Transcript Philosophy 201 Clark Wolf Iowa State University Spring 2013

Philosophy 201
Clark Wolf
Iowa State University
Spring 2013
Philosophy 201: Syllabus

Be sure you can access on-line version of
the syllabus! (It will be available this
evening at the URL listed.)

Required Text:
Other sources
available on line.

Philosophy 201

Assessment: (Quantitative)





Daily Argument Analysis Exercise, or
occasional quiz at the beginning of class.
Brief Writing Assignment (10%)
Midterm/Final Exams (40% / 45%)
Optional Extended Writing Assignment
Other Considerations: Attendance,
Preparation, Any occasional homework
notices.
Philosophy 201:

Argument Analysis Exercises: We will
typically start class– the first five minutes–
with a short exercise. I will put a prose
argument on screen, and your job will be
to analyze it, identifying the claim to be
supported and the evidence given for that
claim. I will collect these at 10:05, and we
will briefly discuss the answers. If you do
not turn in a 3X5 index card at this time,
you will be marked ‘absent’ from class for
that day.
Philosophy 201

Objectives:


Why study philosophy?
How should Intro Philosophy be organized?
History?
 Topics?


What should you expect to gain from this
class?
Philosophy 201:

Skills



Ability to recognize, analyze, and evaluate
arguments.
Ability to read and understand complex texts.
Ability to think clearly and articulate
alternative perspectives on several important
philosophical questions
Philosophy 201

History of Ideas and Figures:










Plato
Aristotle
Epicurus
Epictetus
Sextus Empiricus
Rene Descartes
Arthur Schopenhauer
John Stuart Mill
William James
…
Philosophy 201:

Topics:






What can we know?
What goals are worth pursuing in life?
What kinds of things exist?
Is there evidence for the existence of God?
What is justice? When can the state
appropriately limit people’s liberty?
Does life– my life– have meaning?

First Reading Assignment:
“Notes on Logic and Critical Thinking”
Available on line-- to be linked from the on-line
version of the syllabus.
Reasoning and Argument Analysis
Clark Wolf
Director of Bioethics
Iowa State University
[email protected]
Argument for Analysis:

Don’t worry too much about these
arguments– do the best you can. The
purpose is to get practice, not to punish
conscientious attempts.

The arguments will get harder
(sometimes) as the semester moves
forward.
Argument for Analysis:
Please provide an interpretation of this argument in STANDARD FORM on a 3X5
index card, with your name on it, and turn it in at 10:05.
“Thoughtless people think that gun control laws will make us
safer, but such laws are a stupid way to ‘protect the public.’
Criminals don’t obey the law, so they will have guns whether or
not these laws are in place. But law abiding citizens who do
obey the law would be disarmed by these laws: If we have
guns, we can protect ourselves, but if we’re denied them we’re
at the mercy of those who have them! If criminals have guns,
it’s better– the public is safer-- if other people also have guns!
Then they have at least a fighting chance. In the end, these silly
laws make us less safe, not more safe. They make it safer for
the criminals, who can be assured that we’re unarmed, but less
safe for the rest of us who can no longer defend ourselves.”
OBJECTIVES: On completion of this unit,
students should be able…
1.1 …to recognize when they are presented with an argument,
1.2 …to analyze arguments by identifying the conclusion and
distinguishing conclusions from premises.
1.3 …to evaluate arguments by considering the plausibility of the
premises and the extent to which the premises support the
conclusion.
1.4 …to distinguish deductive and inductive arguments,
1.5 …to distinguish an argument’s content from its form.
1.5 …to define key concepts: argument, premise, conclusion, evidence,
rationally persuasive argument, fallacy, valid argument, invalid
argument, inductive argument, abductive argument.
1.6 …to evaluate arguments, by (i) distinguishing premises from
conclusion, (ii) putting the argument in standard form, (iii)
critically examining the premises, and (iv) evaluating the
inference from premises to conclusion.
1.7 …to be self-reflectively critical of their own arguments and those of
others.
What is an Argument?
Argument: A set of statements, some of which serve as premises,
one of which serves as a conclusion, such that the premises
purport to give evidence for the conclusion.
Premise: A premise is a statement that purports to give evidence for
the conclusion.
Evidence: To say that a statement A is evidence for another
statement B is to say that if A were true, this would provide some
reason to believe that B is true.
Conclusion: The statement in an argument that is supposedly
supported by the evidence.
When do we encounter arguments?

Any time anyone tries to persuade you of
something, or to make you change your mind.
Rational persuasion uses reasons, but even
irrational persuasion employs reasons (bad
reasons). In evaluating arguments, we need to
be able to evaluate reasons and patterns of
reasoning.

Arguments can be used to persuade, inform,
and investigate.

They can also be used to bamboozle,
confuse, and frustrate.
Example: from “Thank you for Smoking!”
 http://www.youtube.com/watch?v=DrnZdFFovBE

Nick: OK, let’s say you’re defending chocolate and I’m
defending vanilla. Now if I were to say to you “vanilla is the
best flavor ice cream,” you’d say…?
Joey: No, Chocolate is.
Nick: Exactly. But you can’t win that argument. So, I’ll ask
you, “So you think chocolate is the end all and be all of ice
cream, do you?
Joey: It’s the best ice cream. I wouldn’t order any other.
Nick: Oh, so it’s all chocolate for you, is it?
Joey: Yes, chocolate is all I need.
Nick: Well, I need more than chocolate. And for that matter, I
need more than vanilla. I believe that we need freedom,
and choice when it comes to our ice cream, and that, Joey
Naylor, that is the definition of liberty.
Joey: But that’s not what we’re talking about.
Nick: Ah, but that’s what I’m talking about.
-from “Thank you for Smoking” (Film)
Joey: But that’s not what we’re talking about.
Nick: Ah, but that’s what I’m talking about.
Joey: But you didn’t prove that vanilla is the best.
Nick: I didn’t have to. I proved that you are wrong,
and if you’re wrong, I’m right.
Joey: But you didn’t convince me.
Nick: I’m not after you, I’m after them. (pointing to
the crowd around them)
-from “Thank you for Smoking” (Film)
Rational Argument v.
Persuasive Rhetoric

Sometimes people are persuasive not
because they are offering well-reasoned
arguments, but because they are good at
bamboozling other people.

Good philosophical arguments should be
rationally persuasive.
Indicator Words:

Indicator words: Sometimes writers use language that
indicates the structure of the argument they are giving.
The following words and phrases indicate that what
follows is probably the conclusion of an argument:
Conclusion Indicators:





Therefore…
thus…
for that reason…
hence…
it follows that…
Premise Indicators:
Because…
 Since…
 For…
 For the reason that…

Examples:
Since private business is the most effective
instrument of economic change, the government
should utilize the resources of private business
in its economic planning and decision making.
Women work just as hard as men and are just
as productive. Therefore they should be
compensated the same.
Example:

“Because animals are conscious, capable
of experiencing pain and pleasure, they
are like people in significant respects.
Since they are also intelligent—often far
more intelligent than newborn babies for
example, it follows that they deserve kind
treatment from human beings and that it is
wrong to treat them with cruelty.”
Standard Form

Standard Form: Usually we find arguments
expressed in ordinary prose. But as noted,
when we are evaluating arguments it is a good
idea to separate the premises from the
conclusion, and to put the argument into
“standard form.” We say that an argument is in
standard form when the premises are
numbered and listed separately, and when the
conclusion is clearly written underneath them.
Example:

“Because animals are conscious, capable
of experiencing pain and pleasure, they
are like people in significant respects.
Since they are also intelligent—often far
more intelligent than newborn babies for
example, it follows that they deserve kind
treatment from human beings and that it is
wrong to treat them with cruelty.”
Standard Form Version:
(1) Animals are conscious.
(2) Animals are capable of experiencing pain and
pleasure.
(3) Animals are intelligent.
(4) Animals are like people in significant respects.
Conclusion:
(5) Therefore (i) animals deserve kind treatment from
humans and (ii) it is wrong to treat animals with cruelty.
A Reservation:
Whenever we put an argument in standard
form, we have given an interpretation of
that argument. Ideally, an interpretation
should accurately capture the meaning of
the original, but it is always possible to
challenge the accuracy of an
interpretation.
Evaluating an Argument:
“By splicing genes into crop plants, scientists
have changed these crops in ways that never
could have come about through the natural
process of selective breeding. These changes
in our food crops threaten the health of
everyone in the world, and impose a great
danger of massive environmental damage.
Genetically modified crops are unnatural and
dangerous. We should avoid using them and
growing them, and should do whatever it takes
to eliminate them from Iowa farms.”
Questions:
What is the author of this passage trying
to persuade you to believe? (What’s the
conclusion?)
 What reasons are being offered? (What
are the premises?)
 In this argument there are few indicator
words used, but it is not hard to figure out
what the author would like us to believe.

What’s the Conclusion?

Conclusion: Often the conclusion of an argument is
stated either in the first sentence of a paragraph, or in
the last sentence of the paragraph. In this case, the
conclusion—the claim the author intends to persuade us
to accept—is a complex claim. The author urges that:

(1) We should avoid using and growing genetically
modified crops, and
(2) We should do “whatever it takes” to eliminate these
crops from Iowa farms.

What’s evidence or reasons are given?

Premises:
P1) Gene splicing changes crops in ways that could never
have come about through selective breeding.
P2) Changes in food crops due to gene splicing threaten
everyone’s health.
P3) Changes in food crops pose a threat of massive
environmental damage.
P4) Genetic modification of crops is unnatural.
P5) Genetic modification of crops is dangerous.
Step One: Are the premises true?

Premise 1: Gene splicing changes crops in ways that
never could have come about through selective
breeding.

Evaluation: Is this true? Some of the properties that
have been induced through genetic engineering might
have been produced through selective breeding. But it
is unlikely that the genetic alterations that have been
effected in the production of genetically modified crops
would have been produced in any other way. Perhaps
this premise should be somewhat qualified, but it
contains a kernel of truth.
Step One: Are the premises true?

Premise 2: “Changes in food crops due to gene
splicing threaten everyone’s health.

Evaluation: This claim requires additional
support and evidence. Many people are
concerned about the health effects of genetically
modified food crops, but no one has shown that
these crops are dangerous. The author of the
paragraph provides no evidence that genetically
modified crops are dangerous.
Step One: Are the premises true?

Premise 3: Changes in food crops pose a threat
of massive environmental damage.

Evaluation: Once again, this claim requires
support. There may indeed be reasons for
concern about the environmental effects of
genetically modified crops, but the author has
not given us any evidence. Without more
evidence, we may not be in a position to
evaluate this premise.
Step One: Are the premises true?

Premise 4: Genetic modification of crops is
unnatural.

Evaluation: The term ‘natural’ can be slippery,
and we may need to know more about what the
author has in mind. In context, it seems that the
author regards things that are ‘unnatural’ as
bad. But in an important sense, bridges,
computers, vaccines and artworks are
“unnatural.”
Step One: Are the premises true?

Premise 5: Genetic modification of crops is
dangerous.

Evaluation: Once again we need evidence for
such a claim before we can place our trust in it.
In what sense is genetic modification
dangerous, and what are the specific dangers
the author has in mind? Without more evidence,
we may simply find that we are not yet in a
position to evaluate the argument.

Step Two:
If the premises were true, would they
provide good evidence for the
conclusions?
 Are there implicit premises that should
be included in the evaluation of the
argument?


A Strategy for Evaluating Arguments: Of course, for the
purposes of this course, your views about GM crops are not
what matter. What does matter is the strategy used here for
evaluating the argument under consideration:

First, identify the argument’s premises, and restate them
clearly.

Second, evaluate each premise individually: is it true or false?
What evidence, what information would you need to know in
order to determine whether the premises are true?

If you discover that the premises of the argument are simply
false, you may need to go no further. But if the premises seem
true, there is a third important step to take in evaluating the
argument:

Third, consider the relationship between the premises and the
conclusion. What kind of argument is it? Is it a good argument
of its kind?
Argument for Analysis:
“Different cultures have different moral values:
For example, some cultures hold that it’s morally
right to ethnically cleanse the nation by killing
those who are not members of the dominant
group. Some cultures hold that terrorism is
morally praiseworthy, while others believe that it’s
wrong to harm innocent people. But no one is in a
position to say that their values are better than the
cultural values of any other group. Because of
this, it is inappropriate for us to impose our
arbitrary cultural values on terrorists or ethnic
cleansers whose values are different from ours.”
In Standard Form:
1) Different cultures have different moral values.
[For example, some cultures hold that it’s morally right to ethnically cleanse the nation by killing those
who are not members of the dominant group. Some cultures hold that terrorism is morally
praiseworthy, while others believe that it’s wrong to harm innocent people.]
2) No one is in a position to say that their values are better
than the cultural values of any other group.
3) Our own values are arbitrary, and we are unjustified in
giving them special weight.
(Implied premise?)
4) Conclusion: It is inappropriate for us to impose our
arbitrary values on terrorists or ethnic cleansers whose
values are different.
Thoughts on this Argument:

If this argument goes wrong, where does it go wrong? Is it intolerant
to prevent people from harming one another?

Is ‘harmfulness’ an intercultural value that allows us to make
judgments about the value systems of different cultural groups?

The argument concludes with a plea for tolerance: Should we be
tolerant of all differences? Is it ‘intolerant’ to prohibit theft and
assault, since thieves and assailants clearly don’t share the values
that motivate our legal system. What are the limits of tolerance, and
how can we justify these limits?

What is the relationship between ‘relativism’ and ‘toleration?’ If one
is a relativist, would one be tolerant of others? What if ‘tolerance’ is
not one of the values one’s own culture recommends? Are we
tolerant when we permit others to harm and oppress?
Fallacies:

Fallacy: An argument that provides the
illusion of support, but no real support, for
its conclusion.
A few fallacies:
Ad hominem- attacking the person
instead of addressing the argument.
 Ad bachilum- appealing to force rather
than reason.
 Begging the Question- asserting a claim
in an argument intended to support it.
 Straw man (straw person)- attacking a
weak or absurd version of an argument,
and then pretending to have refuted the
strong version.
 Many others!

Evaluating Philosophical Arguments:

Fair-Mindedness and the State of
Suspended Judgment: When evaluating
arguments, we should strive to be
impartial and fair-minded. We should try
to follow where the best reasons lead
instead of pre-judging the conclusion.
Next: Deductive Arguments

Deductive Argument: An argument that
has the property that if the premises are
true, then the conclusion cannot be false.

Example:



All vertibrates have hip bones.
Snakes are vertibrates.
Therefore, snakes have hipbones.
Deductively Valid Arguments:

Df: An argument is (df) deductively valid iff it
has the property that if the premises are true,
then the conclusion cannot be false.
Example: (From Aristotle’s Logic)
1) All men are mortal.
2) Socrates is a man.
3) Therefore, Socrates is mortal.
Comments:

Deductive validity is a property of the form of an argument. The
following arguments have the same form
All fish are cold blooded.
Whales are fish.
Therefore whales are cold-blooded.
All goats are quadrupeds.
Abedna is a goat.
Abedna is a quadruped.
All philosophers are geniuses.
Clark is a philosopher.
Clark is a genius.

These arguments exemplify a valid form, so they are all valid. But
note that some of these arguments contain false statements. How
can an argument be valid if it has false premises?
Comments about Validity:
Consider the definition:







Df: An argument is (df) deductively valid iff it has the property
that if the premises are true, then the conclusion cannot be false.
A valid argument can have false premises.
A valid argument can have a false conclusion.
A valid argument can have false premises and a false
conclusion.
A valid argument can have false premises and a true
conclusion.
A valid argument cannot have true premises and a false
conclusion.

Examples…
Comments about Validity:
Two Examples of Valid (but faulty) Arguments:
False premises and false conclusion:
1) All horses are reptiles.
2) All reptiles have wings.
3) Therefore all horses have wings.
False Premises, True Conclusion:
1) All horses are reptiles.
2) All reptiles have fur.
3) All horses have fur.
These are both valid arguments. Since their premises are false, they do not
provide good evidence for their conclusions.
Soundness:
An argument is sound iff it is
deductively valid, and its
premises are true.
Some Valid Argument Forms:
Modus Ponens:
If X then Y.
X.
Therefore, Y.
Example:
1) If Jon swam in the Skunk river, then he’ll stink.
2) Jon swam in the skunk river.
3) Jon stinks.
Some Valid Argument Forms:
Modus Tollens:
If X then Y.
not Y.
Therefore, not X.
Example:
1) If Jon swam in the Skunk river, then he’ll stink.
2) Jon doesn’t stink.
3) Jon didn’t go swimming in the Skunk.
Some Related Invalid Forms:
Affirming the Consequent: If X then Y.
Y.
Therefore, X.
Example:
1) If Jon swam in the Skunk river, then he’ll stink.
2) Jon stinks.
3) Jon went swimming in the Skunk.
Some Related Invalid Forms:
Affirming the Consequent: If X then Y.
Y.
Therefore, X.
Counter-example:
1) If Jon throws water on the streets, then the streets will
be wet.
2) The streets are wet.
3) Jon must have thrown water on them.
Obviously this is a bad argument: If you find that the
streets are wet, it’s more likely that it’s rained than that
someone has been out dumping water around.
Some Related Invalid Forms:
Denying the Antecedent:
If X then Y.
Not X.
Therefore, not X.
Example:
1) If Jon swam in the Skunk river, then he’ll stink.
2) Jon didn’t swim in the Skunk.
3) Jon won’t stink.
(What if he’s been out shoveling manure?)
Quiz: Which are valid? What’s the Form?
1)
2)
3)
1)
2)
3)
If you ride your bike,
you’ll get strong.
You’re strong!
You must be a bike
rider.1
If you find a penny, you’ll
have luck all day.
You found a penny!
You’ll have a lucky day.
1)
2)
3)
1)
2)
3)
If he eats that fish, he’ll
die!
Ah! He didn’t eat the
fish.
He must still be alive.
If you had taken logic,
you would know how to
distinguish valid from
invalid arguments.
You can’t tell which are
valid and which are not!
You didn’t take logic.
Quiz: Which are valid? What’s the Form?
1)
2)
3)
If you ride your bike, you’ll get
strong.
You’re strong!
You must be a bike rider.
Invalid!
Form: Affirming the Consequent.
1)
2)
3)
If you find a penny, you’ll have luck
all day.
You found a penny!
You’ll have a lucky day.
1)
2)
3)
If he eats that fish, he’ll die!
Ah! He didn’t eat the fish.
He must still be alive.
Invalid.
Form: Denying the Antecedent.
1)
2)
3)
If you had taken logic, you would
know how to distinguish valid
from invalid arguments.
You can’t tell which are valid and
which are not!
You didn’t take logic.
Valid.
Form: Modus ponens.
Valid.
Modus Tollens.
Aristotelian Syllogisms: Some
other Valid Argument Forms






All X are Y.
All Y are Z.
Therefore, all X are Z.

No X are Y.
S is Y.
S is not X.





All X are Y.
S is an X.
S is a Y.
All X are Y.
S is not Y.
S is not X.
Aristotle’s Logic is a detailed and sophisticated analysis of simple
arguments like these. For almost 2000 years, this was the state of
the art!
An Informal Method for Testing Validity:
1) Distinguish the argument’s form from it’s substance.
2) Write out an abstract version of the argument’s form: Do
this by drawing a circle around each substantial
statement and replacing it with a letter.
3) Try to fill in the letters with alternative substance in such
a way that you make the premises true, and the
conclusion false. This is a counterexample to the
argument.
If you can find a counterexample of this kind, then you
know that the argument was invalid.
Testing validity with a counterexample:
“In order to institute a stable regime in Iraq and pull
out, we need help from our former allies. But if
Bush wins the election, then our former allies will
continue to refuse to help us. So if Bush wins the
election, we will not be able to institute a stable
regime and pull out of Iraq.”
“If moral relativism were true, then we should
expect to find that different cultures have very
different moral values. But this is just what we do
find: different cultures do have different moral
values. Therefore moral relativism must be true.”
Testing validity with a counterexample:
“In order to institute a stable regime in Iraq and pull out, we need help
from our former allies. But if Candidate Bush wins the election, then
our former allies will continue to refuse to help us. So if Bush wins the
election, we will not be able to institute a stable regime and pull out of
Iraq.”
Interpretation:
If we wish to pull out of Iraq, then we need help from our allies.
If Bush is elected we won’t have help.
If Bush is elected, then we won’t be able to pull out.
Form:
If X then Y
If B then Not Y.
If B then not X.
This argument is valid: No counterexample will be forthcoming. But
note that if you fail to find a counterexample, you don’t know for sure
that the argument is valid! Note also that my assurance that the
argument is valid does not prove that the conclusion is true: Perhaps
one of the premises is false.
Another interpretation:
“If (institute a stable regime in Iraq) and (pull out) then (we
need help from our former allies.)
If (Bush wins) then (our allies won’t help) Therefore if (Bush
wins) then (no stable regime) and (won’t pull out of Iraq).
If (X and Y) then Z.
If B then Not Z
If B then Not (X and Y)
(Still valid.)
One more thing to notice: Even though this argument is valid,
it implies nothing about whether we will be able to pull out of
Iraq and institute stability if Bush does not win. The
argument is consistent, for example, with the view that we
can’t accomplish these things no matter who wins the
election.
Testing validity with a counterexample:
“If moral relativism were true, then we
should expect to find that different cultures
have very different moral values. But this
is just what we do find: different cultures
do have different moral values. Therefore
moral relativism must be true.”
If X then Y.
Y.
Therefore X.
You already know that this argument is invalid,
Since it affirms the consequent. But for a
Counterexample:
Counterexample:
If an animal is a dog, then it must have hair.
My pet spider has hair.
Therefore my pet spider is a dog.(?)
Testing Validity:
If you were to take a class in formal logic,
you would learn more reliable and
technical ways to test for validity. When
arguments are very complicated, you can’t
always simply see that they are valid or
invalid.
Nondeductive Arguments
Can be Good Arguments:

Deductive arguments guarantee the truth of their
conclusions… given the truth of the premises.

Inductive and abductive arguments do not
guarantee the truth of the conclusion, but when
such arguments are strong, they provide good
evidence that the conclusion is true. If you have
a good non-deductive argument for a claim, then
you have reason to believe that it is probably
true.
Facts about Inductive Arguments:

Inductive arguments are never valid, but they may still
be good arguments. Inductive arguments are said to be
strong when they provide good evidence that the
conclusion is true, and weak when they don’t provide
good evidence.

Inductive arguments are Strong when the sample is
large and representative. They are weak when the
sample is small or unrepresentative.
Dick should not drink the coffee.
Inductive and Abductive Arguments

Inductive Argument (or ‘induction’): A
nondeductive argument in which characteristics
of individuals not in a sample are inferred from
the characteristics of individuals in a sample.

Abductive argument (or ‘abduction’): A form of
nondeductive inference, also called “inference to
the best explanation” in which a hypothesis is
supported on the ground that it is the best
explanation for some observed phenomenon.
Inductive and Abductive Arguments
Here is an example of an inductive argument:
(1) 95% of all examined fish from the Otsoga river
contained dangerous levels of mercury.
(2) This fish came from the Otsoga river.
(3) Therefore, this fish (probably) contains
dangerous levels of mercury.
Weak Inductive Arguments:
1) All Bob’s friends say that they plan to vote for
Mitt Romney.
2) Therefore, it seems likely that Romney will carry
Iowa by a landslide.
Problem: Unrepresentative Sample. ‘Bob’s
friends’ are not likely to be a representative
sample of Iowans as a whole. If Bob plans to
vote for Romney, then it’s likely that many of his
friends are like-minded voters.
Weak Inductive Arguments:
1) On interviewing six students at the Union, it was
found that four of them planned to spend the
summer in Iowa, while two of them planned to
go abroad.
2) Therefore, 33% of ISU students (probably) plan
go abroad during the summer.
Problem: Sample size too small. Six students
is too small a number to make predictions about
the whole student body.
Abductive Arguments:
“The world must be spherical in shape. For the night sky
looks different in the northern and southern regions, and this
would be so if the earth were spherical.” -Aristotle, Physics.
To put this argument in standard form, we might interpret it as
follows:
(1) The night sky looks different in the northern and southern
regions.
(2) The best explanation for this fact is that the earth is round.
(3) Therefore (probably) the earth is spherical in shape.
Evaluating Abductive Arguments:

Abductive arguments are stronger if the
explanation posited in the conclusion is the only
explanation that will adequately account for the
phenomenon to be explained, or if it is the most
likely of a small set of possible explanations.

Abductive arguments are weaker if there are
many other plausible explanations that would
account for the phenomenon, or if we have
independent reason to believe that the
explanation offered is unlikely.
Evaluating Abductive Arguments:
1)
2)
3)
There is an odd and very loud banging
sound coming from the classroom
upstairs from our own.
If there were elephants up there, it would
explain the sounds we hear.
There are elephants in the room upstairs
from our classroom.
Evaluating Abductive Arguments:
Why is the argument weak?
1) There are many alternative explanations
for the sounds we hear.
2) We have independent reason to doubt
that there are elephants upstairs.
Evaluating Abductive Arguments:
When is an abuductive argument weak?
1) When the explanation offered is only one of
many alternative explanations for the sounds
we hear.
2) When alternative explanations are simpler,
independently more plausible, or otherwise
preferable to the explanation offered.
3) Where there is independent reason to doubt
the offered explanation.
An Argument for Analysis
“People may seem to be kind, compassionate,
or altruistic, but if you really search out the basis
of their actions you will discover that they’re
really behaving selfishly. Every voluntary action
is motivated by the values of the actor herself.
So in all of our voluntary actions, we are
pursuing our own ends. Exclusively to pursue
one’s own ends is to be selfish. So all of our
voluntary actions are ultimately selfish.”
“People may seem to be kind, compassionate, or altruistic, but if you really search
out the basis of their actions you will discover that they’re really behaving selfishly.
Every voluntary action is motivated by the values of the actor herself. So in all of our
voluntary actions, we are pursuing our own ends. Exclusively to pursue one’s own
ends is to be selfish. So all of our voluntary actions are ultimately selfish.”
1) Every voluntary action is motivated by the values of the actor herself.
2) So in all of our voluntary actions, we are pursuing our own ends.
3) Exclusively to pursue one’s own ends is to be selfish.
Conclusion: All voluntary actions are selfish.
Some Theories of Human Action:
Psychological Egoism: All voluntary human actions are ultimately selfish.
Ethical Egoism: Actions are morally right if and only if they are selfish.
Evaluating Philosophical Arguments

(1) First Pass: First, read through the
work rather quickly, noting difficult words,
concepts and claims as you go. Make
certain that you understand the main
points the author is trying to make, and be
sure to look up any unfamiliar or confusing
terms or concepts.
Evaluating Philosophical Arguments

(2) Read for Understanding: In your
second pass through the material, you
should read slowly and deliberately. Take
notes. Make sure that you understand
each of the arguments offered, and that
you understand what reasons are given to
support the conclusions the author hopes
to support. Clarify the claims the author
makes—make sure you understand what
the author means.
Evaluating Philosophical Arguments

(3) Criticism and Objections: After you
have finished reading the material
carefully and have an understanding of the
author’s arguments, evaluate the claims
made and the evidence given. Articulate
the strongest objections and counterarguments you can develop: try to
construct an argument against the position
the author has defended.
Evaluating Philosophical Arguments

4) Re-Evaluation of the Argument:
Finally, go back and read the text again,
keeping in mind the objections you have
raised and the counter-arguments you
have developed. Does the author have
resources to respond to your objections
and counter-arguments? Are your
objections conclusive, or are you inclined
to accept the conclusion as well supported
by the argument?
Example: Anselm







O Lord, you who give understanding to faith, so far as you know it to be beneficial, give me to
understand that you are just as we believe , and that you are what we believe.
We certainly believe that you are something than which nothing greater can be conceived.
But is there any such nature, since “the fool hath said in his heart: “God is not.”
However, when this very same fool hears what I say, when he hears of “something than
which nothing greater can be conceived,” he certainly understands what he hears.
What he understands stands in relation to his understanding (esse in intellectu), even if
he does not understand that it exists. For it is one thing for a thing to stand in relation to our
understanding; it is another thing for us to understand that it really exists. For instance, when a
painter imagines what he is about to paint, he has it in relation to his understanding. However,
he does not yet understand that it exists, because he has not made it. After he paints it, then
he both has it in relation to his understanding and understands that it exists. Therefore, even if
the fool is convinced that “something than which nothing greater can be conceived” at least
stands in relation to his understanding, because when he hears of it he understands it, and
whatever he understands stands in relation to his understanding.
And certainly that than which a greater cannot be conceived cannot stand only in
relation to the understanding. For if it stands at least in relation to the understanding, it can be
conceived to be also in reality, and this is something greater. Therefore, if “that than which a
greater cannot be conceived” only stood in relation to the understanding, then “that than which
a greater cannot be conceived” would be something than which a greater can be
conceived. But this is certainly impossible.
Therefore, something than which a greater cannot be conceived undoubtedly both
stands in relation to the understanding and exists in reality. (Saint Anselm, from Sober, p. 125)
ON TO PLATO!