FALLACIES
COMMON AND RECURRENT ERRORS
IN REASONING
IMPORTANT STRATEGY TO IDENTIFY
THEM: TREAT PASSAGE AS AN
ARGUMENT WITH PREMISE AND
CONCLUSION AND DETERMINE WHAT
SORT OF STRUCTURE IT FOLLOWS.
SUBJECTIVIST FALLACIES:
INVOLVE THE REJECTION OF
OBJECTIVITY.




SUBJECTIVISM
STRUCTURES:
I BELIEVE/WANT P TO BE TRUE
P IS TRUE
SUBJECTIVISM CONT.

I DON’T WANT P TO BE TRUE



P IS NOT TRUE
I WAS BROUGHT UP TO BELIEVE P IS
TRUE


P IS TRUE
SUBJECTIVISM CONT.

P MAY BE TRUE TO YOU BUT NOT ME


P IS NOT TRUE
APPEAL TO MAJORITY


STRUCTURE:
THE MAJORITY BELIEVE P




P IS TRUE
WAVE OF THE FUTURE ARGUMENT
THE DISBELIEVE IN P WILL RESULT
IN FALLING BEHIND OTHERS


P SHOULD BE CONSIDERED TRUE
APPEAL TO EMOTION


STRUCTURE:
AN EMOTIONAL RESPONSE OCCURS
DUE TO P


P IS TRUE OR P IS FALSE
APPEAL TO FORCE

THERE WILL BE BAD
CONSEQUENCES FOR NOT
ACCEPTING P AS TRUE



P IS TRUE
PRACTICE QUIZ 6.1., P.133.
FALLACIES INVOLVING
CREDIBILITY

APPEAL TO AUTHORITY

Structure:
X SAYS P IS TRUE, X IS A SOCALLED AUTHORITY, STAR,
IMPRESSIVE PERSON


P
IS TRUE
JUSTIFIED APPEAL TO
AUTHORITY



CONDITIONS TO BE SATISIFIED
BEFORE AN APPEAL TO AUTHORITY
CAN BE JUSTIFIED.
1. The authority is competent; an expert in
the area and in a position to know what
happened
2. The authority must be reporting what
s/he knows objectively. S/he must be telling
the truth.
AD HOMINEM (AT THE MAN
OR PERSON)


Structure:
X SAY P + X HAS SOME NEGATIVE
TRAIT




P IS NOT TRUE
FORMS:
CRUDE FORM: NAME CALLING AND
INSULTS
OTHER FORMS AND SPECIES
OF AD HOMINEMS



TU QUOQUE “YOU’RE ANOTHER” OR
THE POT CALLING THE KETTLE
BLACK
POISONING THE WELL:
X HAS A VESTED INTEREST IN THE
TRUTH OF P



P IS UNTRUE
P.QUIZ 6.2. P.140
FALLACIES OF CONTEXT





SOME RELEVANCE OF PREMISE TO THE
CONCLUSION BUT EVIDENCE IS
INADEQUATE
FALSE ALTERNATIVE
TYPICAL STRUCTURE:
ONLY TWO ALTERNATIVES ARE GIVEN,
ONE IS REJECTED
THE OTHER ALTERNATIVE IS TRUE
FALLACIES OF CONTEXT
CONT.





POST HOC ERGO PROPTER HOC
“AFTER THIS, THEREFORE BECAUSE
OF IT.”
THE SUPERSTITION FALLACY
STRUCTURES:
A HAPPENED BEFORE B


A CAUSED B
POST HOC, CONT.

SOMETHING HAPPENED IN THE
PAST TO ASSOCIATE A AND B; A
HAPPENED AGAIN



B WILL BE THE RESULT
POST HOC, CONT.

EVERTIME IN THE PAST WHEN I
HAVE DONE X, SOMETHING HAS
HAPPENED, Y . X HAS HAPPENED
AGAIN



Y WILL HAPPEN AGAIN
FALLACIES OF CONTEXT,
CONT.

HASTY GENERALIZATION

THERE IS ONE EXPERIENCE IN
WHICH P IS TRUE


P IS ALWAYS TRUE
FALLACIES OF CONTEXT,
CONT.

COMPOSITION AND DIVISION

COMPOSITION:
P IS TRUE OF ONE PART OF
SOMETHING



P IS TRUE OF THE WHOLE THING
FALLACIES OF CONTEXT, END


DIVISION:
P IS TRUE OF THE WHOLE THING



P IS TRUE OF ONE SPECIFIC PART OF
THING
P.QUIZ 6.3, P. 146.
FALLACIES OF LOGICAL
STRUCTURE

SUBTLE LOGIC ERRORS IN FORM OF
REASONING

BEGGING THE QUESTION
(CIRCULAR)


Structure:
P

P
FALLACIES OF STRUCTURE,
CONT.

Begging the Question, cont.
P

Q

P

Q CIRCLES BACK TO P TO SUPPORT P

FALLACIES OF STRUCTURE,
CONT.

EQUIVOCATION (MANY VOICES)

SWITCHING MEANING OF WORD IN
MIDSENTENCE OR IN ARGUMENT
PLAY ON WORD MEANING
STRUCTURES IN TEXT, P. 150


FALLACIES OF STRUCTURE,
CONT.

APPEAL TO IGNORANCE

TWO STRUCTURES:
P HAS NOT BEEN PROVED FALSE




P IS TRUE
APPEAL TO IGNORANCE,
CONT.

P HAS NOT BEEN PROVED TRUE



P IS FALSE
LEGAL PRINCIPLE: A PERSON IS
INNOCENT UNTIL PROVEN GUILTY
DIVERSION


FORM 1.
PROPOSITION P IS TRUE




PROPOSITION Q IS TRUE
FORM 2.
THERE IS GOOD REASON TO BELIEVE Q IS
TRUE


P IS TRUE
COMMON FORMS OR SPECIES
OF DIVERSION



RED HERRING: USE OF HERRINGS
TO DIVERT THE SMELL OF A HOUND
DOG AWAY FROM THE CRIMINALS
PATH.
STRAW MAN: MISREPRESENTATION
OF ARGUMENT AND POSITION TO
WEAKEN IT AND FIND IT FAULTY.
P.QUIZ 6.4., P. 155.