Arguments in Philosophy
Introduction to Philosophy
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Arguments
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Philosophy is the art of constructing and
evaluating arguments
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It’s all about the argument
Arguments are meant to be convincing
So philosophers must be sensitive to what
makes an argument convincing
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Or not
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Thinking Critically
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First step: Think Critically
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What is the argument trying to say?
Why does the argument succeed, or not?
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The form of the argument
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What’s good, bad, or indifferent?
What’s the point?
How do we get to the point?
Structure
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How do the parts of the argument fit together?
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General Structure
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In general, arguments consist of:
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The thesis or position argued for
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The reasons why the conclusion should be
accepted
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The conclusion
The premises
Usually this is written in “standard form”:
Premise 1 (Justification)
Premise 2 (Justification)
Therefore, Conclusion (Justification)
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Two kinds of argument
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In general, there are two kinds of argument:
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Deductive Arguments
Inductive Arguments
These arguments work (slightly) differently,
so they’re evaluated differently
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But let’s be more specific…
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A statement is any unambiguous declarative sentence
about a fact (or non-fact) about the world.
 It says that something is (or isn’t) the case.
An argument is a series of statements meant to
establish a claim.
A claim or conclusion is the statement whose truth an
argument is meant to establish.
A statement’s truth value is either true or false.
 All statements have a truth value. A statement is false
when what it says about the world is not actually the
case. A statement is true when what it says about the
world is actually the case.
A premise is a statement that is used in an argument
to establish a conclusion.
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Deductive Arguments
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A deductive argument is:
VALID if its premises necessarily lead to its
conclusion.
 That is, if you were to accept that the premises are all
true, you must accept that the conclusion is true.
SOUND if it is valid and you accept that all its
premises are true.
A good, convincing argument is sound.
 A bad argument is any other kind of argument.
VALIDITY + TRUE PREMISES* = SOUND
 *or, at least, accepted premises
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Examples
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All people are mortal. Socrates is a person.
Therefore, Socrates is mortal.
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All people are mortal. My dog is mortal. Therefore,
my dog is a person.
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Invalid.
Oranges are green. All green things make me sick.
Therefore, oranges make me sick.
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Sound
Valid. Not sound.
Whales know how to play hockey. Therefore,
Canadians like winter.
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Invalid.
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Notice…
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Validity does not depend on the truth of the
premises.
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All people are mortal. My dog is mortal.
Therefore, my dog is a person.
The premises are true. But the argument is still
invalid.
Soundness does not depend on the truth of
the conclusion.
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An argument can be bad even if the conclusion is
obviously true.
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Evaluating Deductive Arguments
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Good arguments must be sound.
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If you want to accept of an argument, you would
have to show both validity and soundness
Bad arguments can be bad in two ways:
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Invalid
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You can show that the conclusion does not follow from
the premises
Unsound
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You can show that at least one premise is unacceptable
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Inductive Arguments
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Inductive arguments are not truth preserving
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Even in a good inductive argument where the
premises are true, the conclusion does not have
to be true.
At most, the conclusion is most likely true.
Inductive arguments are meant to make
conclusions more likely or more acceptable.
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Inductive Arguments
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An inductive argument is:
STRONG if its premises make the conclusion
probable
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That is, if you were to accept the premises as true, then
you would have to accept that the conclusion was probably
true
COGENT if it is strong and its premises are
accepted
A good, convincing argument is cogent.
STRENGTH + TRUE PREMISES* = COGENT
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Examples
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This cooler contains 30 cans. 25 cans selected at
random contained soda. Therefore, all the cans
probably contain soda.
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This cooler contains 30 cans. 3 cans selected at
random contained soda. Therefore, all the cans
probably contain soda.
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Cogent
Weak
Every monkey I’ve seen (over 500) has blue teeth.
Therefore, the next monkey I see will probably have
blue teeth.
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Strong, but not cogent
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Notice…
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Strength admits of degrees.
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An argument can be stronger or weaker
Usually, the more evidence available, the stronger
the argument
Strength does not depend on the truth of the
premises
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Evaluating Inductive Arguments
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Good arguments must be cogent.
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If you want to accept of an argument, you would
have to show both strength and cogency
Bad arguments can be bad in two ways:
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Weak
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You can show that the premises does not make the
conclusion more probable
Not cogent
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You can show that at least one premise is unacceptable
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Argument by Analogy
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One particular kind of inductive argument is
an Argument by Analogy
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Comparison of two or more things
Concludes that they share characteristic(s)
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Example:
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Because they share other characteristic(s)
Watches exhibit order, function, and design. They were
also created by a creator. The universe exhibits order,
function, and design. Therefore, the universe probably
was created by a creator.
Evaluated like other inductive arguments
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In Practice…
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Identify the conclusion
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Identify the premises
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What is the claim?
How is the claim supported?
Often, we first have to get rid of anything unnecessary –
mere rhetorical flourishes, repetitions, and irrelevancies.
Reformulate the argument
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Try to put it into standard form
Often, we’ll have to add premises that are implied but not
stated.
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In Practice…
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Identify the form of the argument
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How are the premises supposed to lead to the
conclusion?
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Deductive? Inductive?
Assumptions? Subarguments?
(This will help us add/delete premises)
Evaluate the argument
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Valid? Sound?
Strong? Cogent?
WHY?
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Example
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For Death is to be as it were nothing, and to be
deprived of all sensation... And if no sensation
remains, then death is like a dreamless sleep. In
this case, death will be a blessing. For, if any one
compares such a night as this, in which he so
profoundly sleeps as not even to see a dream, with
the other nights and days of his life, and should
declare how many he had passed better and more
pleasantly than this night, I think that not only a
private man, but even the great king himself, would
find so small a number that they might be easily
counted.
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Example
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For Death is to be deprived of all sensation...
if no sensation remains, then death is like a
dreamless sleep. ...death will be a blessing.
...if any one compares such a night [of sleep
without dreams]... with the other nights and
days of his life, and should declare how many
he had passed better and more pleasantly
than this night, I think.. [he] would find so
small a number...
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Example
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Death is to be deprived of all sensation.
If no sensation remains, death is like a
dreamless sleep.
Anyone will consider a dreamless sleep
better than most days and nights.
--Death is a blessing.
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Example
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Death is to be deprived of all sensation.
If no sensation remains, death is like a dreamless
sleep.
Death is like a dreamless sleep.
Anyone will consider a dreamless sleep better than
most days and nights.
Anyone will consider death better than most days
and nights.
Anything that is better than most days and nights
is a blessing.
--Death is a blessing.
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Example
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Death is to be deprived of all sensation. (Assumption)
If no sensation remains, death is like a dreamless sleep.
(Assumption)
Death is like a dreamless sleep. (Conclusion from 1 and 2)
Anyone will consider a dreamless sleep better than most days
and nights. (Assumption)
Anyone will consider death better than most days and nights.
(Conclusion from 3 and 4)
Anything that is better than most days and nights is a blessing.
(Assumption)
--Death is a blessing. (From 3, 5, and 6)
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