Critical Thinking PHIL 2232
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l o Logicthe science of proper reasoning and the analysis of arguments o Argumentthe process of supporting a thesis called the conclusion with reasons called premises or assumptions 39 QjS t tqnent propositiona declarative sentenrethat is either an affirmation or a denia Will 0 An argument is a linguistic construction used to appeal to one s intellect in order to persuade that person to adopt or reject a certain belief gt o Conclusionthe statement that expresses the viewpoint that the argument is designed to defend 0 Therefore So Hence 0 PremisesAssumptionsstatements v 70 e d as evidence for the conclusion beiause for the reason that O J 2 M 2 0 Deductive argumentdesigned to support its thesis with total conclusiveness o Inductive argumentdesighed to support its thesis with enough evidence to make it only probably true ofPngbly o Wikely u gt L o Gil i o A valid deductive argument is one that guarantees that its conclusion is true so long as its premises are true 0 A valid deductive argument cannot have true assumptions and a false conclusion 39 of person is mortal o a kstgent is a person There ore every student is mortal o Inductive arguments are said to be either strong or weak oThe conclusion of a strong inductive argument can be false wen its premises are true F gt J L it Q 0 Truth Preservation and Structure A valid deductive argument has a truth preserving structure which is determined by the way its put together viz its form Classi cations For Deductive Arguments 0 Valid argument deductive argument that guarantees the truth of its conclusion when its premises are true 0 0 Sound argument deductive argument that i39bhvalid and cogent i 3 Ii i o All frogs are amphibians Some amphibians are not poisonous Hence no poisonous creatures are frogs a All ostriches are birds Some birds are not poisonous So some poisonous creatures arena ostriches o All ns are pink things All pink things are b astho all swans are birds Conditional Statement Hypothetical claim typically has the form If p then q Antecedent follows if and states a sufficient condition Consequent follows then and state the ssary condition L o Modus Ponens If p then q p Therefore q Example If it s pouring outside then it39s a mg riqg outside Ks raining 39 gt L a 6 H G o Modus Tollens If p then q Not q So not p Example If it s pouring outside then it s gufr in ng It39sjleaiQing quot739 9 it s et pguring W o Af rming the consequent an invalid inference pattern If p then q q Hence p Example If it s pouring outside then it s raining It s i i g Hence k b ouring outside O gt L o i Denying the antecedent an invalid inference pattern If p then q Not p Therefore not q 39 Ex pl If it s pouring outside then it s rai i not pouring outside There e it39s not raining O o Disjunction Statement that has the form Either p or q Example Either she is a doctor or a highly trained novice o Disjunctive Syllogism Either p or q Not p Therefore q c arq e Either you received an A for thegmhse or a B You did not receive a Nhecourse So you got an A LOGIC oAll the rules in logic are truthpreserving They are based on valid argument farms The Glove Argument Nil 0 Either OJ was framed or he is guilty of murder Premise o If OJ is guilty of murder then the bloody glove ts OJ Premise o If the bloody glove ts OJ then it is not tog small for his hand Premise 0 13 xlofw glove is too small for his hand Pre ise There re 0J was framed O DimctProof o F OJ was framed o G OJ is guilty of murder 0 B The bloody glove fits QJ s hand 0 S The bloody glove is too small for Gum s hand 39 Direct Proof 0 1 Either F or G Premise o 2 If G then B Premise o 3 If B then not S Premise o 4 S Premise o swisiot B 34 Modus Tollens 6 Bug 25 Modus Tollens I o 7 F pisjunctive Syllogism WW 0 Contradiction statement of the form quotp and not p o A contradiction cannot be true 0 The presence of a contradiction in an argument proof sequence is logical 39 d nce that at least one of its as Kpg39ls must be false LOGIC o Reductio Ad Absurdum reduction to an absurdity Also called proof by contradiction 0 Technique Introduce the contradictory logical opposite of the conclusion that want to establish and then derive a co ction Lit WPPN Either F or G Premise If G then B Premise If B then not S Premise S Premise Not F Assumption for reductio ad aburdum G 1 5 Disjunctive Syllogism 7 6 Modus Ponens a 7 Modus Ponens S an 0 S Contradiction from 4 and 8 a Some common assumptions 0 Law of Excluded Middle every statement has a de nite truthvalue it is either true or false 0 Law of noncontradiction contradictory or s 1 Ily opposite assertions cannot both Wire same time 39 Conditional Statement Hypothetical claim typically has the form If p then q Eg If it s pouring outside then it39s raining Antecedent follows if and states a sufficient condition Cquot e uent follows then and state the p mecssary condition If q can also be expressed as p t a lyi e13 V n O WW 0 Standard Contradiction statement of the form p and not p o A contradiction cannot be true 0 The presence of a contradiction in an argument or proof sequence is logical 39 dense that at least one of the as s is false Truth and Paradoxes 0 Truth is a characteristic of statements 0 Traditionally there are two main theories of the nature of truth o TheCorrespondence Theory a true statement is one that serves as an accurate copy faithful reproduction of I reality i TRUTH o Coherence theory of truth the truth of a statement is determined by how well it coheres fits or sticks together with other statements in a comprehensive belief system a With the correspondence theory statements are compared to reality a With thecoherence theory statements are t I measuredonly against other statements PARADOX o Paradox an argument or piece of reasoning that engenders a contradiction and where we find the contradiction amusing or even alarming because it seems to be supported by beliefs that we find completely acceptable 0 Antinomy a paradox that serves to discredit or seriously challenge a longestablished and Widelx accepted principle of reasoning Introducing the Biconditional o P if and only if Q If P then Q and if Q then P a if and only if not is logically equivalent to P and not o The paradox of the barber Consider a man who lives in a certain village and who shaves all and only those men in the village who never shave themselves Does he ever shave himself o If yes then he never shaves himself o If Lno then he does shave himself 39 o Hen c39ekhe shaves himself if and only if he never sh aVes himself Therefore he both shaves himselfyand never shaves himself p PAMDOXES o Grellirlg s Paradox o An adjective is autological just in case it is self descriptive Examples short polysyllabic English and so on a The following are examples of adjectives that are etautological German long and mo stllabi39cf u I Such adjectives are said to be heterologlcal Grelling s Paradox o Is the adjective heterological heterological o If yes then it is autological in which case it is true of itself and therefore it is not heterological o If no then it fails to be selfdescriptive and hence it is heterological after all 0 80a heterological is heterological if and only if it is nOtxheterological o There fgrehthe adjective heterological is true of I itself and itx is not true of itself Traditional Characteristics of Truth 0 Aristotle s de nition of truth To say of what is that it is not or of what is not that it is is false but to say of what is that it is and of what is not that it is not is true Metaphysics A o The TEquivalence S is true if and only if Ex ample The sentence Some swans afr blaellt is true if and only if some swans I are b lack The Paradox of the Liar a The statement on this particular PowerPoint slide is false The Paradox of the Liar 0 Let S represent the statement on the previous slide 0 S is either true or it isn t o If S is true then it is also false since it says of itself that it isn t true o If S is false then it follows that what it says of itself namely that it isn t true is false Hence it isfals ethat S is false which entails that S is true flt is not the case that S is false means the same as S is true p 18 Paradox oi the Liar q 80 S is true if and only if S is net true a Therefore S is both true and false S nalize Version 0 The expression yields a false statement when appended to its own quotatien yields a false statement when appended to its own quotation 39 Ordered ntuples a An ordered ntuple is a class of classes whose elements obey a certain ordering condition ltagt ltagtltbgt gt ab o ltebgt ltabgtltcdgt gt aC A bd o lt b gtltd3 gt gt adb A I x Rum Warmox q A class set is any abstract collectien or combination at things a Examples the class set of all men who were Presidents of the United States during the nineteenth century q39l1 class set of all positive integers 9 Th set of red apples that are tlfin my refrigerator O Classes 0 Consider the class of red things Anything is a member of this class if and only if it is red 0 The class of elephants has all but only elephants as its members and so on Classes again a Some classes have other classes as members a Examples The class of positive integers is a member of the class of all classes of numbers 0 Q szys a member of O 5 01 2 q So ecrzltlcs admire only one another Classes 0 Most classes are not members of themselves 0 Examples the class of red things is not a member of itself since it isn t red 0 The class of elephants is not an elephant so it is not a member of itself a Theclass of positive integers is not itself a posi integer so it is not a member of itself quot p Gottlob Frege 18481925 Grundgesetze der Arithmetik Basic Laws of Arithmetic Vol 1 1893 Vol 1903 a System of justification for mathematical truths and to tie all branches of mathematics to a common core so a Twstem of the Grundgesetze logically guaralgttees that any articulable condition deter lines a class 9 The Crisis in Mathematics Bertrand Russell 18721970 a Author of Principia Mathematica 11910 11913 a In 1901 Russell discovered a serious problem in Frege s system The Russell Class 0 Consider the class of all and only those classes that are not members of themselves 0 Let R stand for this class 5 o C is a member of R if and only if C is not a member of itself Ema fs Paradox 0 Either R is a member of R or it isn t a If R is a member of R then it is not a member of R a If R is not a member of R then it is a member of R a Hence R is a member of R if and only if it iSQndtxe member of R q SoFN bpth a member of itself and it isn t x Russell s solution a The theory of types 1908 the universe of classes is stratified or has a hierarchal structure 0 Ernst Zermelo proposed his own system in 1908 as well 0 Involves intuitively plausible axioms for generating defining classes Axioms of unconditional class existence are needed I to pdmue the pump Another system a The axioms of Zermelo s system imply a restriction on the size of classes Classes that are too big so to speak don t exist a John von Neumann s system dates back tof1 925 It makes a distinction between classesthat are members of classes sets I andthLose that are not proper classes Other paradoxes o Geog Cantor 18451918 father of class theory 0 A cardinal number is the measure of the size of a class 0 Cantor s paradox there is a greatest cardinal number and there is no limit to how large a Class can be o Orginal number specifies the length of a series 0 ialiorti paradox there is no end to how long a ser es can be but there is a greatest ordinal numbem 39 Russell 0 Principles of Mathematics 1903 a The ontology was unrestrained every word referred to something a The referent of a proper name is a thing a The referent of predicates and other expressions are concepts qr Igir nited the term existence to things but re ckonecl things liberally including tempoan quotinstants and points of empty space Russell 0 Beyond eXIstence are other things such as numbers the Homeric Gods unicorns multidimensional spaces and even impossible objects such as round squares and integers greater than seven but less than three o the present King of France a thiw nged horse captured by Bellerophon I g the seqQandso Russell 0 Alexius Meinong 118531920 0 Russell s theory of descriptions 119051 0 Paraphrasis de ning a term by providing equivalents of all desired sentences containing the term 0 Reference to purportedly existing fictitious fovla Jiects can be simulated in meaningful without the need to actually postulatesoch objects Russell q The Philosophy at Logical Atemismj quot 11918 a Russell new postulates entities called tacts as well as what he called particular existing things qt vrti ular existing things can be named K e Fas sfrted or denied 3 Russell 0 Russell always thought of cognitive meaning in terms of the notion of reference For most of his philosophical career meaning is nothing more than reference 0 Facts serve the role of being the referents offcornplete declarative sentences 0 Factsare just as real as particular existing I thingsfi USSS o For Russell the objective world the world of both facts and particular existing things is constructed out of completely simple irreducible metaphysical entities called logical atoms Russell 0 Russell describes logical atoms as those ultimate simples out of which the world is built that have a kind of reality not belonging to anything else Simples are of an infinite number of sorts There areparticulars and qualities and relations ofgya rious orders a whole hierarchy e P 27o f Arguments 0 Conclusion What it is claimed to be supported by the presented evidence 0 Conclusion indicators therefore wherefore thus consequently we may infer that accordingly it must be that for thistreason entails that hence it follows thatfi mplies that as a result and so on 39 39 Arguments o Premises Statements claimed to be evidence for the conclusion 0 Premises indicators since as indicated by because for given that seeing that for the reason that inasmuch as owing to anldthe like 0 Iri nee The reasoning process expressed by an argument 39 Answers to Homework assignment 1 o Exercises 14 Part I o 2 Valid unsound false premises false conclusion 0 3 Valid sound true premise true conclusion 0 5 Invalid unsound false premise true conclusion 0 6T Valid unsound false premise true concussion r9 Validgunsound false premise true conclusion Answers to homework assignment 1 o Exercises 14 Part I o 9 Valid sound true premises true conclusion 0 11 Invalid unsound false premise false conclusion 0 12 Valid sound true premises true conclusion o 1x lalid unsound one false premise true c nK ion 0 15 ound true premise true conclusion 0 Answers to homework assignment 1 o Exercises 14 Ill 0 2 inductive weak 0 5 deductive valid 0 8 deductive invalid o 11 inductive weak o 1f1n dgluctive valid o 17eductlve valid 2 20 deductive invalid 39 3 inductive strong 6 inductive strong 9 inductive strong 12 deductive invalid 15 inductive strong 18 deductive valid Proving Invalidity o Substitution instance An argument or statement that has the same form as a given argument form or statement form 0 All wombats are marsupials o All marsupials are warm blooded o 39lfl neeg all wombats are warm blooded o AWWEHM All M are WB Hence all W are W 39 Principle of Universal Form a Any argument that has the same form as a valid argument is valid also a Any argument that has the same form as an invalid argument is likewise invalidl s x Counterexample Method 0 Since some employees are not social climbers and all Vice preSIdents are employees we may conclude that some Vice presidents are not social climbers 0 Some E are not S All V are E Therefore some V are not S o Emammals Screature smaller than an elephant Vvampire bats 0 sq e ammals arenot creatures smaller than elep nts1 All vampire bats are mammals The some vampire bats are not creatures smaller anelephants Exercises to homework assignment 1 0 Exercise 15 Part I e 2 No C are E Some P are not C Therefore some E are not P o No cats are dogs Some animals are not cats Therefore some dogs are not animals o 310 P are M All P are R Thus no M are R e Notsare dogs All cats are animals Thus no d sare animals 39 Exercises for homework assignment 1 o 5 Some P are W No Ware T Therefore No P are T 0 Some positive integers are odd numbers No odd numbers are even numbers Therefore no positive integers are even numbers 0 6 All S are T All S are M TherefOre all M are T Avgpositive integers are numbers greater than 2 ro All positive integers are integers The A ore all integers are numbers greater than zero O Exercises for homework assignment 1 o 8 Some T are S Some S are U Hence some T are U 0 Some turtles are reptiles Some reptiles are alligators Therefore some turtles are alligators o 9 All Aare G Some Aare I Hence some I are not G s o All Quares are subjects of geometry Some sare geometric shapes Hence some eom g i c shapes are not subjects of geometry P Part II 0 1i If it s pouring then it s raining It s not pouring Therefore it s not raining o 2 If it s pouring then it s raining It s raining So it s pouring o If Lassie is a dog then Lassie is an animal If Lassie is a cat then Lassie is ansanimal So if Lassie is a dog then Lassi esisa cat 39 Part II a 4 If Roger is a human male then either he is a frog er a human If Roger is frog then he is an amphibian Hence if Roger is a human male then he is an amphibian q 5 All humans who are adult females are wemen So all humans are women a 6 gtome fruits are purple Some fruits are lemons Sp some fruits are purple femens39 Part II a 7 All felines with fur are either mammals or dogs 80 all cats are dogs a 8 All animals that are cats are felines that are mammals So all animals are mammals g dogs are either mammals or fish 310m dggs are mammals So some degs are fishT Part II a 1lO All cats that are mammals are either dogs are animals All cats are animals 80 all animals are dons Varieties of Meaning 0 Ordinary language is used to fulfill a myriad of purposes question asking story telling telling lies answering guessing formation of hypotheses insulting joke telling flirting direction giving singing issuing commands greeting someone and soon K g 39 0 Cognitive meaning information conveyed by an expression 0 Emotive meaning feeling expressed or invoked by an expression 0 value claim a judgment that something is good or badright or wrong better or worse more impogantor less important than some other thing Value claims are said to be evaluative 39 Some Defects of Cognitive Meaning 0 Vagueness condition whereby an expression allows for borderline cases in which it is very difficult to determine whether it has been applied correctly or not 0 Ambiguity a condition whereby an exipression can be interpreted as having more than one distinct meaning in a I certaintcontext Varieties of Terms 0 A term is any expression that functions as a noun or a pronoun 0 Proper names Napoleon St Louis Pakistan Hilary Clinton Scott and so on 0 Common nouns amphibian intoxication red house uncle corn and so on 0 Descriptive phrases first President of the United Statesxthe author of Waverly the present King of France officers in the French Army the class of redthings the pizza in my fridge and so on 39 Remus continued 0 Individual constants often numerals functions letters and other special symbols of mathematics 0 Variables x y z tx v 099 n W a An expression is used when it is applied in such a way that it is intended to have a cognitive meaning a An expression is mentioned when it is referred to by an expression 0 Tile word red is not polysyllabic o Theiadjective polysyllabic has five syllaloie sr 39 9 UseMention again The first line of Gray s Elegy is the sentence the The curfew tells the knell of parting day The first line of Grey s Elegy refers to the sentence The curfew tells the knell of peurrt39ng day j x 39 Types of coma Meaning o intensional meaning intensionconnotationsense the qualities or attributes that a term expresses or implicitly desc bes o The intensional meaning sense of a term is its conceptual content ie the information that it expresses o N in ensional meaning of a term is its criterion Types of Cognitive Meaning 0 Extensional Meaning extensiQndenotatianreferent the thing or class of things referred to picked out by a term Emmpiz of taertnsion vs mansion o inventor o Intension collection of connoted attributes or expressed concepts clever intuitive creative imaginative adept at mathematics and the like 0 mension the class of individuals referred tcbe yxthe expression inventor l Thomas Ed isgn Alexander Graham Bell Samuel F Morse Wright brothers and so on mm of utu and mum o The current President of the United States 0 Intensional meaning sense the present head of state and head of government of the United States chief of the executive branch of the US government has the newer to create a cabinet of the g ernment and to grant pardons elected into cagc etin 2008 and so can 39 Exampie of extensions and intensions o The current President of the United States 0 Extensional meaning referent Barack Obama or the class whose sole member is Barack Obama 0 Unicorn 0 u mioinal meaning equine creature has a h o nwhite o Exten ionainmeaning the empty class or no extensional meaning Definitions 0 A definition is a group of words that assigns a meaning to a word or group of words 0 De niendum the word or group of words that is supposed to be defined 0 De njens the word or group of words that downedle i n in g K gt f De nitions 0 Lexical de nition a definition used to report the meaning that a word already has in a language a intractable means not easily governed obstinate unruly not disposed to be taught 39 39 I 39 WWII o Stipulative de nition a definition that assigns a meaning to a word for the first time The defined expression definiendum may be a brand new term or this process may involve giving a new meaning to an old term This type of definition often has the purpose of replacing a complex expression with a simpler one o a reognobile means a vehicle that is normally drivien On the ground but that has the capability of flying through the air to avoid traffic congestion f Mirmm o Precising de niton reduces the vagueness of an expression by giving a word a more restricted range of application o assault means for legal purposes an intentional and unprivileged act resulting in theapp rehension of an immediate harmful I or offensi Ve contact Bc n39i ons 0 Theoretical de nition assigns a meaning to a word by suggesting a theory that gives a certain characterization to the entities denoted by the definiendum o spund means a compression wave in air ogrgs ome other elastic medium having a fre qt en cy ranging for humans from 20 to I 2000 inibrations per second De ni ons o Persuasive de nition encourages a favorable or unfavorable attitude to what is described by the definiendum o psychiatry means the accidental and presumably scientific combining of modern L medicine With psychology that promises relief to thousands of poor desperate souls who suffer the pains Ofemotional disorder 39 De nitional techniques 0 Extensional techniques for defining terms assigns a meaning to a word by specifying its extension The extension of a term is the class of things of which the term is true Extensional techniques 0 Ostension defining by pointing a desk means this thing and that as your pointing at several of them 75 j t p Extensional techniques 0 Enumerative de nition defines by naming some of the members of the extension of the definiendum a actress means a person such as Nicole Natalie Portman Sharon Stone an soo n EX39IENSIONAL TECHNIQUES 0 De nition by subclass defines by naming subclasses of the term s extension 0 Tree means an oak pine elm spruce maple and the like i De nitional Techniques Again 0 lntensional de nition defines by indicating the qualities or characteristics associated with the definiendum o Synonymous definition defines by using a single word that is synonymous with the definiendum in u I o physrcian means doctor Intensional techniques 0 Etymological de nition defines by indicating the word s history in both its own language and other languages a license is derived from the Latin word libere which means to be permitted R lntensional techniques 0 Operational de nition defines by specifying certain experimental procedures that determine the application of the word o A subject has brain activity if and only if an39eflectroencephalograph shows oscillations when attached to the subject s I head lntensional de nitions 0 De nition by genus and difference defines by specifying a broad class of related things genus and by specifying certain characteristics differences that enable us to mark out interesting subclasses in the genus a bachelor means an adult male who is unmarried adult male is the genus term and unmarried is the difference term L Homework 0 Exercise 23 Part I pp 95 96 0 Exercise 24 Part I pp 103104 FALLACIES o A fallacy is a defect in an argument that consists in something other than the possession of false premises 0 Non sequiturit does not follow an invalid deductive argument or a weak inductive argument Formal Fallacies q A formal fallacy is a defect that pertains to the form of an argument q Examples are af rming the consequent and denying the antecedent Informal Fallacies o Informal fallacies can be detected only by examining the content of the argument 0 Examples The Brooklyn Brid e is made of atoms Atoms are invisible herefore the Brooklyn Bridge is invisible o A chess player is a person So a bad chess player is a bad person 0 There is no doubt that Ral h is a chocolate addictstor the reason that e s constantly round the clb chin desperate need of a serious choc Rate fix O Informal Fallacies of Relevance a This type of fallacy is committed when the argument has premises that are not logically relevant to the conclusion but the premises are psychologically relevant Informal Fallacies of Relevance 0 Appeal to Force Argumentum ad baculumAppeal to the Stick arguer poses a conclusion to another person and tells that person either implicitly or explicitly that some harm will come to himher if helshe does not accept the conclusion you welcome the opportunity to join our c e force for think of all the money you39ll roken windows overturned trucks and da an d merchandise if you don t join Informal Fallacies of Relevance 0 Appeal to Pity Argumentum ad Misericordiam arguer attempts to support the conclusion by invoking pity from the reader or listener o Surely architect Norris is not responsible for the collapse of the Central Bank Tower Norris has had nothing but trouble lately His daughter d with a child molester his son committed nd his alcoholic wife recently left for with his retirement savings Ji ide Las Inform Fa acics of Rackvanct 0 Appeal to the peoplemasses argumentum ad populum appeals to desires enjoyed by many people to make the conclusion look acceptable 0 Bandwagon Variety o 9 coarse you want to take Critical Th i gwhile you39re at GSU Even if you don39t edjt everybody loves it O MW 4340 of quotKeithnee 0 Appeal to vanity version of ad populum o GSU students are the smartest and the best looking So GSU or bust 0 Appeal to snobbery version of ad populum o A RollsRoyce is certainly not for everyone If qualify as one of the select few this dEtinrgdished classic may be seen and driven at Britillvlotor Cars Ltd 9 39nforma Faiiacigs o Argument against the person Argumentum ad hominem arguer criticizes the person rather than the argument 0 Ad hominem abusive rejects by using verbal abuse 0 Professor Pearson s arguments in favor of the theory of evolution should be discounted P ea r sw is a cocainesnorting sex pervert and acc rxdin g to some reports a member of the com m LKr iisTtxparty Informal Fallacies of Relevance 0 Ad hominem circumstantial rejects by referring to psychologicalsocial circumstances that have predisposed the arguer to take up a certain view q Well of course Aristotle holds that a society is necessary for leariinrgxproper morals He was always a mem ler oif the upper crust of his society Informal Fallacies of Relevance 0 Tu quoque version of the ad hominem fallacy arguer attempts to discredit the arguer s position by making himher appear guilty of hypocrisy or arguing in bad faith 0 Dr Morrison has argued that smoking is responsible for the majority of health problems in this country and that every smoker should quit Qniozrtgnately39 however we must consign Dr Moqsonjs argument to the trash bin Only yestergay lsaw none other than Dr Morrison hiimrsel smdking a cigar P Informal Fallacies of Relevance 0 Accident fallacy committed when a general rule is applied to a Specific case that it does not fit 0 The First Amendment to the Constitution prevents the government from interfering with the exercise of religion The liturgical practice of the Religion of Internal Enlightenment involves ugh sacri ce Therefore it would be wrong c s h n f aegovernment to interfere with this religious pra T O Informal Fallacies of Relevance o Straw Man mistake made when an arguer distorts or misrepresents a position to make it easier to attack attacks the distorted version and then concludes that the opponent s real argument has been demolished Example TV commentator Larry Kudlow argues that government should get off the back of the American businessperson Surely Kudlow wants to abolish government altogether But without government there wo39t JId be no defense no judicial system no Social Security wand no health and safety regulations None of us w an s toforgo these benefits Hence we can see that Ku lowsargument is absurd P Informal Fallacies of Relevance 0 Missing the Point Ignoratio Elenchl Premises of the argument support a particular conclusion but a different and related conclusion is drawn 0 Example Abuse of the welfare system is very common these days So our only alternative is to abolish the system altogether o Eghabs it would be much more reasonable to revamp the system in certain ways in order to minimize the number of cheaters 39 Informal Fallacies of Relevance 0 Red Herring arguer diverts the attention of reader or listener by changing the subject to a different but somewhat related one 0 Example Environmentalists are continually harping about the dangers of nuclear power Unfortunately electricity is dangerous no matter where it comes from Every year hundreds of p ople re electrocuted by accident Since most Naccidents are caused by carelessness I they d e avoided if people would just rciseg ater caution D X D O Informal Fallacies of Weak Induction o This type of mistake in reasoning occurs when the connection between the premises and the conclusion is not strong enough to support the conclusion Informal Fallacies of Weak Induction 0 Appeal to Unquali ed Authority Argumentum ad Verecundiam to support a thesis the arguer cites the authority or testimony of another person who lacks credibility 0 Radio entertainer Rush Limbaugh claims that there is not a shred of evidence to prove that nicotine is addictive or that cigarettes cause emphysema lung cancer or any other disease GivgdLimbaugh s apparent expertise in medical science we can only conclude that what he says about nicotine and cigarettes is true 0 Fallacies of Weak induction Appeal to Ignorance Argumentum ad lgnorantiam Premises of an argument state that nothing has been proved one way or the other about something and the conclusion then makes a definite assertion about that thing General Form Nobody has ever shown that S is true 80 S must be false Or nobody has ever proven that S is false so S must be true quot Exam ple No one has conclusively shown that America s nuclear power plants constitute a danger to people living in theirimrhediate vicinity Therefore it is unquesti pnably safe to continue to build nuclear power plants near large metropolitan centers I Fallacies of Weak Induction o Hasty Generalization Converse Accident This mistakes occurs when there is a reasonable likelihood that the sample is not representative of the group 0 General characterisitc speci c case does not support general rule o The Daily News carried an article this morning aboUtthree local teenagers who were arrested ori caarge s of drug possession You know teena ers39these days are nothing but a bunch of junkies 1 39 Fallacies of Weak Induction 0 False Cause post hoc ergo propter hoc connection between premises and conclusion depends on a supposed causeandeffect relation that probably does not exist 0 Example There are more churches in New York City than in any other city in the nation and mg iregrimes are committed in New York City tha anywhere else So if we are to eliminate crimeyye must abolish the churches 39 Fallacies of Weak Induction o Slippery Slope variety of the false cause fallacy It occurs vvhen the conclusion of an argument rests on an alleged chain reaction and there is not sufficient evidence to believe that the chain reaction will actually take place 0 Example We don39t dare let the animal rights activists get their foot in the door If they sell us on the idea that dogs cats and dolphins have rights next it will be ichgcke oand cows That means no more barbecue oh en r prime rib Next it will be worms and insects I lead to the decimation of our agricultural Ti starvation of the human race will follow close be ind O Fallacies of Weak Induction a Weak Analogy 0 An argument from analogy is one in which the conclusion depends on the existence of an analogy or a relevant similarity between two things or circumstances qugample of an argument from analogy teq s 2009 Porsche is a great handling ca Therefore Christina39s 2009 Porsche is pro blya great handling car Weak Analogy continued 0 The general form of an argument from analogy Thing A has characteristics x y and 2 Thing B has characteristics x and y Therefore B probably has characteristic 2 also Weak Analogy continued a The fallacy of weak analogy is committed when the analogy or similarity is not strong enough to support the conclusion 0 Example Harper s new car is bright blue has leather upholstery and gets great gas mileage Jackson s car is also bright blue arnfdrhas leather upholstery Therefore Ja KsO n s car probably gets good gas mileage L Informal Fallacies of Ambiguity 0 An informal fallacy of ambiguity arises due to some form of ambiguity in the premises or the conclusion Fallacies of Ambiguity o Equivocation the conclusion of the argument depends on a word or an expression being used implicitly or explicitly in two different senses 0 Examples A law can be repealed by the legislative authority But Newton s theory of gravitational attraction is based on a law So v vt n39s theory of gravitational attraction can be re le by the legislative authority Ala ouse is an animal So a large mouse is an en urm0us animal Fallacies of Ambiguity o Amphiboly this mistake occurs when the arguer misinterprets a relatively ambiguous statement and then draws a conclusion based on this faulty interpretation 0 Example the tour guide said that standing in Greenwich Village the Empire State Building cofuldbe seen It follows that the Empire State in Greenwich Village a X L i Fallacies of Grammatical Analogy o A fallacy of grammatical analogy is committed by arguments that are grammatically analogous or structurally similar to good arguments but the similarity is only superficial Fallacies of grammatical analogy 0 Composition conclusion of the argument depends on a quality being mistakenly transferred from the parts to the whole 0 Example Maria likes anchovies She also likeschocolate ice cream So it is certain I th at sh ewould like a chocolate sundae topded ith anchovies Fallacies of grammatical analogy 0 Division quality is mistakenly transferred from the whole to its parts 0 Example This jigsaw puzzle when put together is circular in shape Therefore each of its pieces is circular in shape 0 isa nonpoisonous compound He its components sodium and chlori a are nonpoisonous O Fallacies of Presumption 0 These fallacies arrive not because the premises are logically irrelevant to the conclusion or because the premises provide insufficient evidence to believe the conclusion instead they occur when the premises strongly presume what they are intended to prove k z E 52 L p Palaces of Presumption o Begging the question petitio principii quotrequest for the source circular reasoning q The conclusion of the argument is restated in some way in the premises so unless the readerlistener already accepts theconclusion a key premise of the ent will be regarded as unacceptable 39 Begging the question 0 Examples 0 I know the Bible is divinely inspired because the Bible itself says so in Ch 3 of II Timothy 0 Only the fittest of organisms survive because any organism that survives must be among the fittest o Iij elthat there is good reason to believe that ghosts exist because I am convinced that they are real F Palaces of Presumption 0 Complex Question two or more questions are asked in the guise of a single question and a single answer is expected to be given 0 Examples When will you consider not stealing from your coworkers q A ryo ustill beating your spouse Fallacies of Presumption 0 False Dichotomy committed when two alternatives are presented as mutually exclusive but there is a third option a Example 9 Wife to husband Either you put me before all of your other family members or you dbn tlove me p Fallacies of Presumption or The Fallac of Su ressed Evidence 0 The requirement of true premises involves the agreement that whenever possible the arguer should not ignore a vital piece of evidence that serves to overturn the stated evidence and thereby support a different conclusion The fallacy of suppressed evidence is committed when this requirement is violated 0 Example Most dogs are friendly and pose no threat to peoplewho pet them So it would be completely safe to pe tae little dog that is approaching us now The unstated fact being that the little dog is agitated and foamingat the mouth 39 Answers to 32Part o appeal to pity q 239 argument against the person 0 red herring 4 accident a 5 appeal to the masses ad populum o 6 argument against the person abusive arptpieal to force 8 straw man 1 9 issing the point ment against the person you too O Answers to 32Part I 11 No fallacy 12 appeal to the people 13 red herring 14 appeal to pity 15 accident 16 argument against person 17quot argument against the person abusive 18 No fallacy 19 straw man 20 appeal to force 21 red herring 22 appeal to the people 23 No fallacy because Ma well has not really presented an argument 39 lo 2 4 argument against the person you too aways point 9 115 Exercises 33Part I 1 Hasty generalization 2 weak analogy 3 appeal to unqualified authority 4 slippery slope 5 No Fallacy 6 false cause Appeal to ignorance 8 no fallacy 9 hasty generalization 10 Appeal to unquali ed authority The senator s statement is a case of politically motivated hysteria gtmdi39i ering gcTra a 1 1 12 Slippery slope 13 a alogy 14 appeal to ignorance 0 false cause
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