1.4
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Philosophy
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Dec 6, 2023
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Uploaded by CorporalRockSalamander39
1.4
Logical
Fallacies
Activity
6:
Categorical Propositions
For
the
given categorical propositions,
do
the
following:
a)
If
necessary, rephrase
the
statement
in
standard
form.
b)
Draw
a
Venn
diagram
for
the
proposition
and
label
all
regions of
the
diagram.
c)
Based
only
on
the
Venn
diagram (not
on
any
other knowledge
you
have),
state whether
the
last statement
is
True
or
False.
•
">
Af!.
)
salty
foods
cause high blood
pressure. Apples
do
nofcausehigh
blood pressure,
so
apples
are
not
salty.
\JC,\
t
o\
I
l
:S
0
1...~
v ,
o{
•
swimmers are afraid
of
water.
-
Melissa
is
afraid
of
water,
so
Melissa
must not
be
a swimmer.
\J
ctd
S\)
....
t,"'--'\
• IAiilats
are
gulligJe.
is
gullible,
so
must
be
a
cat.
\V\
u~\\
J
f\
-,J
S""°..Y
t1
"t?'
l
• ~
ovie
stars
are
redhe~s.
Can
you
conclucle
that
there
are
blond
movie
stars?
<>.t
-
"'!Ot
13
-
I
V\
v
~t
ct
rl:J
t
5:);1
al
1.4
Logical
Fallacies
Evaluating
Arguments
Activity 8*: Determine the strength
of
the inductive argument.
James Franco, Jodie Foster, Jennifer Lawrence, and Jack Nicholson have all won Academy Awards for
acting. Actors whose names start with J are bound
to
win an Academy Award.
Activity
9*
:Use a set diagram to determine whether the argument is valid.
If
the argument is valid, determine
if
it is also sound.
a.
"All cats are mammals and a tiger is a cat, so a tiger is a mammal."
First let's write the argument in its "premise, premise, conclusion" form. - - write the first premise as a
qualified proposition
(some, none, all) since this will form the basic structure
of
our diagram.
Premise: all cats are mammals
Premise: a tiger is a cat
Conclusion: a tiger is a mammal
This argument is
____
valid
____
because we were able to show that the conclusion follows
logically from the premises. The argument is also _
___
sound
_____
since the premises "all
cats are mammals" and "a tiger is a cat" are
tr
ue.
b.
"All water bottles are plastic. This is a water bottle, so it must be plastic."
fr
f'IV
\
0
1S
f') :
~ll
vJ
ul~
(
butH
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qf'f
p
\otS
t c
fr
e•··
1
,zr<:
: 7~
,'b
lS.
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b"'.lt+
4
Conc\l,\S~
\)""
·.
iJ.
l'\1
'-,t1J
P
'"'~t
~
c
, r
This argument is
____
true
_____
because we were
__
O_r
---.-'
••
'---
\---,-,,---_to show that the
conclusion follows logically from the premises. The argument is
,\
,1
I\;
fi
because the
premise that all water bottles are plastic is
____
sound___
'"
15
Chapter
1:
Logic
and
Sets
Brooks
MTH
105
c.
"All firefighters know CPR. Jill knows CPR, so Jill must
be
a firefighter."
:Prrn1
,srs
))
~\\
rrr
C
~~
-u
5
\'.:t-
·:.lV
cF
Q..
D
s·
)i\\
\cV'
o\.)~
crR
r
,rt"
ns,
,
C
on
c\
VI
':
))
Q
Y\
J \\ .\
c..
r
1ef'
I
°)
"-
-h'
r
I
Since
we
CJt11
determine which group Jill must be a part of, the argument is
.(
-; ,
. The statement that Jill is a firefighter does not follow logically from the premises
that "all firefighters
know
CPR"
and that "Jill knows CPR". Since the argument is not valid, it
cannotbe
____
sound
__
_
d.
"None
of
my
friends like dancing. Kai
doesn't
like dancing. Therefore, Kai is
my
friend."
.
1
P
rtt\
'\
\
&r-5
:
~
bnf
o-1-
,
{Y)~
f,
~
-fv,
elr
,:y_
r
d°'~
('
1
f\
v
p(C
h
'>
\
S
l)
_'
l
Ci~
cl:f'')h
-\
\
\Gr
d.
u
lfle'i,
1
'1
CJ
v\C
\t-l
)'\
-)\r°\
·•
r
c-'
t
'<;
P
·,
'{
r\
\-fl<\
J
The
conclusion is
__
invalid,
___
.
And is also
___
not
sound.
___
_
e.
"Some
young
adults
make
minim
um
,vage
an
d Tara is a
young
adult.
Therefore,
Tara
makes
minimum
wage."
_
1
,
,.,.
~
1,,.
J
_
1
1.L.
l',
qk.C
t-
'h1\ ,,
,1
l•
'.-
1
,
,\
,;;
:'
,-
_
0\l'
' I!\_
\f';J!J.• 't)
O,b"
-
vllU
\
r
cf
If'' \
ff
s :
·r
C..
(
c-,
' )
C0n
(
\\_]\
s\
;S
A
'_T
0-,
0\
Cl
'f)'v\
~'\.
,
C\
cl
0i
\
\-'
The
conclusion is
____
invalid
______
and
_____
not
sound.
___
_
16
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1.4 Logical Fallacies
Unit
1:
Logic
Section
1.4:
Logical
Fallacies
A
r;,;
~y
is a-type
ofa
~gument
th
--;;
t appears
-
\)C\\\
J
but uses a l~gical error to-persuad; o~ dec-ei ~
Common Logical Fallacies
A
personal attack
argument attacks the person making the argument while ignoring the argument itself.
An
appeal to ignorance
argument assumes something
is
true because
it
hasn't
been proven false.
An
appeal to authority
argument attempts to use the authority
of
a person to prove a claim.
A
false dilemma
argument falsely frames an argument as an "either
or
" choice without allowing for additional
1
options.
A
straw person
argument involves misrepresenting the argument
in
an oversimplified, distorted and less
favorable way to make it easier to attack.
A
post hoc
argument claims that because two things happened sequentially, then the first
must
have
caused
the
second.
Activity 1
*:
Match the arguments below with the logical fallacy.
1.
"Jane says that whales
~en't
fish, but she's only in the second grade so she
can't
be right."
~
c-v-
&)
ro
\
CA
f\
G\
c\(.
2.
"Every morning the rooster crows just before dawn. It must be his crow that makes the sun rise."
Y
o~
\-
h
::)C
3.
"A diet high in bacon can be healthy; Doctor Atkin"s said so."
A
"SJ
?·
Ccl
\
t-o
ov.\~'0\'
.-r
-
v\
4.
"Jane says that whales aren't fish, but every
~~(;;
knows that they're really mammals. She's so stupid."
~~Y'C,\
Oif
tt
t
c~
5.
"Jennifer Hudson and Oprah lost weight with
We
ight
Wa
tchers, so their program must work."
c;
}ro
\J'
l
{)e
r
y\]
\f'
6.
"Senator Khouri has proposed reducing military spending by 10%. Apparently, she wants to leave us
defenseless against attacks by terrorists."
.
_
1
.,..J.l
I/
f
r
r<;_
o r .(?
1
v1
fr(;\
Ct---
7.
"Today I wore a red shirt and my football team won! I need to wear a red shirt every time they play to make
sure they keep winning."
+
VY<:"J
(
8
"M S . h .
11
d
\=7
°
r
h.
d
.
.c.
.
r.
m1t
IS
a co ege ropout, so
IS
stance on e ucation re1orm cannot be trusted."
Ck--
~Y
\
6\
\
~t-C\(
K
9.
"Nobody has proven that phot~ isn't.
of
Big~ot,
so it must be Bigfoot."
OJ~
·
-t>
Ct
\
+-
o
•
<:1
r0
-c
a
i\
Gf
10.
"Either those lights in the sky were an airplane or aliens. There are 'no airplanes scheduled for tonight, so it
must be aliens."
17
\
1
\
Chapter
1:
Logic
and Sets
Brooks
MTH
105
Group
Work:
The Association for Family Values has endorsed Ms. Burke, so you should vote for her.
Fallacy: appeal to authority
a.
Coyotes must be extinct, since I haven't seen any for five years.
Fallacy: appeal to ignorance
b.
"You
don't drink Coke, so you must not consume caffeinated drinks."
Fallacy: false dilemma
Fallacy: appeal to ignorance
c.
"People should avoid seeing the movie
Star
Wars
because Jan was diagnosed with strep throat the
next day after she saw
it,
and I got the flu a few days after seeing that same movie."
Fallacy: post hoc
d.
"The
failing New York Times endorsed
"Mr.
Cheng, but he is a moron who doesn't know
what
he is
doing. Don't vote for him."
Fallacy:
personal attack
Or Create your own Logical Fallacy:
18