetic proposition: a proposition whose predicate concept is not contained in its subject conceptExamples of analytic propositions, on Kant's definition, include:"All bachelors are unmarried.""All triangles have three sides."Kant's own example is:"All bodies are extended," i.e. take up space. (A7/B11)Each of these is an affirmative subject-predicate judgment, and in each, the predicate concept is contained with the subject concept. The concept "bachelor" contains the concept "unmarried"; the concept "unmarried" is part of the definition of the concept "bachelor." Likewise for "triangle" and "has three sides," and so on.Examples of synthetic propositions, on Kant's definition, include:"All bachelors are unhappy.""All creatures with hearts have kidneys."Kant's own example is:"All bodies are heavy," (A7/B11)As with the examples of analytic propositions, each of these is an affirmative subject-predicate judgment. However, in none of these cases does the subject concept contain the predicate concept. The concept "bachelor" does not contain the concept "unhappy"; "unhappy" is not a part of the definition of "bachelor." The same is true for "creatures with hearts" and "have kidneys" - even if every creature with a heart also has kidneys, the concept "creature with a heart" does not contain the concept "has kidneys."Kant's version and the a priori/ a posteriori distinctionIn the Introduction to the Critique of Pure Reason, Kant contrasts his distinction between analytic and synthetic propositions with another distinction, the distinction between a priori and a posteriori propositions. He defines these terms as follows:a priori proposition: a proposition whose justification does not rely upon experiencea posteriori proposition: a proposition whose justification does rely upon experienceExamples of a priori propositions include:"All bachelors are unmarried.""7 + 5 = 12."The justification of these propositions does not depend upon experience: one does not need to consult experience in order to determine whether all bachelors are unmarried, or whether 7 + 5 = 12. (Of course, as Kant would have granted, experience is required in order to obtain the concepts "bachelor," "unmarried," "7," "+," and so forth. However, the a priori / a posteriori distinction as employed by Kant here does not refer to the origins of the concepts, but to the justification of the propositions. Once we have the concepts, experience is no longer necessary.)Examples of a posteriori propositions, on the other hand, include:"All bachelors are unhappy.""Tables exist."Both of these propositions are a posteriori: any justification of them would require one to rely upon one's experience.The analytic/synthetic distinction and the a priori/a posteriori distinction together yield four types of propositions:analytic a priorisynthetic a priorianalytic a posteriorisynthetic a posterioriKant thought the third type is self-contradictory, so he discusses only three types as components of his epistemological framework. However, Stephen Palmquist treats the analytic a posteriori not only as a valid epistemological classification, but as the most important of the four for philosophy.[1]
  • EmpiricismMain article: EmpiricismIn philosophy, empiricism is generally a theory of knowledge emphasizing the role of experience, especially experience based on perceptual observations by the five senses. Certain forms treat all knowledge as empirical,[citation needed] while some regard disciplines such as mathematics and logic as exceptions.[citation needed][edit] RationalismMain article: RationalismRationalists believe that knowledge is primarily (at least in some areas) acquired by a priori processes or is innate—for example, in the form of concepts not derived from experience. The relevant theoretical processes often go by the name "intuition".[citation needed] The relevant theoretical concepts may purportedly be part of the structure of the human mind (as in Kant's theory of transcendental idealism), or they may be said to exist independently of the mind (as in Plato's theory of Forms).The extent to which this innate human knowledge is emphasized over experience as a means to acquire knowledge varies from rationalist to rationalist. Some hold that knowledge of any kind can only be gained a priori,[citation needed] while others claim that some knowledge can also be gained a posteriori.[citation needed] Consequently, the borderline between rationalist epistemologies and others can be vague.[edit] ConstructivismMain article: Constructivist epistemologyConstructivism is a view in philosophy according to which all knowledge is "constructed" in as much as it is contingent on convention, human perception, and social experience.[citation needed] Constructivism proposes new definitions for knowledge and truth that form a new paradigm, based on inter-subjectivity instead of the classical objectivity, and on viability instead of truth. Piagetian constructivism, however, believes in objectivity—constructs can be validated through experimentation. The constructivist point of view is pragmatic; as Vico said: "The norm of the truth is to have made it."It originated in sociology under the term "social constructionism" and has been given the name "constructivism" when referring to philosophical epistemology, though "constructionism" and "constructivism" are often used interchangeably.[citation needed] Constructivism has also emerged in the field of International Relations, where the writings of Alexander Wendt are popular. Describing the characteristic nature of International reality marked by 'anarchy' he says, "Anarchy is what states make of it."
  • According to this argument, any proposition requires a justification. However, any justification itself requires support, since nothing is true “just because”. This means that any proposition whatsoever can be endlessly (infinitely) questioned, like a child who asks "why?" over and over againStructureAssuming that knowledge is justified true belief. Then:Suppose that P is some piece of knowledge. Then P is a justified true belief.The only thing that can justify P is another statement – let's call it P1; so P1 justifies P.But if P1 is to be a satisfactory justification for P, then we must know that P1.But for P1 to be known, it must also be a justified true belief.That justification will be another statement - let's call it P2; so P2 justifies P1.But if P2 is to be a satisfactory justification for P1, then we must know that P2But for P2 to count as knowledge, it must itself be a justified true belief.That justification will in turn be another statement - let's call it P3; so P3 justifies P2.and so on, ad infinitum.
  • Response to the regress problemMany epistemologists studying justification have attempted to argue for various types of chains of reasoning that canescape the regress problem.InfinitismIt is not impossible for an infinite justificatory series to exist. This position is known as "infinitism." Infinitiststypically take the infinite series to be merely potential, in the sense that an individual may have indefinitely manyreasons available to him, without having consciously thought through all of these reasons when the need arises. Thisposition is motivated in part by the desire to avoid what is seen as the arbitrariness and circularity of its chiefcompetitors, foundationalism and coherentism. In mathematics, an infinite series will often converge - (this is thebasis of calculus) - one can therefore have an infinite series of logical arguments and analyze it for a convergent (ornon-convergent) solution.FoundationalismFoundationalists respond to the regress problem by claiming that some beliefs that support other beliefs do notthemselves require justification by other beliefs. Sometimes, these beliefs, labeled "foundational," are characterizedas beliefs of whose truth one is directly aware, or as beliefs that are self-justifying, or as beliefs that are infallible.According to one particularly permissive form of foundationalism, a belief may count as foundational, in the sensethat it may be presumed true until defeating evidence appears, as long as the belief seems to its believer to be true.Others have argued that a belief is justified if it is based on perception or certain a priori considerations.The chief criticism of foundationalism is that it allegedly leads to the arbitrary or unjustified acceptance of certainbeliefs.[11]CoherentismAnother response to the regress problem is coherentism, which is the rejection of the assumption that the regressproceeds according to a pattern of linear justification. To avoid the charge of circularity, coherentists hold that anindividual belief is justified circularly by the way it fits together (coheres) with the rest of the belief system of whichit is a part. This theory has the advantage of avoiding the infinite regress without claiming special, possibly arbitrarystatus for some particular class of beliefs. Yet, since a system can be coherent while also being wrong, coherentistsface the difficulty in ensuring that the whole system corresponds to reality.Epistemology 9FoundherentismThere is also a position known as "foundherentism". Susan Haack is the philosopher who conceived it, and it ismeant to be a unification of foundationalism and coherentism. One component of this theory is what is called the"analogy of the crossword puzzle." Whereas, say, infinists regard the regress of reasons as "shaped" like a singleline, Susan Haack has argued that it is more like a crossword puzzle, with multiple lines mutually supporting eachother.[12
  • Theory of knowledge

    1. 1. Theory of knowledge (tok)<br />Epistemology<br />
    2. 2. Philosophy<br />Philosophy is the science of the logical foundation of all knowledge<br />It is the first logical science<br />Philosophy is the highest generalization which scientific research suggest.<br />It consist of great unifying truth, the science of sciences.<br />
    3. 3. philosophy<br />Philosophy is:     (a) the attempt to acquire knowledge     (b) by rational means    (c) about topics that do not seem amenable to empirical investigation. <br />Condition <br />(a) distinguishes philosophy from creative disciplines such as literature or music. <br />(b) distinguishes philosophy from mysticism and some varieties of religion. <br />(c) distinguishes philosophy from the empirical sciences.<br />
    4. 4. Theory of knowledge<br />What is knowledge?<br />What are the types of knowledge?<br />How do we acquire knowledge?<br />What do we know?<br />How do we know what we know?<br />
    5. 5.
    6. 6. Types of knowledge<br />Propositional - What <br />Procedural - How<br />A proposition is a sentence expressing something true or false<br />
    7. 7. What is knowledge?<br />Knowledge is a“JustifiedTrue Belief” (JTB)<br /> Plato<br />S knows that p if and only if:(1) S believes that p(2) p is true(3) S is justified in believing that P<br />S = Subject<br />P = Proposition<br />
    8. 8. Belief<br />Belief is the psychological state in which an individual holds a proposition or premise to be true.[1]<br />1.Schwitzgebel, Eric (2006), "Belief", in Zalta, Edward, The Stanford Encyclopedia of Philosophy, Stanford, CA: The Metaphysics Research Lab,, retrieved 2008-09-19<br />
    9. 9. Truth<br />"To say of something which is that it is not, or to say of something which is not that it is, is false. However, to say of something which is that it is, or of something which is not that it is not, is true."<br />Aristotle<br />
    10. 10. Justification<br />To know that a given proposition is true<br />believe the relevant true proposition<br />have a good reason for doing so.<br />
    11. 11. The Gettier problem<br />“There are situations in which one's belief may be justified and true, yet fail to count as knowledge.”<br />
    12. 12. the Certain True Belief (CTB)<br />S knows that p if and only if:(1) S believes that p(2) p is true(3') S is absolutely certain that p<br />A problem: it seems to lead to skepticism about knowledge, the view that we can know little or nothing.<br />
    13. 13. the Reliable True Belief (RTB)<br />S knows that p if and only if(1) S believes that p(2) p is true(3'') S's belief that p is a reliable indicator that p: in the circumstances S is actually in, S's belief that p can be caused only by p.<br />
    14. 14. Knowledge and skepticism<br />S knows that P if and only if:<br />P;<br />S believes that P;<br />if P were false, S would not believe that P;<br />if P is true, S will believe that P<br />Robert Nozick (1981). Philosophical Explanations. Harvard University Press. ISBN0674664485  Philosophical ExplanationsChapter 3 "Knowledge and Skepticism" I. Knowledge Conditions for Knowledge p. 172-178.<br />
    15. 15. Externalism and internalism<br />Externalists: <br />the factors deemed "external", meaning outside of the psychological states of those who gain knowledge, can be conditions of knowledge<br />Internalists: <br />since the only method by which we perceive the external world is through our senses, and that, since the senses are not infallible<br />we should not consider our concept of knowledge to be infallible. <br />
    16. 16. How do we acquire knowledge?<br />A priori and a posteriori knowledge<br />Analytic/synthetic distinction<br />Specific theories of knowledge acquisition <br />Empiricism<br />Rationalism<br />Constructivism<br />The regress problem <br />Response to the regress problem<br />Infinitism<br />Foundationalism<br />Coherentism<br />Foundherentism<br />
    17. 17. A priori and a posteriori<br />A priori knowledge is knowledge that is known independently of experience <br />eg "George V reigned from 1910 to 1936." <br />A posteriori knowledge is knowledge that is known by experience <br />"If George V reigned at all, then he reigned for at least a day." <br />
    18. 18. Analytic/synthetic proposition<br />Analytic propositions are those which are true simply by virtue of their meaning.<br />"All bachelors are unmarried." <br />Synthetic propositions, on the other hand, have distinct subjects and predicates. <br />"All triangles have three sides.“ <br />
    19. 19. theories of knowledge acquisition<br />Empericism: that knowledge arises from sense experience<br />Rationalism: that knowledge is primarily acquired by a prioriprocesses or is innate<br />Constructivism: proposes new definitions for knowledge and truth that form a new paradigm, based on inter-subjectivity instead of the classical objectivity, and on viability instead of truth.<br />
    20. 20. The regress problem <br />Assuming that knowledge is justified true belief. Then:<br />Suppose that P is some piece of knowledge. Then P is a justified true belief.<br />The only thing that can justify P is another statement – let's call it P1; so P1 justifies P.<br />But if P1 is to be a satisfactory justification for P, then we must know that P1.<br />But for P1 to be known, it must also be a justified true belief.<br />That justification will be another statement - let's call it P2; so P2 justifies P1.<br />But if P2 is to be a satisfactory justification for P1, then we must know that P2<br />But for P2 to count as knowledge, it must itself be a justified true belief.<br />That justification will in turn be another statement - let's call it P3; so P3 justifies P2.<br />and so on, ad infinitum.<br />
    21. 21. Response to the regress problem<br />Infinitism: It is not impossible for an infinite justificatory series to exist<br />Foundationalism: that some beliefs that support other beliefs do not themselves require justification by other beliefs<br />Coherentism: that an individual belief is justified circularly by the way it fits together (coheres) with the rest of the belief system of which it is a part<br />Foundherentism: it is meant to be a unification of foundationalism and coherentism<br />
    22. 22. Perception<br />Basic kind of Perception<br />Theory of Perception<br />Phenomenalism<br />Perception and Senses<br />Problem of Perceptual knowledge<br />Indirect Realism<br />Idealism<br />Direct Realism<br />
    23. 23. Memory<br />
    24. 24. Reason<br />
    25. 25. testimony<br />
    26. 26. consciousness<br />
    27. 27. skepticism<br />