Critical Thinking, deductive reasoning, philosophy, truth

1. Truth
A Standard of Critical Thinking

2. Review
Philosophy: the attempt to
answer, critically, the
epistemological, metaphysical,
and ethical questions.
An Issue Question: is a yes-orno question, and is the way to
formulate questions for the
disputed question method
(quaestio disputata).
Principle of Charity: for any
claim, give it the strongest
possible interpretation.
Principle of Sufficient
Reason: for any claim, give
reason why it is true, or not.
A virtue is an excellence, a
mean between two extremes
called vices.

3. Review
The Disputed Question Method
yes:
Reasons supporting
the yes answer or
refuting the no answer.
Which side
has the better
reasons?
the question
no:
Reasons supporting
the no answer or
refuting the yes
answer.

4. Truth
What is the
difference
between the
truth, an honest
mistake, and a
lie?

5. Truth
Four Types of Truth
Matters of Taste or Opinion
Matters of Convention
Matters of Fact
Matters of Necessity

6. Truth
Four Types of Truth
Matters of Taste or Opinion
Matters of Convention
Matters of Fact
Matters of Necessity
The ocean is prettier than the desert &
The desert is prettier than the woods.

7. Truth
Four Types of Truth
Matters of Taste or Opinion
Matters of Convention
Matters of Fact
Matters of Necessity
The desert is prettier than the woods &
The woods are prettier than the ocean.

8. Truth
Four Types of Truth
Matters of Taste or Opinion
Matters of Convention
Matters of Fact
Matters of Necessity
Can be indexed to a person, place,
time or culture:
According to Alex pizza is better
than pot stickers.
>
Does this exhaust all truths?

9. Truth
Four Types of Truth
Matters of Taste or Opinion
Matters of Convention
Matters of Fact
Matters of Necessity
Consider
someone who
honestly believes
red means go and
green means stop.
Is his belief true,
or an honest
mistake?

10. Truth
Four Types of Truth
Matters of Taste or Opinion
Matters of Convention
Matters of Fact
Matters of Necessity
Steering wheels are on the left.

11. Truth
Four Types of Truth
Matters of Taste or Opinion
Matters of Convention
Matters of Fact
Matters of Necessity
Steering wheels are on the right.

12. Truth
Four Types of Truth
Matters of Taste or Opinion
Can be indexed to a convention, culture
or society:
According to the music business,
Tupac is gangsta while My Chemical
Romance is emo.
Matters of Convention
Matters of Fact
Matters of Necessity
Does this exhaust all truths?

13. Truth
Four Types of Truth
Matters of Taste or Opinion
Matters of Convention
Matters of Fact
Matters of Necessity
Consider a world
without people
or conventions,
would water still
boil at the
temperature we
call 212º
Fahrenheit?

14. Truth
Four Types of Truth
Matters of Taste or Opinion
Matters of Convention
Matters of Fact
Matters of Necessity
The earth is 93 million miles from the sun.
—Some think this fact is contingent—

15. Truth
Four Types of Truth
Matters of Taste or Opinion
Matters of Convention
Matters of Fact
Matters of Necessity
Water boils at 212º fahrenheit.
—Some think this fact is contingent—
it could have been otherwise

16. Truth
Four Types of Truth
Matters of Taste or Opinion
Such truths as often expressed ceteris
paribus:
The earth is about 93 million miles
from the sun on average.
Water boils at 212º fahrenheit at
standard barometric pressure.
Matters of Convention
Matters of Fact
Matters of Necessity
Does this exhaust all truths?

17. Truth
Four Types of Truth
Matters of Taste or Opinion
Matters of Convention
Matters of Fact
Matters of Necessity
Consider a
world with
different
natural laws,
would
1 + 1 = 2?

18. Truth
Four Types of Truth
∏
=
3.141592...
Matters of Taste or Opinion
π needs to be exact for a circle to be round
Matters of Convention
1
Matters of Fact
Matters of Necessity
+
1
=
2
simple arithmetic is the way things are
—Most think these facts are necessary—
they could not have been otherwise

19. Truth
Four Types of Truth
Matters of Taste or Opinion
Matters of Convention
Matters of Fact
Matters of Necessity
∏
=
3.141592...

20. to pursue the truth of a claim
avoid matters of taste, fill in the
indices, and spell out the ceteris
paribus.

21. Truth is when a claim
matches what is.

22. Claims are candidates for
truths, such as beliefs stated
in language.
Romeo and Juliette is a
tragedy.
The jellyfish has tentacles.
Eleven is a prime
Drinking milk is healthy.
The music is loud. number.
Same-sex schools are optimal.
Jupiter is bigger than Mars.
Hockey is better than basketball.
Jacqui thinks black is more alluring than pink.
New York is the largest city in the US.
The child looks at the jellyfish.
The Constitution of the United States was adopted on September 17, 1787

23. Truth
The jellyfish has tentacles.
Why is this true?

24. Meaning
Intensions— the concept that meanings
are things with properties and in
relations

25. Truth
How a claim matches what is.
The jellyfish
has tentacles.
Because the thing
designated by the subject
has the property expressed
by the predicate.

26. The Disputed Question Method
Applied to Truth
Reasons supporting
the yes answer or
refuting the no answer.
yes:
Does the thing designated
by the subject have the
property expressed by the
predicate?
no:
Which side
has the better
reasons?
Reasons supporting
the no answer or
refuting the yes
answer.

27. to evaluate the truth of a claim
determine whether the thing
designated by the subject has the
property expressed by the
predicate

28. Truth
The child looks at the
jellyfish.
Why is this true?

29. Truth
looks at
How a claim matches what is.
the jellyfish.
The child
The things designated by
the nouns stand in the
relation expressed by the
predicate.

30. The Disputed Question Method
Applied to Truth
Reasons supporting
the yes answer or
refuting the no answer.
yes:
Do the things designated
by the nouns stand in the
relation expressed by the
verb.
no:
Which side
has the better
reasons?
Reasons supporting
the no answer or
refuting the yes
answer.

31. to evaluate the truth of a claim
determine whether the things
designated by the nouns stand in
the relation expressed by the
verb.

32. Truth
When a claim matches what is: two forms
subject–Predicate Form
subject–Verb–object Form
((subject) Predicate)
((subject) Verb(object))
designates/expresses
designates/expresses/designates
<<thing> property>
<<thing> relation<thing>>

33. Truth
When a claim matches what is: subject/Predicate form
The Claim
The sun’s gravity well bends light.
What is: reality
<bending light>
((The sun’s gravity well) bends light.)
((subject) Predicate)
designates/expresses
<<thing> property>
<the sun’s
gravity well>

34. Truth
When a claim matches what is: subject/Verb/object form
The Claim
What is: reality
The remora is on the shark.
<shark>
((The remora) is on (the shark)).
((subject) Verb(object))
designates/expresses/designates
<<thing> relation<thing>>
<being on>
{
<remora>

35. Meaning
What is: things with properties and in relations
((subject) Predicate)
((subject) Verb(object))
designates/expresses
designates/expresses/designates
<<thing> property>
<<thing> relation<thing>>
Meanings as intensions

36. Meaning
Extension— the concept that meanings
are sets and their members

37. Meaning
Meanings minus things: concepts (or properties and relations)
Meanings
Thing
horse
fast things
Equidae
four legged things
land animal
mammal
Seabiscuit
animal
+
Concept
_____is an Equidae.
_____is four legged.
_____is bigger than_____.
_____is a horse.
_____is fast.
_____is an animal.
_____is faster than_____.

38. Concepts
General and Specific
A wavelength of light
is an electromagnetic phenomenon.
A color is a wavelength of light.
Red is a color.
The cherries are red.

39. Concepts
General and Specific
Red as a thing.
A wavelength of light
is an electromagnetic phenomenon.
A color is a wavelength of light.
Red is a color.
The cherries are red.
Red as a concept.

40. Concepts
General and Specific
Color as a thing.
A wavelength of light
is an electromagnetic phenomenon.
A color is a wavelength of light.
Red is a color.
The cherries are red.
Color as a concept.

41. Concepts
Linking the General to the Specific
The cherries are red.
more abstract
more concrete
more concrete
Red is a color.
more specific
more specific
A color is a wavelength of light.
more general
A wavelength of light
is an electromagnetic phenomenon.

42. Concepts
Have Extensions
being a vowel
Properties
as
Concepts
M
X
N
D
C
L
Y
V
B
F
E
A
R
Q
O
W
P
S
I U
H
G
K
J
Z
T

43. Concepts
Have Extensions
being divisible by two without a remainder
Relations
as
Concepts
9
3
22
1
1
21
32
14
77
27
66
144
13
5

44. to evaluate the truth of a claim
determine whether the things
designated by the nouns are in
the extension of the verb.

45. The Disputed Question Method
yes:
Reasons supporting
the yes answer or
refuting the no answer.
Are the things designated
by the nouns are in the
extension of the verb?
no:
45
Which side
has the better
reasons?
Reasons supporting
the no answer or
refuting the yes
answer.

46. Definitions
Ambiguity: The Problem of Multiple Meanings
Names can be ambiguous:
Jupiter
Mary

47. Definitions
Ambiguity: The Problem of Multiple Meanings
Other terms can be ambiguous:
fire
green

48. Ambiguous applies to terms
with more than one
meaning.

49. Definitions
Vagueness: the Problem of Unclear Extensions
Many terms can be vague:
pile – how many make a pile?
bald – how many hairs
before you stop being bald?

50. Definitions
Vagueness: the Problem of Unclear Extensions
being a vowel
is y in the
extension of
being a
vowel?
M
X
N
D
C
L
Y
V
B
F
E
A
R
Q
O
W
P
S
I U
H
G
K
J
Z
T

51. Vague applies to terms with
unclear extensions.

52. Definitions
Ambiguity and Vagueness
Some Terms Can Be Both
Ambiguous and Vague—
Try to come up with some:

53. to define a term
give it one clear meaning

54. Definitions
Claims with terms as things

55. Definitions
Claims with terms as things
Subject
‘claim’
Predicate
means an assertion open to challenge
term
meaning
<Thing>
<Property>

56. The Disputed Question Method
Reasons supporting
the yes answer or
refuting the no answer.
yes:
Do the things in the
extension of the term being
defined have the property
expressed by the meaning?
no:
Which side
has the better
reasons?
Reasons supporting
the no answer or
refuting the yes
answer.

57. Definitions
Stipulating definitions
Make up your own terms that
you might characterize as words
that aren’t in the dictionary but
should be.

58. Definitions
Stipulating definitions
Sniglets*
Words that don't appear in the dictionary, but should.
Aeroma (ayr oh' ma) - n. The odor emanating from an exercise room after
an aerobics workout.
Aeropalmics (ayr o palm' iks) - n. The study of wind resistance conducted
by holding a cupped hand out the car window.
Anaception (an a sep' shun) - n. The body's ability to actually affect
television reception by moving about the room.
Animalanche: When you kick your stuffed animals in your sleep and they
fall all over you or the floor. (from Kaffit, age 9)
Aquadextrous - adj. Possessing the ability to turn the bathtub faucet on and
off with your toes.

59. Definitions
Stipulating definitions
Sniglets show that we may prescribe or stipulate a definition for
how a term ought to be used.
The examples from the dictionary show that we may describe or
designate a definition for how a term is actually used.
In this class we will prescribe or stipulate technical definitions
for how terms ought to be used.

60. Normative definitions
which prescribe or stipulate
how a term ought to be
used.

61. Normative claims which
prescribe or stipulate how
things ought to be.

62. Descriptive definitions
which describe or designate
how a term is actually used.

63. Descriptive claims which
describe or designate how
things actually are.

64. Law of Assumption—
assume anything at any
time.

65. Law of Assumption—
assume anything at any
time.
Sniglets are an example of
applying this law.

66. Law of Assumption—
assume anything at any
time.
Thought experiments are
based on assumptions.

67. Law of Assumption—
assume anything at any
time.
Critical Thinking has
techniques to reject faulty
assumptions.

68. define key terms
key terms are terms needed for the
claim to be evaluated as true or
false, they are terms whose
properties or relations need to be
specified or whose extensions need
to be clarified.

69. define technical terms
technical terms are terms needed for
critical thinking, such as truth,
charity, and reason.

70. The Standard of Truth—accept
only those claims and
definitions that have the best
reasons for being true.

71. Assignment
How do you define
contradictions?
Consistency
Read the cases and list the
contradictions you find.
How do you tell when a
conjunction is false?