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Home , Affirming a disjunct, Argument from fallacy, Base rate fallacy, Denying the antecedent, Existential fallacy, Illicit major

University of Ottawa Faculty of Law (Civil Law Section)

From the SelectedWorks of Hon. Gerald Lebovits

July, 2016

Say It Ain’t So: Leading Logical in Legal – Part 1 Gerald Lebovits

Available at: https://works.bepress.com/gerald_lebovits/297/ JULY/AUGUST 2016 VOL. 88 | NO. 6 JournalNEW YORK STATE BAR ASSOCIATION

Highlights from Today’s Game: Also in this Issue Exclusive Use and Domestic Trademark Coverage on the Offensive Violence Health Care Proxies By Christopher Psihoules and Jennette Wiser Litigation Strategy and Dispute Resolution What’s in a Name? That Which We Call Surrogate’s Court UBE-Shopping and Portability THE LEGAL WRITER BY GERALD LEBOVITS

Say It Ain’t So: Leading Logical Fallacies in Legal Argument – Part 1

o argue effectively, whether oral- fact.3 Then a final conclusion is drawn able doubt. The jury has reasonable ly or in writing, lawyers must applying the asserted fact to the gen- doubt. Therefore, the jury hesitated.”8 Tunderstand and how logic eral rule.4 For the to be valid, The : Just because the jury had can be manipulated through fallacious the premises must be true, and the a reasonable doubt, the jury must’ve reasoning. A logical fallacy is an inval- conclusion must follow logically. For hesitated. The jury could’ve been id way to reason. Understanding falla- example: “All men are mortal. Bob is a entirely convinced and reached a con- cies will “furnish us with a means by man. Therefore, Bob is mortal.” clusion without hesitation. which the logic of practical argumen- might not be valid, tation can be tested.”1 Testing your though, even if their premises and con- argument against the general types of clusions are true. For example: “All Great lawyers use fallacies exposes whether your logic is cats are mammals. Some mammals are sound logic to trump sound or unsound. Even more impor- excellent swimmers. Therefore, some tant, being aware of fallacies will tell cats are excellent swimmers.”5 It’s true the average argument. you when others are using fallacious that all cats are mammals. It’s also true arguments against you — and how that some mammals are excellent swim- 2. you can best respond. This article will mers. But “the fact that cats are mam- This fallacy exists in if/then statements help lawyers identify potential falla- mals and that some mammals are excel- when a writer who denies an anteced- cies in arguments. lent swimmers doesn’t prove anything ent suggests that the reader should Good lawyers must craft persua- about the swimming ability of cats.”6 also reject the consequent. sive arguments that make sense. Great Two general groups of fallacies Example: If the subject of a contract lawyers use sound logic to trump exist: Formal fallacies, which are falla- is the transfer of an interest in land, the average argument. Great law- cious because they’re based on formal then the contract should be in writ- yers are well-versed in formal logic logic, and informal fallacies, which are ing. The subject of this contract is and the different ways of reasoning. fallacious because of their content. In not a transfer of an interest in land. That’s why great lawyers use induc- this two-part column, the Legal Writer Therefore, the contract shouldn’t be in tive and in their begins with formal fallacies. In the next writing.9 arguments. Deductive reasoning is a issue of the Journal, we continue with The fallacy: A contract that doesn’t form of argumentation that presumes informal fallacies. transfer an interest in land doesn’t that if the premises of the argument need to be in writing. But other kinds are true, the conclusion must also be Formal Fallacies of contracts should also be in writ- true. is a form of In written or oral argument, “formal ing. Simply denying the antecedent is argumentation in which the premises fallacies are arguments that are defec- insufficient to deny the consequent. strongly support the conclusion. tive because of their form, without A syllogism is a common form of regard to content.”7 The following is a 3. argumentation that applies deductive list of formal fallacies and what makes This fallacy occurs when one premise reasoning. Familiarity with the form them fallacious. is true, but the writer suggests that the of leads to strong argu- other must be false: A or B. A is true. ments. A legal syllogism should have 1. Therefore, B is false. three clauses. Syllogisms start with This logical fallacy occurs when the Example: Morgan is a judge or an a single general premise, called the consequent is said to be true and thus attorney. Morgan is a judge. Therefore, major premise, stating the rule being that the antecedent must also be true. Morgan isn’t an attorney. applied.2 Then a second premise, Example: “If the evidence makes the called the minor premise, asserts a jury hesitate, then the jury has reason- Continued on Page 58

64 | July/August 2016 | NYSBA Journal The Legal Writer 7. The Base Rate 10. The “Hot Hand” Fallacy Continued from Page 64 The base-rate fallacy occurs when a This fallacy assumes that past suc- The fallacy: Morgan is a judge so writer “ignor[es] statistical informa- cesses or failures will dictate the same she can’t be an attorney. It’s possible tion” in making an argument. Instead outcome for future events. that Morgan is a part-time judge and a of relying on statistics, the writer uses Example: Ms. Thompson has won practicing attorney. A false assumption irrelevant information to suggest a his past five cases. Therefore, she has is drawn that if one clause is true, the conclusion.11 a “hot hand” and will inevitably win other must be false. Example: Judge Smith grants five the next case. percent of the motions before him. The fallacy: Because Thompson has 4. Denying a Conjunct Mr. Jones is our firm’s top attorney. been successful in her past five cases, A writer denies the conjunct when Therefore, Judge Smith will grant she’ll win her next case. This fallacy either the antecedent or the consequent Jones’s motion. is subtly different from the gambler’s is false but contends that the other The fallacy: Based on the statistics, fallacy. The past success or failure will must be true.10 Judge Smith grants only five percent of continue in the “hot hand” fallacy. In Example: The defendant is not both his motions. That Jones is a top attor- the gambler’s fallacy, you predict that guilty and innocent. The defendant is ney doesn’t ensure that Jones’s motion your luck will be different on the next not guilty. Therefore, the defendant is will be granted. outcome. innocent.

Familiarity with the form of syllogisms leads to strong arguments.

The fallacy: It’s logically wrong to 8. The Conjunctive Fallacy 11. Multiple Comparisons assume that because the defendant The conjunctive fallacy “indicates that This fallacy arises when statistical evi- is not guilty, the defendant must be the conjunction of two events is more dence is presented to support your innocent. The defendant might be likely than one event.”12 argument. Statistical evidence “cannot innocent, but the truth of both prem- Example: Ms. Anderson is a brilliant guarantee . . . the truth . . . [I]t can only ises doesn’t imply the defendant is law student who’s ranked number one provide that the answer is within a cer- innocent. Defendants found not guilty at her law school. Ms. Anderson will tain margin of error.”15 The more com- aren’t necessarily innocent. be likely both a law professor and an parisons one draws between condi- attorney when she graduates. tions, “the more likely it is that an erro- 5. Commutation of Conditionals The fallacy: Because Ms. Anderson is neous result will occur by chance.”16 A commutation of conditions switches an excellent law student, it’s likely she’ll Example: One hundred studies com- the antecedent and the consequent. be both a professor and an attorney. pared the crime rate between males Example: If the judge isn’t in the court- Concluding that Ms. Anderson will be and females. Eighty showed no signifi- room, then there’s no trial. Therefore, both a law professor and an attorney cant difference. Ten showed that males if there’s no trial, the judge isn’t in the is unwarranted from the premise that are twice as likely to commit crimes courtroom. she’s a brilliant law student. than females. Ten showed that males The fallacy: The judge is in the court- are half as likely to commit crimes than room only if there’s a trial. It’s pos- 9. The Gambler’s Fallacy females. Thus, males are more likely to sible that the judge is in the courtroom The gambler’s fallacy makes the commit crimes than females. when no trial is taking place. unwarranted assumption that “the The fallacy: The result that says odds for an event with a fixed prob- males are half as likely to commit 6. Improper ability increase or decrease depending crimes is ignored. From the 100 cited Improper transposition negates both on recent occurrences.”13 The gam- studies, one can’t conclude that males the antecedent and the consequent: bler’s fallacy specifically “deals with are more likely to commit crimes than If A, then B. Therefore, if not-A, then individuals’ predictions concerning a females. not-B. single event.”14 Example: If there’s an arsonist, Example: Mr. Brown lost five con- 12. there’s a fire. If there’s no arsonist, secutive cases this year. He’s bound to The illicit major is a “form of categori- there’s no fire.” win his sixth case. cal syllogism in which the major term The fallacy: Arsonists are the only The fallacy: Because Mr. Brown lost is distributed in the conclusion, but not cause of fires. Negating both the ante- his past five cases, he’ll win his next in the major premise”17: If all X are Y cedent and the consequent leads to an case. The outcome of the past five cases and all Z are not X, then all Z are not Y. improper transposition and is logically has no effect on whether he’ll win his Example: All prosecutors are law- unsound. next case. yers. No public defenders are prosecu-

58 | July/August 2016 | NYSBA Journal tors. Therefore, no public defenders are The fallacy: Muhammad Ali wore, 19. lawyers.18 and judges wear, robes, so Muhammad The existential fallacy occurs when The fallacy: Public defenders can’t Ali was a judge. The fallacy in this a writer makes a “some” conclusion be lawyers, because public defenders example is that the middle term, based on two “all” terms. aren’t prosecutors. Not all lawyers are “robes,” is undistributed in the conclu- Example: All robbers are criminals. prosecutors. A public defender could sion. Judges and great boxers are two All criminals should be sentenced to be a lawyer. The fallacy of the illicit examples of people who wear robes. jail. Therefore, some robbers should be major makes the writer’s argument But this isn’t enough to draw a logical sentenced to jail. flawed because the term “lawyers” connection.23 The fallacy: Some robbers should be is undistributed in the major (first) sentenced to jail because all robbers premises, but distributed in the conclu- 16. Drawing an Affirmative should be jailed. There must be an sion.19 Conclusion from a Negative “all” conclusion, because both prem- Premise ises have “all” terms. 13. This fallacy occurs in syllogisms that The illicit minor occurs when “the draw a positive conclusion from a 20. Illicit Contraposition minor term is distributed in the con- negative premise. An illicit contraposition occurs when clusion, but not in the minor prem- Example: Criminals are not good. Ms. a writer switches and then negates the ise”20: If all X are Y and all Y are Z, Williams is not a criminal. Therefore, subject and predicate terms. then all Z are X. Ms. Williams is good. Example: Some attorneys are judges. Example: All lawyers are intelligent, The fallacy: Because Ms. Williams Some non-judges are non-attorneys. and all intelligent people are profes- isn’t a criminal, she must be a good The fallacy: The conclusion that sional. Therefore, all professional peo- person. The conclusion in this example some non-judges are non-attorneys ple are lawyers. can’t be affirmative: “If either premise might be correct, but that conclusion The fallacy: The term “professional” is negative the conclusion must be can’t be inferred from the first prem- is undistributed. “Professional” is in negative.”24 ise. the minor premise (second premise) and in the conclusion. The conclusion 17. Drawing a Negative 21. Illicit Conversion that all professional people are lawyers Conclusion from Affirmative An illicit conversion happens when is fallacious. The conclusion doesn’t Premises a writer switches the subject and the follow the premises. This fallacy occurs in syllogisms that predicate in the conclusion. draw a negative conclusion from posi- Example: All lawyers are intelligent. 14. Exclusive Premises tive premises. Therefore, all intelligent people are The exclusive-premises fallacy is a syl- Example: All judges are lawyers. All lawyers.26 logism that has two negative premises. lawyers are intelligent. Therefore, no The fallacy: Most or all X are Y Example: No plaintiffs are defen- judge is intelligent. doesn’t mean that most or all Y are dants. No defendants are guilty. The fallacy: The conclusion draws X. It’s impossible to conclude that all Therefore, some plaintiffs are guilty. a negative conclusion from a posi- intelligent people are lawyers. The fallacy: This conclusion seems tive premise. Positive premises require logical, but no premises support this positive conclusions. 22. Unwarranted Contrast conclusion. The above example has Unwarranted contrasts occur when two negative premises. A relationship 18. Four-Term Fallacy the writer assumes that implicature between the premises can’t be formed A syllogism is invalid if it has four and implication are the same thing. just because the premises are both neg- terms rather than three. Syllogisms Implicature occurs when meaning is ative. The exclusive-premises fallacy must have three clauses. implied beyond what’s explicitly stat- dictates that “two negative premises Example: All attorneys went to law ed. Implication occurs when one states exclude the possibility of any relation school. All physicians went to medical a conclusion based on facts. The fallacy between them.”21 school. Therefore, all attorneys went to is this: If some X are Y, then some X medical school. are not Y. 15. Undistributed Middle The fallacy: The conclusion doesn’t Example: Some lawyers are judges, The fallacy of the undistributed middle logically follow from the premises. so some lawyers aren’t judges. term occurs when the middle term No relationship has been established The fallacy: The statement “some isn’t distributed in the other terms. between attorneys and physician. lawyers aren’t judges” is true, but that Example: “All judges wear robes. This fallacy can be fixed by adding can’t be inferred logically from the first The [late] Muhammad Ali w[ore] a second syllogism to establish the statement. “Some” doesn’t logically robes. Therefore, Muhammad Ali [wa]s relationship between attorneys and imply that it doesn’t mean “all.” The a judge.”22 physician.25 first clause is an affirmative statement.

NYSBA Journal | July/August 2016 | 59 It doesn’t logically imply that not all 26. Fallacy of Enthymeme The fallacy: Ms. Wilson might be the lawyers are judges. This fallacy occurs when the writer an excellent defense attorney, but the “omits either one of the premises or the premises don’t support the conclusion 23. Illicit Substitutions of conclusion. The omitted part must be that she should run for office. The con- Identicals (Masked-Man Fallacy) clearly understood.”28 clusion is a non-sequitur. The illicit substitutions of identicals Example: The defendant was found Part 2 of this column, which will occurs when the writer “confus[es] guilty. Therefore, he’s going to jail. appear in the next issue of the Journal, the knowing of a thing (extension) with The fallacy: An omitted premise sug- will cover informal fallacies in legal the knowing of it under all its various gests that the defendant was on trial. argument. n names or descriptions (intension).”27 The reader can imply that a defendant Example: A witness believes that the found guilty must have been tried. But Gerald Lebovits ([email protected]), an criminal wore a mask. The witness omitting the premise is fallacious. acting Supreme Court justice in Manhattan, then testifies that she didn’t believe is an adjunct professor of law at Columbia, that the defendant committed the 27. Anecdotal Fallacy Fordham, NYU, and New York Law School. For crime. Therefore, the defendant is not The anecdotal fallacy occurs when the their research, he thanks judicial interns Reid the masked criminal. writer tries to justify a conclusion based Packer (Hofstra) and Ziqing Ye (Fordham). The fallacy: This fallacy confuses the on a personal experience or event. witness’s beliefs with the overall con- Example: Ms. Smith argues that a 1. Andrew Jay McClurg, Logical Fallacies and clusion that the defendant is not the law should be passed to fund health- the Supreme Court: A Critical Examination of Justice masked criminal. ier lunch options in public schools. Rehnquist’s Decisions in Criminal Procedure Cases, 59 Mr. White challenges her argument by U. Colo. L. Rev. 741, 755 (1988). 24. saying that his child once contracted 2. Inspired by Clay McDonough, Critical Thinking and the Law: Logical Fallacies in Legal Writing, This fallacy assumes that a conclusion E. coli from lettuce. Therefore, White http://slideplayer.com/slide/8791572/ (last vis- from an argument containing a fallacy argues, healthier lunch options are a ited June 6, 2016). must be false. Not all arguments based bad idea. 3. Id. on a fallacy are fallacious. The fallacy: White’s conclusion is 4. Id. Example: The prosecution argues supported only by his own personal 5. Id. that all defendants are guilty. Robinson experience. It’s fallacious for him to 6. Id. is a defendant. Therefore, Robinson support his conclusion based on a per- 7. McClurg, supra note 1, at 764. is guilty, according to the prosecu- sonal anecdote. 8. Stephen M. Rice, Conspicuous Logic: Using tion. The defense, on the other hand, the Logical Fallacy of Affirming the Consequent as a argues that the prosecution is wrong. 28. Having Your Cake Fallacy Litigation Tool, 14 Barry L. Rev. 1, 17 (2010). According to the defense, the prosecu- This fallacy is committed when an 9. Inspired by Stephen M. Rice, Conventional Logic: Using The Logical Fallacy of Denying The tion committed the fallacy of affirming argument is vague and doesn’t have a Antecedent as a Litigation Tool, 79 Miss. L.J. 669, 680 the consequent. Therefore, the defen- clear position. (2010). dant is innocent. Example: Mr. Johnson is asked about 10. Bo Bennet, Logically Fallacious, https:// The fallacy: All the defense has done whether the new Clean Water Law is www.logicallyfallacious.com/tools/lp/Bo/ LogicalFallacies/76/Denying_a_Conjunct (last is expose a fallacy in the prosecution’s environmentally friendly. He answers visited June 6, 2016). argument. The defense is merely argu- that the new law will clean water 11. Inspired by Bo Bennet, Logically Fallacious, ing from fallacy — using fallacious but might reduce job opportunities https://www.logicallyfallacious.com/tools/lp/ reasoning to rebut the prosecution’s because some factories will be closed. Bo/LogicalFallacies/55/Base_Rate_Fallacy (last fallacious reasoning. The fallacy: The answer gives both visited June 6, 2016). sides of the new law instead of choos- 12. Paul H. Rubin, How Humans Make Political Decisions, 41 Jurimetrics J. 337, 340 (2001). 25. Fallacy of Inconsistency ing one of them. His position is unclear. 13. Ehud Guttel & Alon Harel, Matching This fallacy occurs when the speaker Probabilities: The Behavioral Law and Economics of argues that opposing statements are 29. Non-Sequitur Repeated Behavior, 72 U. Chi. L. Rev. 1197, 1201 n.7 both true. A non-sequitur appears when the con- (2005). Example: Yogi Berra used the fal- clusion doesn’t follow logically from 14. Id. lacy of inconsistency when he said, the premises. The conclusion of a non- 15. Adapted from J.R.H. Law, Cherry-Picking Memories: Why Neuroimaging-Based Lie Detection “Nobody goes there anymore. It’s too sequitur often isn’t supported by the Requires a New Framework for the Admissibility of crowded.” premises. Scientific Evidence Under FRE 702 and Daubert, 14 The fallacy: Yogi Berra’s statement is Example: Ms. Wilson is one of the Yale J. L. & Tech. 1, 23 (2011). humorous but inconsistent. If the place best defense attorneys in Albany. Her 16. Id. is crowded, people must be going record of getting clients acquitted is 17. Bo Bennet, Logically Fallacious, https:// there. But Yogi Berra said that no one excellent. Therefore, she should run for www.logicallyfallacious.com/tools/lp/Bo/ LogicalFallacies/109/Illicit_Major (last visited June goes there. Mayor of Albany. 6, 2016).

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