Transcript Document 7376693

Critical Thinking
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Critical thinkers use reasons to back up their
claims.
What is a claim?
◦ A claim is a statement that is either true or false.
It must ALWAYS have a truth value (although we
do not always have to know if it is true or false).
Here are some examples of claims:
 It is 5 p.m.
 It ought to be easier to register for classes at this
university.
 2 + 2 =4
 There is ice on the moon.
 There isn’t ice on the moon.
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Truth or falsity do not apply to questions,
commands, or exclamations. Hence, they are
not claims.
Wow!
Will you please close the door?
Keep your eyes on your own paper.
These are not claims.
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An argument =df. An attempt to support a
claim representing a certain position on an
issue by providing other claims that serve
as a reason or reasons for believing it.
The conclusion (of an argument) = df. The
claim (position on an issue) one is
attempting to support, or the claim for
which one is arguing.
The premises (of an argument) = df. The
claims that serve as reasons for believing
the conclusion.
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Thus an argument is a set of claims that
involves the relations of claims to one
another.
The relations between an argument’s claims
are that the premises support the
conclusion or that the conclusion follows
from the premises.
The recognition, construction, evaluation,
and, where necessary, criticism of
arguments is a crucial part of critical
thinking.
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In critical thinking, an argument is not about
two people having a feud or disagreeing
about something. Arguments, in the critical
thinking sense, do not even need two people.
“Arguments are attempts to persuade”
◦ While arguments may be used for this purpose
not all arguments attempt to persuade and not all
attempts to persuade are arguments.
◦ The better view is that arguments are attempts to
prove or establish or support some claim.
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“Arguments are attempts to explain.”
◦ Arguments and explanations do have a superficial
resemblance but their purposes are different.
◦ An argument attempts to establish that some
claim is true whereas an explanation attempts to
specify either how something works or what
caused or brought it about.
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Philosophers traditionally classify arguments as
either deductive or inductive.
The difference between a deductive and an
inductive argument is the difference in the sort of
claim made for the argument.
If the arguer alleges that the premises are
conclusive evidence for the conclusion, then the
argument is deductive; if the assertion is that they
support the conclusion but don’t guarantee it, then
the argument is inductive.
Deductive arguments are either valid or invalid.
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To say that a deductive argument is valid is to say
that it is not possible for its conclusion to be false
if its premises are true. Thus we define validity as
follows: A deductive argument is valid when, if its
premises are true, its conclusion must be true.
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Every deductive argument makes the claim that its
premises guarantee the truth of its conclusion, but
not all deductive arguments live up to that claim.
Deductive arguments that fail to do so are invalid.
An example of a valid argument:
◦ P1:f you get 90% or above in this class, then you will get an
A in the class.
P2: You got 90% in this class.
Conclusion: Therefore you will get an A in the class.
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Inductive arguments are those in which the
premises are intended to provide support, but not
conclusive evidence, for the conclusion.
Inductive arguments are not valid or invalid.
Inductive arguments are weak or strong.
An inductive argument is strong when its premises
provide evidence that its conclusion is more likely
true than false. An inductive argument is weak
when its premises do not provide evidence that its
conclusion is more likely true than false.
Paying off terrorists in exchange for hostages is
not a wise policy, since such action will only lead
them to take more hostages in the future. This is
an inductive argument.
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As we already said, an argument, whether
deductive or inductive, has two parts, and
one part is the reason for believing that the
other part is true. Sometimes there are
indicators to help us figure out which part is
which. Unfortunately, indicators are not
always used. However, it is very helpful to
understand the language of arguments.
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A few examples of conclusion indicators
(from page 15):
Therefore
Thus
Hence
So
Consequently
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A few examples of premise indicators (from
page 16):
Since
For
Because
Given
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Newton was an abstract thinker because all
scientists are abstract thinkers and Newton
certainly was a scientist
What is the conclusion? What are the premises?
Every officer on the force has been certified, and
nobody can be certified without scoring above 70
percent on the firing range. Therefore every
officer on the force must have scored above 70
percent on the firing range.
What is the conclusion what are the premises?
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Truth –
What is truth?
◦ In philosophy, there are very many theories of truth.
If you take an introduction to philosophy course, for
example, you will probably learn about coherence
theories of truth, correspondence theories of truth,
pragmatic theories of truth, and so on.
◦ We are taking a basic approach to truth in this
class. Truth and falsity are the properties of claims,
and, generally speaking, a claim has whichever
property it has, regardless of what we think about
this. The claim is true if it corresponds with reality,
basically.
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What is knowledge?
David L. Fairchild said, ““This claim may be less
extreme than it first appears, Part of what is at
issue here involves a distinction between
appropriate and inappropriate ways of using
“know.” We sometimes claim to “know” things that
we only believe, for example, or things that we
wish we knew or that we would like someone else
to stop talking about. Sometimes we use “know”
deliberately, to preclude further discussion of a
topic about which we are unsure of or with which
we are uncomfortable. If becoming better
reasoners entails becoming more precise in our
epistemological vocabulary, we may well claim the
result of “knowing” less after the experience than
we did before. “
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For the purpose of this class, we will say that
you can have knowledge of the truth of a
claim if (1) You have a belief (2) You have
justification for this belief in the form of an
argument beyond a reasonable doubt (3) You
have no reason to expect that you are
mistaken.
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Value judgments – What are value judgments?
What is the difference between a difference in
values and a difference between tastes or
preferences?
How can critical thinking be related to value
judgments?