Formal/Logical Fallacies Informal/Material Fallacies

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. 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. Classifications of
Formal / Logical
Fallacies

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. 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. c. Fallacy of Redundant Definition
someunnecessary termsareadded
to thedefinition. The term used is
repeated and not essential.
Example:
Jayson is a handsome man.

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. e. Fallacy of CircularDefinition
thedefinition should not be
synonymousto theterm it defines.
Example:
• A man is a male person.
• Circle is round.

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. 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. 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. 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. 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. 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. 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. 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. 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. Example:
All Bacolodnons are Negrosanons.
(convertend)
All Negrosanons are Bacolodnons.
(converse)

19. b. Fallacy of Incorrect Obversion
thisariseswhen, in changing the
obvertend (original proposition)
from theaffirmative, themeaning
of theoriginal proposition is
changed.

20. Examples:
All BCCnians are Hinigaranos.(obvertend)
Some BCCnians are non-Hinigaranons.
(obverse)

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. Example:
•All Cebuanos are Filipinos.
•All Negrosanons are Ilonggos.
•Therefore, all Negrosanons are
Filipinos.

23. b. Fallacy of Negative Premises
thisisknown asthefallacy of two
negativeswhich occurswhen we
draw aconclusion from two
negativepremises.

24. Example:
•No Cebuanos are Ilonggos.
•No Cebuanos are Ilocanos.
•Therefore, no Ilocanos are
Ilonggos.

25. c. Fallacy of Undistributed
Middle
thisfallacy violatesthesyllogistics
rulewhich prescribesthat the
middleterm must beused at least
onceasuniversal in any of the
premises.

26. Example:
•Some politicians are businessmen.
•Some teachers are politicians.
•Therefore, some teachers are
businessmen.

27. d. Fallacy of ParticularPremises
known asthefallacy of two
particulars. When wedraw a
conclusion from two particular
premises, thisfallacy is
committed.

28. Example:
•Some Filipinos are Cebuanos.
•Some Half-Chinese are Cebuanos.
•Therefore, some Half-Chinese are
Filipinos.

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. Example:
•All Filipinos are hospitable.
•Some Chinese are not Filipinos.
•Therefore, all Chinese are not
hospitable.

31. f. Fallacy of Illicit Major
it developswhen themajorterm
becomes universal (distributed)
in the conclusionwhereas it is
only particular(undistributed) in
the majorpremises.

32. Example:
•Some Asians are Filipinos.
•Arabians are not Asians.
•Therefore, all Filipinos are not
Arabians.

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. (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. Example:
First Figure:
I --- some Mis Pp
E--- No S is M
O --- some S is not Pu

36. Example:
•Some parents are
hardworking.
•No children are parents.
•Some children are not
hardworking.

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.

38. TYPES OF
INFORMAL OR
MATERIAL
FALLACIES

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. a. Fallacy of Equivocation
thisfallacy iscommitted when
sometermsareused in apremise
but with different meanings. There
arethreekindsof fallacy of
equivocation.

41. Three Kinds of
Fallacy of
Equivocation

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. 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. 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. b. Fallacy of Amphiboly
It arisesfrom theambiguoususe
not of asingleword but of aphrase
or of acompletesentence.
Fallacies in Language

46. Example:
•This child hermotherkilled.
•Forsale: Hyundai Carby a carboy
with damaged button.

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. 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. 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. 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. 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. 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. 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. j. Fallacy of Increment Premises
thispolicy occurswhen a
conclusion isdrawn from premises
that areirrelevant.

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.  Thisfallacy ariseswhen the
conclusion isreached by
unwanted premises. It also
ariseswhen theissueat hand is
ignored.
2. Fallacies of
Presumption

57. TYPES OF
FALLACIES OF
PRESUMPTION

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. Example:
Souls can neverdie because
they are immortal.

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. b. Fallacy of Evading the
Question
this fallacy is made to evade
the issue by using
techniques orModus
Operandi.

62. Types of Fallacy
of Evading the
Questions

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.  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.  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. Example:
•Mr. John Mark cannot be put
to prison because he is sick.

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. Example:
•Karl who was caught byKarl who was caught by
Clarence of cheating uses hisClarence of cheating uses his
money to settle arguments.money to settle arguments.

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.  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. Example:
My motherthreatens me that if I
will have a failing grade in this
semester, she will not support
my studies anymore.

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. Example:
Mr. Chavez offers Novy forher
college assistance but in return,
she will be his mistress.