Free and Critical Thinkers Meeting: Friday 23rd June 2000 Logic and Fallacies. How to spot a problem argument. There are a number of pitfalls to avoid when constructing a deductive argument; they are known as fallacies. A fallacy is a technical flaw which makes an argument unsound or invalid. Note that fallacious arguments often appear valid and convincing and only with close inspection does the logical flaw become apparent. Take note of those fallacies used ubiquitously in today’s society. We should be weary as many of us will fall into the trap of using these kinds of arguments to defend various propositions we put forward. List of Common Fallacies of Logic: Fallacies of Distraction False Dilemma/False Dichotomy: two choices are given when in fact there are three options From Ignorance: because something is not known to be true, it is assumed to be false Slippery Slope: a series of increasingly unacceptable consequences is drawn Complex Question: two unrelated points are conjoined as a single proposition Appeals to Motives in Place of Support Appeal to Force: the reader is persuaded to agree by force Appeal to Pity: the reader is persuaded to agree by sympathy Consequences: the reader is warned of unacceptable consequences Prejudicial Language: value or moral goodness is attached to believing the author Popularity: a proposition is argued to be true because it is widely held to be true Changing the Subject Attacking the Person: 1. the person's character is attacked 2. the person's circumstances are noted 3. the person does not practise what is preached Appeal to Authority: 1. the authority is not an expert in the field 2. experts in the field disagree 3. the authority was joking, drunk, or in some other way not being serious Anonymous Authority: the authority in question is not named Style Over Substance: the manner in which an argument (or arguer) is presented is felt to affect the truth of the conclusion Inductive Fallacies Hasty Generalization: the sample is too small to support an inductive generalization about a population Unrepresentative Sample: the sample is unrepresentative of the sample as a whole False Analogy: the two objects or events being compared are relevantly dissimilar Slothful Induction: the conclusion of a strong inductive argument is denied despite the evidence to the contrary Fallacy of Exclusion: evidence which would change the outcome of an inductive argument is excluded from consideration Fallacies Involving Statistical Syllogisms Accident: a generalization is applied when circumstances suggest that there should be an exception Converse Accident: an exception is applied in circumstances where a generalization should apply Causal Fallacies Post Hoc: because one thing follows another, it is held to cause the other Joint effect: one thing is held to cause another when in fact they are both the joint effects of an underlying cause Insignificant: one thing is held to cause another, and it does, but it is insignificant compared to other causes of the effect Wrong Direction: the direction between cause and effect is reversed Complex Cause: the cause identified is only a part of the entire cause of the effect Missing the Point Begging the Question: the truth of the conclusion is assumed by the premises Irrelevant Conclusion: an argument in defense of one conclusion instead proves a different conclusion Straw Man: the author attacks an argument different from (and weaker than) the opposition's best argument Fallacies of Ambiguity Equivocation: the same term is used with two different meanings Amphiboly: the structure of a sentence allows two different interpretations Accent: the emphasis on a word or phrase suggests a meaning contrary to what the sentence actually says Category Errors Composition: because the attributes of the parts of a whole have a certain property, it is argued that the whole has that property Division: because the whole has a certain property, it is argued that the parts have that property Non Sequitur Affirming the Consequent: any argument of the form: If A then B, B, therefore A Denying the Antecedent: any argument of the form: If A then B, Not A, thus Not B Inconsistency: asserting that contrary or contradictory statements are both true Syllogistic Errors Fallacy of Four Terms: a syllogism has four terms Undistributed Middle: two separate categories are said to be connected because they share a common property Illicit Major: the predicate of the conclusion talks about all of something, but the premises only mention some cases of the term in the predicate Illicit Minor: the subject of the conclusion talks about all of something, but the premises only mention some cases of the term in the subject Fallacy of Exclusive Premises: a syllogism has two negative premises Fallacy of Drawing an Affirmative Conclusion From a Negative Premise: as the name implies Existential Fallacy: a particular conclusion is drawn from universal premises Fallacies of Explanation Subverted Support (The phenomenon being explained doesn't exist) Non-support (Evidence for the phenomenon being explained is biased) Untestability (The theory which explains cannot be tested) Limited Scope (The theory which explains can only explain one thing) Limited Depth (The theory which explains does not appeal to underlying causes) Fallacies of Definition Too Broad (The definition includes items which should not be included) Too Narrow (The definition does not include all the items which shouls be included) Failure to Elucidate (The definition is more difficult to understand than the word or concept being defined) Circular Definition (The definition includes the term being defined as a part of the definition) Conflicting Conditions (The definition is self-contradictory) Fallacies Overview The point of an argument is to give reasons in support of some conclusion. An argument commits a fallacy when the reasons offered do not, in fact, support the conclusion. Each fallacy is described in the following format: Name: this is the generally accepted name of the fallacy Definition: the fallacy is defined Examples: examples of the fallacy are given Proof: the steps needed to prove that the fallacy is committed Note: Please keep in mind that this is a work in progress, and therefore should not be thought of as complete in any way. 1. Fallacies of Distraction Each of these fallacies is characterized by the illegitimate use of a logical operator in order to distract the reader from the apparent falsity of a certain proposition. 1.1 False Dilemma/False Dichotomy Definition: A limited number of options (usually two) is given, while in reality there are more options. A false dilemma is an illegitimate use of the "or" operator. Examples: (i) Either you're for me or against me. (ii) America: love it or leave it. (iii) Either support Meech Lake or Quebec will separate. Proof: Identify the options given and show (with an example) that there is an additional option. (Cedarblom and Paulsen: 136) 1.2 Argument From Ignorance (argumentum ad ignorantiam) Definition: Arguments of this form assume that since something has not been proven false, it is therefore true. Conversely, such an argument may assume that since something has not been proven true, it is therefore false. (This is a special case of a false dilemma, since it assumes that all propositions must ether be known to be true or known to be false.) As Davis writes, "Lack of proof is not proof." (p. 59) Examples: (i) Since you cannot prove that ghosts do not exist, they must exist. (ii) Since scientists cannot prove that global warming will occur, it probably won't. (iii) Fred said that he is smarter than Jill, but he didn't prove it, so it must be false. Proof: Identify the proposition in question. Argue that it may be true even though we don't know whether it is or isn't. (Copi and Cohen: 93, Davis: 59) 1.3 Slippery Slope Definition: In order to show that a proposition P is unacceptable, a sequence of increasingly unacceptable events is shown to follow from P. A slippery slope is an illegitimate use of the"if-then" operator. Examples: (i) If we pass laws against fully-automatic weapons, then it won't be long before we pass laws on all weapons, and then we will begin to restrict other rights, and finally we will end up living in a communist state. Thus, we should not ban fully-automatic weapons. (ii) You should never gamble. Once you start gambling you find it hard to stop. Soon you are spending all your money on gambling, and eventually you will turn to crime to support your earnings. If I make an exception for you then I have to make an exception for everyone. Proof: Identify the proposition P being refuted and identify the final event in the series of events. Then show that this final event need not occur as a consequence of P. (Cedarblom and Paulsen: 137) 1.4 Complex Question Definition: Two otherwise unrelated points are conjoined and treated as a single proposition. The reader is expected to accept or reject both together, when in reality one is acceptable while the other is not. A complex question is an illegitimate use of the "and" operator. Examples: (i) You should support home education and the God-given right of parents to raise their children according to their own beliefs. (ii) Do you support freedom and the right to bear arms? Have you stopped using illegal sales practices? (This asks two questions: did you use illegal practices, and did you stop?) Proof: Identify the two propositions illegitimately conjoined and show that believing one does not mean that you have to believe the other. (Cedarblom and Paulsen: 86, Copi and Cohen: 96) 2. Appeals to Motives in Place of Support The fallacies in this section have in common the practise of appealing to motions or other psychological factors. In this way, they do not provide reasons for belief. 2.1 Appeal to Force (argumentum ad baculum) Definition: The reader is told that unpleasant consequences will follow if they do not agree with the author. Examples: (i) You had better agree that the new company policy is the best bet if you expect to keep your job. (ii) NAFTA is wrong, and if you don't vote against NAFTA then we will vote you out of office. Proof: Identify the threat and the proposition and argue that the threat is unrelated to the truth or falsity of the proposition. (Cedarblom and Paulsen: 151, Copi and Cohen: 103) 2.2 Appeal to Pity (argumentum ad misercordiam) Definition: The reader is told to agree to the proposition because of the pitiful state of the author. Examples: (i) How can you say that's out? It was so close, and besides, I'm down ten games to two. (ii) We hope you'll accept our recommendations. We spent the last three months working extra time on it. Proof: Identify the proposition and the appeal to pity and argue that the pitiful state of the arguer has nothing to do with the truth of the proposition. (Cedarblom and Paulsen: 151, Copi and Cohen: 103, Davis: 82) 2.3 Appeal to Consequences( argumentum ad consequentiam ) Definition: The author points to the disagreeable consequences of holding a particular belief in order to show that this belief is false. Example: (i) You can't agree that evolution is true, because if it were, then we would be no better than monkeys and apes. (ii) You must believe in God, for otherwise life would have no meaning. (Perhaps, but it is equally possible that since life has no meaning that God does not exist.) Proof: Identify the consequences to and argue that what we want to be the case does not affect what is in fact the case. (Cedarblom and Paulsen: 100, Davis: 63) 2.4 Prejudicial Language Definition: Loaded or emotive terms are used to attach value or moral goodness to believing the proposition. Examples: (i) Right thinking Canadians will agree with me that we should have another free vote on capital punishment. (ii) A reasonable person would agree that our income statement is too low. (iii) Senator Turner claims that the new tax rate will reduce the deficit. (Here, the use of "claims" implies that what Turner says is false.) The proposal is likely to be resisted by the bureaucrats on Parliament Hill. (Compare this to: The proposal is likely to be rejected by officials on Parliament Hill.) Proof: Identify the prejudicial terms used (eg. "Right thinking Canadians" or "A reasonable person"). Show that disagreeing with the conclusion does not make a person "wrong thinking" or "unreasonable". (Cedarblom and Paulsen: 153, Davis: 62) 2.5 Appeal to popularity (argumentum ad populum) Definition: A proposition is held to be true because it is widely held to be true or is held to be true by some (usually upper crust) sector of the population. This fallacy is sometimes also called the "Appeal to Emotion" because emotional appeals often sway the population as a whole. Examples: (i) If you were beautiful, you could live like this, so buy Buty-EZ and become beautiful. (Here, the appeal is to the "beautiful people".) (ii) Polls suggest that the Liberals will form a majority government, so you may as well vote for them. (iii) Everyone knows that the Earth is flat, so why do you persist in your outlandish claims? (Copi and Cohen: 103, Davis: 62) 3. Changing the Subject The fallacies in this section change the subject by discussing the person making the argument instead of discussing reasons to believe or disbelieve the conclusion. While on some occasions it is useful to cite authorities, it is almost never appropriate to discuss the person instead of the argument. 3.1 Attacking the Person ( argumentum ad hominem ) Definition: The person presenting an argument is attacked instead of the argument itself. This takes many forms. For example, the person's character, nationality or religion may be attacked. Alternatively, it may be pointed out that a person stands to gain from a favourable outcome. Or, finally, a person may be attacked by association, or by the company he keeps. There are three major forms of Attacking the Person: (1) ad hominem (abusive): instead of attacking an assertion, the argument attacks the person who made the assertion. (2) ad hominem (circumstantial): instead of attacking an assertion the author points to the relationship between the person making the assertion and the person's circumstances. (3) ad hominem (tu quoque): this form of attack on the person notes that a person does not practice what he preaches. Examples: (i) You may argue that God doesn't exist, but you are just following a fad. (ad hominem abusive) (iii) We should discount what Premier Klein says about taxation because he won't be hurt by the increase. (adhominem circumstantial) (iv) We should disregard Share B.C.'s argument because they are being funded by the logging industry. (ad hominem circumstantial) (v) You say I shouldn't drink, but you haven't been sober for more than a year. (ad hominem tu quoque) Proof: Identify the attack and show that the character or circumstances of the person has nothing to do with the truth or falsity of the proposition being defended. (Barker: 166, Cedarblom and Paulsen: 155, Copi and Cohen: 97, Davis: 80) Appeal to Authority (argumentum ad verecundiam) Definition: While sometimes it may be appropriate to cite an authority to support a point, often it is not. In particular, an appeal to authority is inappropriate if: (i) the person is not qualified to have an expert opinion on the subject, (ii) experts in the field disagree on this issue. (iii) the authority was making a joke, drunk, or otherwise not being serious A variation of the fallacious appeal to authority is hearsay. An argument from hearsay is an argument which depends on second or third hand sources. Examples: (i) Noted psychologist Dr. Frasier Crane recommends that you buy the EZ-Rest Hot Tub. (ii) Economist John Kenneth Galbraith argues that a tight money policy is the best cure for a recession. (Although Galbraith is an expert, not all economists agree on this point.) (iii) We are neaded for nuclear war. Last week Ronald Reagan remarked that we begin bombing Russia in five minutes. (Of course, he said it as a joke during a microphone test.) (iv) My friend heard on the news the other day that Canada will declare war on Serbia. (This is a case of hearsay; in fact, the reporter said that Canada would not declare war.) (v) The Ottawa Citizen reported that sales were up 5.9 percent this year. (This is hearsay; we are not in a position to check the Citizen's sources.) Proof: Show that either (i) the person cited is not an authority in the field, or that (ii) there is general disagreement among the experts in the field on this point. (Cedarblom and Paulsen: 155, Copi and Cohen: 95, Davis: 69) 3.2 Anonymous Authorities Definition: The authority in question is not named. This is a type of appeal to authority because when an authority is not named it is impossible to confirm that the authority is an expert. However the fallacy is so common it deserves special mention. A variation on this fallacy is the appeal to rumour. Because the source of a rumour is typically not known, it is not possible to determine whether to believe the rumour. Very often false and harmful rumours are deliberately started in order to discredit an opponent. Examples: (i) A government official said today that the new gun law will be proposed tomorrow. (ii) Experts agree that the best way to prevent nuclear war is to prepare for it. (iii) It is held that there are more than two million needless operations conducted every year. (iv) Rumour has it that the Prime Minster will declare another holiday in October. Proof: Argue that because we don't know the source of the information we have no way to evaluate the reliability of the information. (Davis: 73) 3.3 Style Over Substance Definition: The manner in which an argument (or arguer) is presented is taken to affect the likelihood that the conclusion is true. Examples: (i) Nixon lost the presidential debate because of the sweat on his forehead. (ii) Trudeau knows how to move a crowd. He must be right. (iii) Why don't you take the advice of that nicely dressed young man? Proof: While it is true that the manner in which an argument is presented will affect whether people believe that its conclusion is true, nonetheless, the truth of the conclusion does not depend on the manner in which the argument is presented. In order to show that this fallacy is being committed, show that the style in this case does not affect the truth or falsity of the conclusion. (Davis: 61)