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12 fallacies-091211092734-phpapp01 12 fallacies-091211092734-phpapp01 Presentation Transcript

  • LOGIC Fallacies
  • Fallacies A fallacy is derived from the Latin word “fallo”, which means “I deceive”. It is a deceptive argument that seems to be conclusive but is actually not conclusive. Either its sequence seems to be valid but is actually invalid, or else its premise seems to be true but is actually false. An appearance of validity and truth is essential to a fallacy, for it would deceive no one unless it at least seemed to be valid or true. An intended fallacy is called “Sophism”. It gets this name because it was a favorite device of the ancient Greek sophists, who claimed to be able to prove either side of any question.
  • The term “fallacy” is sometimes applied to ambiguous statements thatare not actually parts of an argument. The reason for this is that theymight be understood in a sense in which they are not true and thus bean occasion of deception.Cause of Fallacies Many fallacies arise from the matter of inference rather from defective form and might consequently seem to lie outside the scope of logic. Since the time of Aristotle, treatises on logic have always included a discussion of fallacies.
  • Effects/Importance to Knowledge of Fallacies 1.) Correct forms of interference are often best illustrated and explained by contrasting them with incorrect forms. You cannot know the correct forms of thought without simultaneously knowing the incorrect form. You cannot think correctly unless you avoid thinking incorrectly; and you can neither avoid incorrect thinking nor detect incorrect thinking unless you are skilled in recognizing incorrect thinking. 2.) The study of fallacies will serve as a review of much of what we have already seen. You should not consider fallacies in isolation from the other parts of logic, but intimately connected with them. 3.) Readiness in recognizing fallacies will help you apply the principles of logic to everything you read or hear and put you on your guard against the more common sources of deception. 4.) Finally, the ability to call a fallacy by name will give you a great advantage over an opponent in discussion and debate.
  • 1. Fallacies of Language Aristotle lists six fallacies of language. The first five are various kinds of ambiguity and consist of using an expression in different senses in different parts of an argument but proceeding as though it were used in the same sense. A. Equivocation consists in using a word that has the same spelling or sound, but a different meaning, in different parts of an argument. The word need not be an equivocal term in the strict sense the ambiguous use of an analogous term or a change in the way a term is used (that is, an illegitimate shift of supposition) can suffice.
  • Example (the equivocal use of the word “natural” What is natural is good; but to make mistakes is natural; therefore to make mistakes is goodIn its first occurrence, the word “natural” means “constituting or perfecting anature”; in its second occurrence, it means “due to the limitations of nature”.Only in the first sense of the word is it true that what is natural is good. (thissyllogism also incurs the fallacy of four terms).
  • Example: the equivocal use of ‘violate of law” and of “man” He who violates the law should be punished; but when we illustrate fallacies we violate many laws; therefore when we illustrate fallacies we should be punished.He who violates a moral law perhaps should be punished but hardlyone who violates a law of logic. “Man” can be predicted of many; but you are a man; therefore you can predicted by many.The concept “man” can be predicted of many; however, you are notthe concept “man” but a real man.
  • B. Amphiboly is syntactical ambiguity. It consists in using a phrase whose individual words are univocal but whose meaning is ambiguous because the grammatical construction can be interpreted in various ways. When king Pyrrhus asked the oracle whether he would conquer the Romans, the oracle answered in the following Latin hexameter: Aio te, Aeacide, Romanosvincer posse. (Pyrrhus the Romans can, I say, subdue.) Who was to conquer whom? King Pyrrus made the disastrous mistake of thinking that he was to conquer the Romans rather than the Romans were to conquer him.
  • Similar to this is the response that the oracle gave to KingCroesus when he was planning a war against the Persians. If Croesus wages war against the Persians, he will destroy a mighty kingdomWhose kingdom? His own? Or the Persians? The oracle did notsay, but the event proved that it was to be his own.
  • c. Composition consists in taking words or phrases as a unit when they should be taken separately. Cajus falls into this fallacy when he admits that thieves and murderers are excluded from the kingdom of heaven, but then denies that he himself is excluded since he is only a thief but not a murderer.
  • d. Division is the converse of the fallacy of composition and consists in taking separately what should be taken together as a unit. You fall into this fallacy when you argue; All in this room weigh about two tons; but Mary Alice in in this room; therefore Mary Alice weighs about two tons. “ All in this room” is to be understood collectively in the major premise; but in the conclusion you proceed as though it had been taken distributively; you divide, or separate, what is true only when taken together as a unit.
  • e. Accent consists in the ambiguous use of a word that has different meanings when it is accented differently. This fallacy is the same as equivocation except that, strictly speaking, words having different accents are not the same words. Example: “John is not a depraved murderer” - emphasizing “depraved”, you deny that john is depraved without stating whether or not ha is a murderer; if you emphasized “murderer”, you deny that he is a murderer without, however, stating whether or not he is depraved. “Thou shall not bear false witness against thy neighbor” If you emphasized “shall not bear”, you suggest the one should not tolerate false witness; if you emphasized “false” you hint that it is all right to say evil things about your neighbor.
  • f. Figures of Speech is a special type of false analogy that consists in wrongly inferring similarity of meaning from similarity of word structure.Example: Note the words “immaterial”, “insoluble” and “inflammable” What is immaterial is not material and what is insoluble is not soluble; therefore what is inflammable is not flammable.In “immaterial” and “insoluble” the prefix “im-” or “in” is a negativeparticle; but in “inflammable” it is an intensive particle.
  • Famous example of fallacy in Mill’s Utilitarianism: The only proof capable of being given that an object is visible is that people actually see it. The only proof that a sound is audible is because people hear it,; and so of the other sources of our experience. In like manner, I apprehend, the sole evidence it is possible to produce that anything is desirable, is that people do actually desire it.This fallacy rests on the false assumption that, in the word “desirable”,that suffix “ible” (or “-able”) must mean “capable being…” since ithas this meaning in “visible and Audible”
  • 2. Fallacies not of Language Aristotle lists seven fallacies not of language. They have this in common, that all of them arise from some kind of confusion about the things that are spoken of. Either what is essential to a thing is confused with what is merely accidental. a. Accident consists in affirming or denying of a thing what has been affirmed or denied only of some accidental modification or condition of the thing, or vice versa. The sophist’s dialogue with the acquaintance of Coriscus illustrates this fallacy. “Do you know Coriscus?” “Yes” “Do you Know the man who is approaching with his face muffled?” “No.” “But he is Coriscus; you have both affirmed and denied that you know Coriscus.”
  • To have his face muffled is an accident in Coriscus; it is possible to knowCoriscus without knowing him according to this particular accidentalcondition. ( you can know him without always recognizing him.) youillustrate the same fallacy when you argue: “ You say that you ate what you brought; but you brought raw meat; therefore you must have eaten raw meat.”You did not intended to assert a complete identity between what you ate andwhat you brought. All you wanted to say is that they were substantially thesame; you did not intend to deny that the accidental condition of the meatwas change by cooking.
  • A conditional form of this fallacy consist in arguing that a thing itself should beforbidden or destroyed because its use sometimes leads to abuse. The abuseshould be eliminated, of course; but it does not fallow from this that the useshould also be eliminated. Alcoholic drinks lead to drunkenness and should therefore be forbidden.You can construct a parallel argument which is obviously absurd. Good food leads to overeating and should therefore be forbiddenYou might have a valid argument, through, if you show that the use of a thing isinseparable from its abuse and that the abuse always has serious evilconsequences.
  • b. Confusion of Absolute and Qualified Statement Under this heading we shall treat of two distinct but closely related fallacies. The first of these consist in using a principle that is restricted in its applicability as thought it were an absolutely universal principle, and thus applying it to cases for which it was not intended. What is true only with qualification or limitation is taken to be true absolutely or without any qualification or limitation. We illustrate this fallacy when we argue: Water boils at 212 Fahrenheit; therefore water boils at 212 Fahrenheit on the top of mount Everest. The premise is not true absolutely but only with the limitations “under an atmospheric pressure corresponding to 760 mm.of mercury.” hence, when we use this premise to infer that water boils at 212 Fahrenheit on the top of mount Everest, we are applying a principle to a case that nit was not intended to cover. We do the same when we argues
  • Germans are good musicians; therefore this Germans is a good musician.The premise is true of Germans as a group or in general, but not of eachindividual Germans ( this example, if expressed in a complete syllogism,would incur the fallacy of undistributed middle since the middle term“German” would be particular in each occurrence.)_The other form of this fallacy consist in assuming that an absolute statementis implied in a qualified, or limited, statement when it is actually not impliedtherein. Compare the following propositions: 1. John is as good doctor; therefore John is a doctor . 2. He gave me $1000 of counterfeit money; therefore he gave me $ 1000.“John is a good doctor” implied the absolute statement that John is a doctor;but “ He gave me $1000 of counterfeit money” does not implied theabsolute statement that he gave me $1000.
  • c. Ignoratio Elenchi The fallacy of ignoratio elenchi consist in providing a conclusion other than the one that should be proved. It is called by various names; for instance, “ the fallacy of irrelevant conclusion.” “ ignorance of the question.” “ Ignoring the issue,” “ missing the point,” and so on. The fallacy gets it’s a name from the Latinized form of the Greek word elenchos, which means “refutation.” in order to refute a statement, you must establish its contradictory of the statement to be refuted, you are said to be “ignorant of the refutation.” Suppose, for instance, that someone uses the following argument to refute the Catholic claim that the pope is infallible.
  • There have been bad popes; therefore the pope is not infallible.Suppose, too, that this opponent of papal infallibility has proven thatthere were a few bad popes. The question is, is the fact that there havebeen a few bad popes really inconsistent with the popes infallibility?The fact proves that the popes is not impeccable; as in many others, anignoratio elenchi could have been avoided by clarifying the exactpoint at issue through precise definition.The following argument of the young lad who denied the guilt of his adultfriend who had been sent to prison for murdering his wife also incurs anignoratio elenchi; He wasn’t guilty. He was nice to all the kids and very athletic. We played basketball and water skied with him and had wonderful times. He’d do anything for anybody.
  • Ignoration elinchi is very common and assumes many minor forms.The following are the most common: 1.) Argumentum ad Hominem – ignores the issue and attacks the person of an opponent instead. It includes such things as personal abuse, attack on man’s character or nationality or religion, “mud slinging,” “name calling,” charges of inconsistency, retorting an argument and so on. 2.) Argumentum ad Populum (appeal to the people) – is an appeal to popular prejudices rather than to reason. Every election year supplies altogether too many examples of this fallacy. 3.) Argumentum ad Misericordiam (appeal to pity) – ignores the point at issue and appeals, instead, to our instinct to have conpassion on the unfortunate.
  • 4.) Argumentum ad Verecundiam – is an appeal to misplacedauthority. It aims at overawing people by appealing to themisplaced authority or to the dignity of those who hold an opinionrather than to their special competence in matter under discussion.5.) Argumentum ad Baculum (appeal to the stick) – is an appeal tophysical force or moral pressure.
  • d. Begging the Question The fallacy of begging the question, or petitio principii, consist in assuming under some form or other the conclusion that should be proved and using it as a premise to prove the very same conclusion. This fallacy occur in two forms. The first form consist in using the same or an equivalent proposition as both premise and conclusion,as in the following examples, Whiskey causes drunkenness because it is intoxicating the soul is immortal because it cannot die morphine induces sleep because it has soporific effects. Both the premise (the “because” clauses) and the conclusions state exactly the same thing and differ from one another only verbally.
  • The second form consist in using a premise that cannot beknown to be true unless the conclusion is first known to be true,as in the following example: All in this room are wearing shoes; but Martha is in this room; therefore Martha is wearing shoes.The major premise is an enumerative universal and cannot beknown to be true unless the conclusion is first to be true. Youcannot know that all in this room are wearing shoes unless youfirst know that Martha is wearing them.
  • e. False Cause We must distinguish between the Aristotelian fallacy of false cause ( non causa pro causa) and the much more important fallacy to which later logicians give the same name. The Aristotelian fallacy of false cause consist in drawing an absurd conclusion from an assumption that is falsely imputed to an opponent or wrongly assumed to underlie a thesis. What is not the cause or reason for a thesis is assumed to be cause or reason. Suppose, for example, that a sophist’s opponent has made statement that the death penalty for murder is just, and the sophist argues as follows: The claim that the death penalty for murder is just leads to an absurdity. If the death penalty for murder is just and if , moreover, punishment is just precisely insofar as it is an effective deterrent from crime, it would follow that it would be equally just to inflict the death penalty for pocket- picking
  • f. Consequent The fallacy of the consequent consist in inferring that an antecedent is true because its consequent is true, or that a consequent is false because its antecedent is false. This fallacy is based on the mistaken opinion that the relationship of an antecedent and its consequent in regard to truth and falsity is always reciprocal. The fallacy of the consequent can also be incurred in categorical syllogisms. Any notion included in the comprehension of a concept. Whether as a constitutive note ( genus and difference) or as a derived note (logical property) - is a consequent of that concept, and in relation to its consequent the concept itself is an antecedent. In this sense the notion “animal” “ organic” “ material, and so on, are consequents of the antecedent “dog”.
  • In the minor premise of the following syllogism the term “animal”, which isa consequent of “dog”. Is a predicated of the minor term “Moby Dick” andin the conclusion its antecedent (“dog”) is the predicated of the same term: A dog is an animal but Moby Dick is not a animal therefore Moby Dfick is not an animalThis example not only incurs the fallacy of positing the consequent but alsothe formal fallacy of an undistributed middle term.In the minor premise of the following syllogism the term “dog” which is anantecedent of “animal” is denied of the minor term “Moby Dick” and in theconclusion its consequent is denied of the same term. A dog is an animal; but Moby Dick is not a dog; therefore Moby Dick is not an animal.
  • g. Many Question The fallacy of many question consists in asking either a multiple question as though it were a single question- or a question involving a supposition as though it involving no supposition - and then demanding a simple yes or no for an answer and thus tricking someone into making admissions he did not intent to make. Consider the following multiple question which is proposed as though it were a single question. Is he a democrat with socialistic tendency? If he is both a democrat and a man of socialistic tendencies, the answer may be a simple yes but if not a democrat and a socialistic the answer may be a simple no.
  • h. Other Fallacies The following fallacies are not included in Aristotle’s list of fallacies, but are important enough to merit a brief notice. is the Latin for “it does not follow.” in a sense every 1) Non Sequitur invalid argument is a sequitur, just as every invalid argument is also an ignoratio elechi; but the name “non sequitur” is generally restricted to a series of true but unrelated propositions that simulate the structure of a syllogism; for instance; Cows give milk; but sheep have wool; therefore goats chew cud.
  • 2) The Argumentum Ad Ignorantiam , or Appeal to Ignorance infers that a statement is false because it cannot be proved , or true because it cannot be refuted. The assumption that a man is guilty until he proves himself not guilty is an example of this fallacy.3) The fallacy of Suppressing the Fact consists in selection only the fact that favor an opinion and suppressing, or ignoring, all fact that are against it. By a careful selection of quotations you can often give the impression that a writer holds an opinion that is just the opposite of what he really holds4) The Argument from silence infers that an alleged fact did not take place because it is not recorded in writings in which it would surely have been recorded if it had taken place. This argument can be legitimate, but is often misused. To know for certain that, if an event had taken place, it would have been recorded is often difficult and frequently impossible
  • 5) The Fallacy of False Assumption consists in using a false principle or false statement of fact as an unexpressed premise (or at least as a presupposition) of an argument. It is not a fallacy at all in the Aristotelian sense but an error. The fallacy of false assumption is incurred most frequently in enthymemes whose unexpressed member is false, as in the following example.6) Fallacies of Illicit Generalization consists in masking a generalization on insufficient evident. Those fallacies are incident to induction.7) The Fallacy of False Analogy will be treated in connection with induction. Actually it is an ignoratio elenchi.