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Formal/Logical Fallacies
Informal/Material Fallacies

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  1. 1. FALLACIES  the reasoning orarguments which are valid but are actually invalid.  arguments, which you know are correct but definitely are not correct.  arguments that seem to be true but are actually false.
  2. 2. Formal / Logical Fallacies when the errorcommitted is on the violation of the antecedent - consequent relationship orthe rules of syllogism. It is sometimes called LOGICALFALLACY.
  3. 3. Classifications of Formal / Logical Fallacies
  4. 4. a. Fallacy of Definition thedefinition iswider than theterm it connotes. In thiskind of fallacy you should not widen or exaggeratethedefinition of the term to really understand thereality of the truth. A violation arises when we decrease the connotation of the definitions and widen theirdenotations. Example: •Man is an animal. 1. FALLACIES OF DEFINITION
  5. 5. b. Too Narrow Definition it violatestheruleof definition becausethedefinition istoo narrow. Violation arises when we unduly increase the connotation of the definition, thus narrowing its denotation. Example: • Man is an irritable rational man.
  6. 6. c. Fallacy of Redundant Definition someunnecessary termsareadded to thedefinition. The term used is repeated and not essential. Example: Jayson is a handsome man.
  7. 7. d. Fallacy of Accidental Definition someaccidental attributeswhich arenot useful areadded to thedefinition. Even without theseaccidental attributes, the meaning could still bedistinguished. Example: • Man is a rational being who knows how to dance and sing.
  8. 8. e. Fallacy of CircularDefinition thedefinition should not be synonymousto theterm it defines. Example: • A man is a male person. • Circle is round.
  9. 9. f. Fallacy of Obscure Definition it must besimpleenough to easily understand. Do not add terms which are different. They should be clear and simple. Example: • A net is a reticulated fabric decussated at regularintervals with interstices and intersections.
  10. 10. g. Fallacy of Figurative Definition do not useexaggeration in defining theterm. Figurative or metaphorical language must not be used. Example: • Love is the silverlink, the silken tie, which heart to heart, and mind to mind, in body and soul can bind.
  11. 11. h. Fallacy of Negative Definition do not useadefinition which isnot the meaning of theterm but rather give thereal meaning of theterm. Example: • An insecure person is one who is not secure. • A notebook is not a book.
  12. 12. a. Fallacies of Cross Division also known asoverlapping which is aviolation of thegolden ruleof logical division that wehaveto use only onefoundation or basisin defining theterm. 2. Fallacies of Division
  13. 13. Example: •If we divide BCCnians into Christians, Muslim and Adventist, we are using a single foundation. On the otherhand, if we divide BCCnians into Christians, Muslims, women and married, we are using more than one bases of division, namely, religion, sex and civil status. The result is cross division.
  14. 14. b. Fallacy of Too Wide Division meansthat wedo not go beyond what isreally meant by theterm. Example: Animals into: amphibians, reptiles, mammals, frogs, cows and crocodiles.
  15. 15. c. Fallacy of Too Narrow Division narrow means“limited in sizeor scope”. Here, thedefinition of aterm is incompleteor insufficient. You should completethedefinition of aterm. A good definition must becomplete. Example: Human: rational and animal. .
  16. 16. d. Fallacy of Remote Division definition should depend upon the basisof division. Example: • If we divide BCCnians into animals and plants intead of into men and women, we commit this fallacy.
  17. 17. 3. Fallacies of Eduction a. Fallacy of Incorrect Conversion thisariseswhen aterm is undistributed (particular) in the convertend (original proposition) then distributed (universal) in the converse(inferred proposition).
  18. 18. Example: All Bacolodnons are Negrosanons. (convertend) All Negrosanons are Bacolodnons. (converse)
  19. 19. b. Fallacy of Incorrect Obversion thisariseswhen, in changing the obvertend (original proposition) from theaffirmative, themeaning of theoriginal proposition is changed.
  20. 20. Examples: All BCCnians are Hinigaranos.(obvertend) Some BCCnians are non-Hinigaranons. (obverse)
  21. 21. a. Fallacies of FourTerms (QuaternioTerminorem) thisfallacy occursif thereareactually fourterms in the syllogism and thereisno middle term that servesas themedium of comparison between theminor and themajor terms. 4. Fallacies in Categorical Syllogism
  22. 22. Example: •All Cebuanos are Filipinos. •All Negrosanons are Ilonggos. •Therefore, all Negrosanons are Filipinos.
  23. 23. b. Fallacy of Negative Premises thisisknown asthefallacy of two negativeswhich occurswhen we draw aconclusion from two negativepremises.
  24. 24. Example: •No Cebuanos are Ilonggos. •No Cebuanos are Ilocanos. •Therefore, no Ilocanos are Ilonggos.
  25. 25. c. Fallacy of Undistributed Middle thisfallacy violatesthesyllogistics rulewhich prescribesthat the middleterm must beused at least onceasuniversal in any of the premises.
  26. 26. Example: •Some politicians are businessmen. •Some teachers are politicians. •Therefore, some teachers are businessmen.
  27. 27. d. Fallacy of ParticularPremises known asthefallacy of two particulars. When wedraw a conclusion from two particular premises, thisfallacy is committed.
  28. 28. Example: •Some Filipinos are Cebuanos. •Some Half-Chinese are Cebuanos. •Therefore, some Half-Chinese are Filipinos.
  29. 29. e. Fallacy of Illicit Minor thisfallacy ariseswhen the minor term becomes universal (distributed) in the conclusion while it is only particular (undistributed) in theminor premises.
  30. 30. Example: •All Filipinos are hospitable. •Some Chinese are not Filipinos. •Therefore, all Chinese are not hospitable.
  31. 31. f. Fallacy of Illicit Major it developswhen themajorterm becomes universal (distributed) in the conclusionwhereas it is only particular(undistributed) in the majorpremises.
  32. 32. Example: •Some Asians are Filipinos. •Arabians are not Asians. •Therefore, all Filipinos are not Arabians.
  33. 33. 7. The IEO Fallacy it occurswhen wedraw a conclusion from IEO mood. The majorpremise isaparticular affirmative proposition, (I), and theminorpremises isauniversal negative proposition,
  34. 34. (E), theconclusion isaparticular negative proposition, (O), in compliancewith thesyllogistic rule that should onepremisebe particular, theconclusion also must be particular; should onepremise benegative, theconclusion must be also benegative.
  35. 35. Example: First Figure: I --- some Mis Pp E--- No S is M O --- some S is not Pu
  36. 36. Example: •Some parents are hardworking. •No children are parents. •Some children are not hardworking.
  37. 37. Informal/ Material Fallacies this arises from confusion or ambiguity due to the kind of term used.  they maybe classified as eitherfallacies in language or fallacies of presumption.
  39. 39. 1.Fallacies in Languagethistypeof fallacy iscommitted dueto lack of preciseness in the word, phrases, orsentences used to expressathought. The typesof fallacy which fall under thiscategory arethefollowing:
  40. 40. a. Fallacy of Equivocation thisfallacy iscommitted when sometermsareused in apremise but with different meanings. There arethreekindsof fallacy of equivocation.
  41. 41. Three Kinds of Fallacy of Equivocation
  42. 42. 1. Fallacy of Ambiguous Middle: The middleterm isused with two different meanings. Example: •A rulerhelps us to draw vertical line. •Joecris is a ruler. •Therefore, Joecris helps us to draw a vertical line.
  43. 43. 2. Fallacy of Ambiguous Major: When themajor term isused in two different senses. Example: •All chefs move only backward. •Sheila Del Rio, is a chef. •Therefore, Chef Sheila Del Rio moves only backward.
  44. 44. 3. Fallacy of Ambiguous Minor: when theminor term isused in two different senses. Example: •No animal is made of paper. •All pages are animals. •Therefore, no pages are made of paper.
  45. 45. b. Fallacy of Amphiboly It arisesfrom theambiguoususe not of asingleword but of aphrase or of acompletesentence. Fallacies in Language
  46. 46. Example: •This child hermotherkilled. •Forsale: Hyundai Carby a carboy with damaged button.
  47. 47. c. Fallacy of Accent Thisarisesfrom theuseof aword which changesmeaning when the accent on theword changes. Example: • Every falsity needscareand attention. • Every fallacy isfalsity. • Every fallacy needscareand attention.
  48. 48. d. Fallacy of Figure of Speech A wrong conclusion isdrawn dueto theuseof wordsthat aresimilar in structureor in meaning. Example: • Faithful is the opposite of unfaithful. • Fidelity is the opposite of unfaithful. • Therefore, Loyal is the opposite of
  49. 49. e. Fallacy of Composition Thisfallacy iscommitted aswordsor phrasesaretaken jointly or asaunit when they should betaken separately Example:  The students of BCC come from the different barrios in Binalbagan.  Georgia Anne is a student from BCC.  Georgia Anne is from the different barrios of Binalbagan.
  50. 50. f. Fallacy of Division Thisfallacy istheoppositeof composition. It takeswordsor phrases separately when it should betaken jointly or asaunit. Example: • BCCnian students speak english. • Jonamel is a BCCnian student. • Jonamel speaks english.
  51. 51. g. Fallacy of Accident Thisfallacy ariseswhen what is accident or superficial isemphasized over what isessential or basic. Example:  Jason wears elegant clothes.  Therefore, he looks handsome and wealthy.
  52. 52. h. Fallacy of False Cause It arrangeswrong causein acertain effect. Superstitionsarebased on this fallacy. Example:  Wounds cannot be healed because it’s Good Friday.
  53. 53. i. Fallacy of Hasty Generalization It consistsof arguing that what istrue to acertain classmust also betrueto all membersof thesameclass. Example:  Some mothers are overprotected to theirchildren.  All mothers are overprotected to theirchildren.
  54. 54. j. Fallacy of Increment Premises thispolicy occurswhen a conclusion isdrawn from premises that areirrelevant.
  55. 55. Example: •AJmust be a cum laude. •He is an active student. •He is a hardworking student. •He is an intelligent student. •He is BCC scholar. •Therefore, AJdeserves to be a cum laude.
  56. 56.  Thisfallacy ariseswhen the conclusion isreached by unwanted premises. It also ariseswhen theissueat hand is ignored. 2. Fallacies of Presumption
  58. 58. a. Fallacy of Begging the Question (Petitio Principii) – thisfallacy isthe assumption of thetruth of the preposition.  Not proven – assumestheconclusion under cover of synonymouswordsor expression.
  59. 59. Example: Souls can neverdie because they are immortal.
  60. 60.  Vicious Circle – usestwo unproved propositionsto proveeach other. Example: • The mind is spiritual because it is immaterial. • The mind is immaterial because it is spiritual.
  61. 61. b. Fallacy of Evading the Question this fallacy is made to evade the issue by using techniques orModus Operandi.
  62. 62. Types of Fallacy of Evading the Questions
  63. 63. • Thisignoresreal issues. It attacksthe character or personality of an opponent. Example: o Why should we believe in the statement of Mrs. Napolis o She is a liar. She was engaged in pork barrel scam. Argument to the man(Argumentum Ad hominem)
  64. 64.  It evadestheissueby appealing to passionsand prejudicesof the populace. Example: • Only a professional persons wear toxido. • Vitamins keep yourbody healthy. Argument to the people(Argumentum Ad Populum)
  65. 65.  It consistsof pleading for mercy and leaving reason aside.Weignorethe point of issueand appeal to our instinct to havecompassion towards theneedy, unfortunate, and the downtrodden. Argument to the Sympathy(Argumentum Ad Misericardian)
  66. 66. Example: •Mr. John Mark cannot be put to prison because he is sick.
  67. 67.  Wecommit thisfallacy when we appeal to thesenseof greed or cupidityof an individual. Instead of reasoning for an argument, webribe and usemoney to defeat the opponent. Argument to the Money(Argumentum Crumeman)
  68. 68. Example: •Karl who was caught byKarl who was caught by Clarence of cheating uses hisClarence of cheating uses his money to settle to settle arguments.
  69. 69.  Weignorethetruth or falsity of a proposition and assert thetruth becausepeopleareignorant about it. Example: • We cannot disprove that UFO exist, therefore, this existence is true. UFO exists. Argument to the Ignorance(Argumentum Ignoratium)
  70. 70.  Wecommit thisfallacy when we ignorethereal issueat hand and appeal to physical or moral pressurerather than to reason. Argument to the force(Argumentum Ad Baculum)
  71. 71. Example: My motherthreatens me that if I will have a failing grade in this semester, she will not support my studies anymore.
  72. 72.  Thisargument iscalled an appeal to gain or profit. Thisfallacy is committed when weignoretheissue and appeal to aperson to adopt a belief or policy in exchangefor the advantageoffered. Argument to one’s own advantage(Argumentum Pansarilum)
  73. 73. Example: Mr. Chavez offers Novy forher college assistance but in return, she will be his mistress.