Transcript Philosophy in Practice - University of Warwick

Philosophy in Practice
Lecture 3: Introduction to
Critical Reasoning
Outline of the lecture
• Recap: last lecture
• Identifying premises and conclusions
• Implicit/explicit premises and
conclusions
• Fallacies to look out for
• Module assessments
Antecedent and consequent
A conditional statement is one that is structured
like this: “if…then…”. So a conditional
statement is composed of two parts:
• The first part is called the antecedent (and
follows ‘if’)
• The second part is called the consequent (and
follows ‘then’)
If antecedent, then consequent
Necessary and sufficient
• The antecedent is supposed to be sufficient
(enough) for the consequent.
• The consequent is supposed to be necessary
(required) for the antecedent.
If you were born in London, then you were born
in England.
• Being born in London is sufficient but not
necessary for being born in England.
• Being born in England is necessary but not
sufficient for being born in London.
Affirming the antecedent
P1: If the mind and body are distinct then we may
survive our bodily deaths.
P2: The mind and body are distinct.
_________________________
C: We may survive our bodily deaths.
If P, then Q
P
Therefore Q
Valid argument, also known as ‘modus ponens’.
Denying the consequent
P1: If backwards time travel were possible, then
people would have come back from the future to visit
us.
P2: People haven’t come back from the future to visit
us.
_________________________
C: Backwards time travel is not possible.
If P, then Q
Not-Q
Therefore, not-P
Valid argument, also known as ‘modus tollens’
Disjunctive syllogism
P1: Either the giant duck is the biggest bird or the
giant sparrow is the biggest bird.
P2: The giant sparrow is not the biggest bird.
--------------------------------------------------------------------C: The giant duck is the biggest bird.
Either P or Q
Not-Q
Therefore, P
Valid argument
Affirming the consequent
P1: If the suspect is lying, he will start sweating
P2: The suspect is sweating.
_________________________
C: The suspect is lying.
If P, then Q
Q
Therefore, P
Invalid argument
Denying the antecedent
P1. If it's raining, then the streets are wet.
P2. It isn't raining.
_________________________
C. The streets aren't wet.
If P then Q
Not-P
Therefore, not-Q
Invalid argument
Conditionals vs. arguments
Note the key difference between
conditionals and arguments.
• Conditionals can be true or false
• Arguments can be valid or invalid
Identifying arguments
In our increasingly atheist society, most people
now implicitly endorse materialism about the
most profound of metaphysical questions. One
primary example of this is the question of the
relationship between the mind and the brain.
Many just take it for granted that all mental
phenomena can be explained in terms of
physical processes in the brain. People really
need to snap out of this science delusion.
Q: is this an argument? If so, what is the
conclusion and what are the premises?
Identifying arguments
(1) In our increasingly atheist society, most people
now implicitly endorse materialism about the
most profound of metaphysical questions. (2)
One primary example of this is the question of
the relationship between the mind and the
brain. (3) Many just take it for granted that all
mental phenomena can be explained in terms
of physical processes in the brain. (4) People
really need to snap out of this science delusion.
No argument. (1)-(3) are scene-setting.
(4) is an unsupported assertion.
Identifying arguments
There is a trend today that supports regulating
British industry in the name of the environment.
For example, ‘green’ organisations advocate the
placing of limitations on the amount of carbon our
industries can expel into the atmosphere. It is my
view that we must not give in to this demand. The
principal reason for this is that curbing carbon
emissions simply will not solve the problem that it
is supposed to address: the problem of global
warming. We shouldn’t adopt policies that don’t
solve the problems they are supposed to address.
Q: is this an argument? If so, what is the
conclusion and what are the premises?
“(1) There is a trend today that supports regulating
British industry in the name of the environment. (2)
For example, ‘green’ organisations advocate the
placing of limitations on the amount of carbon our
industries can expel into the atmosphere. (3) It is my
view that we must not give in to this demand. (4) The
principal reason for this is that curbing carbon
emissions simply will not solve the problem that it is
supposed to address: the problem of global warming.
(5) We shouldn’t adopt policies that don’t solve the
problems they are supposed to address.”
Conclusion: Sentence (3): We should not limit carbon
emissions.
Premises: Sentences (4) and (5)
• Limiting carbon emissions will not solve the problem
that it is supposed to address (global warming).
• We should not adopt policies that don’t solve the
problems they are supposed to address
Extraneous Material: Sentences (1) & (2): scenesetting & rhetoric
Reconstructing arguments
P1: Limiting carbon emissions will not solve the
problem that it is supposed to address (global
warming).
P2: We should not adopt policies that don’t solve
the problems they are supposed to address.
______________________________
C: We should not limit carbon emissions.
Implicit/explicit
You should avoid Danny. He has some very
dubious ideas. For proof of this, look no
further than the fact that he’s a member of
the BNP!
Q: is this an argument? If so, what is the
conclusion and what are the premises?
Implicit/explicit
You should avoid Danny. He has some very dubious
ideas. For proof of this, look no further than the fact
that he’s a member of the BNP!
Conclusion: You should avoid Danny. (explicit)
Explicit Premises:
• Danny is a member of the BNP.
• Danny has some very dubious ideas.
Implicit Premises:
• (1) If you are a member of the BNP then you have
some very dubious ideas. (2) If someone has very
dubious ideas then you should avoid them.
Reconstructing arguments
You should avoid Danny. He has some very
dubious ideas. For proof of this, look no further
than the fact that he’s a member of the BNP!
P1: If you are a member of the BNP then you
have very dubious ideas.
P2: Danny is a member of the BNP.
___________________________________
C1: Danny has very dubious ideas.
Reconstructing arguments
You should avoid Danny. He has some very dubious
ideas. For proof of this, look no further than the fact
that he’s a member of the BNP!
P1: If you are a member of the BNP then you have
very dubious ideas.
P2: Danny is a member of the BNP.
____________________
C1: Danny has very dubious ideas.
P3: If someone has very dubious ideas then you
should avoid them.
____________________
C2: You should avoid Danny.
Implicit/explicit
In our disenchanted society it has become
fashionable to say that morality is all just a matter of
opinion. But if morality was subjective then people
wouldn’t think that it is possible to be mistaken about
moral matters. With this in mind consider the
following: we think that previous generations were in
error when they believed that slavery wasn’t wrong.
Also, we think that psychopaths who say there is
nothing wrong with killing innocent people are saying
something which is obviously false. I really think
people should reflect more about these things.
Q: is this an argument? If so, what is the conclusion
and what are the premises?
Implicit/explicit
(1) In our disenchanted society it has become fashionable to
say that morality is all just a matter of opinion. (2) But if
morality was subjective then people wouldn’t think that it is
possible to be mistaken about moral matters. (3) With this in
mind consider the following: we think that previous
generations were in error when they believed that slavery
wasn’t wrong. (4) Also, we think that psychopaths who say
there is nothing wrong with killing innocent people are
saying something which is obviously false. (5) I really think
people should reflect more about these things.
Conclusion: Morality is not subjective (implicit).
Premises:
Explicit (sentence (2)): If morality was subjective then
people would not think that it is possible to be mistaken
about moral matters.
Implicit ((3) and (4)): People do think that it is possible to be
mistaken about moral matters.
Extraneous material: (1): scene setting; (5): irrelevant
observation.
Reconstructing arguments
P1: If morality was subjective then people would
not think that it is possible to be mistaken about
moral matters.
P2: People do think that it is possible to be
mistaken about moral matters.
__________________________________
C: Morality is not subjective.
Implicit/explicit
They recycle obsessively, insist on real nappies and
compost every scrap of organic vegetable peeling
and used Fair Trade teabags – and they’re not slow to
tell you about it. But when it comes to sacrificing
their jaunts to Tuscany and weekend breaks in
Prague, it seems that even the most pious of green
crusaders waver in their zeal for saving the planet.
Coldplay frontman Chris Martin - who uses his lyrics
to urge environmental responsibility - flies home
between gigs, while George Clooney – who drives a
low-emissions Tango car – also uses private jets. It
goes without saying what the public’s attitude ought
to be towards the advice of both of these ecohypocrites.
Q: is this an argument? If so, what is the conclusion
and what are the premises?
(1) They recycle obsessively, insist on real nappies and compost
every scrap of organic vegetable peeling and used Fair Trade
teabags – and they’re not slow to tell you about it. (2) But when it
comes to sacrificing their jaunts to Tuscany and weekend breaks
in Prague, it seems that even the most pious of green crusaders
waver in their zeal for saving the planet. (3) Coldplay frontman
Chris Martin - who uses his lyrics to urge environmental
responsibility - flies home between gigs, while George Clooney –
who drives a low-emissions Tango car – also uses private jets. (4)
It goes without saying what the public’s attitude ought to be
towards the advice of both of these hypocrites.
Conclusion: Implicit in sentence (4): We should ignore the advice
of Chris Martin and George Clooney about living in an
environmentally friendly way.
Premises:
• Implicit in sentences (2) (3): The behaviour of Chris Martin and
George Clooney is inconsistent with their advice about living in
an environmentally friendly way.
• Implicit: Whenever someone’s behaviour is inconsistent with
their advice, we should ignore the advice
Extraneous Material: Sentence (1) – scene-setting, rhetoric.
Sentence (2) – scene-setting, more rhetoric.
Reconstructing arguments
P1: The behaviour of Chris Martin and
George Clooney is inconsistent with their
advice about living in an environmentally
friendly way.
P2: Whenever someone’s behaviour is
inconsistent with their advice, we should
ignore the advice.
______________________________
C: We should ignore the advice of Chris
Martin and George Clooney about living in an
environmentally friendly way.
Keep in mind…
• Premises are either true or false. Therefore,
questions and commands cannot figure as
premises or conclusions.
When reconstructing arguments:
• The sentences we use need not be the same
as the sentences used by the arguer
• We’re trying to express what the arguer is
saying more clearly (but without, of course,
changing what they’re saying)
• In addition, our reconstruction may contain
premises that are not expressed by any of the
sentences actually used by the arguer
Keep in mind…
This is not an exact science:
“It cannot be mechanical or foolproof. It calls for
judgment, a critical but sympathetic eye or ear
and even a degree of intuition, of understanding
of people – of the ways people tend to think in
given sets of circumstances, and some of the
typical ways in which people fail to express
themselves clearly.”
(Bowell and Kemp, 2nd Edition: Ch.2 p. 45; 3rd
Edition: Ch.3, p. 57)
Keep in mind…
The principle of charity
If we are interested in whether the
conclusion is true or not, or whether we
have in fact been given good reasons for
thinking it to be true, then we should aim to
reconstruct the argument in its strongest
form.
Deriving ‘ought’ from ‘is’
This is the fallacy of deriving a prescriptive
conclusion (i.e., a conclusion about what ought to
be done, or what should be done, or what is good,
bad, wrong, right) from non-prescriptive
premises.
P1: Capitalism inevitably leads to financial crises.
______________________________
C: We should overthrow capitalism.
In order to be valid, we need a prescriptive
premise linking X’s leading to financial crises and
it being the case that X should be overthrown.
Fallacy of majority belief
Majority Belief: This is the fallacy of concluding on
the basis of the fact that most people believe some
proposition, p, that p is true.
Although there is a tiny minority of people who
disagree with our health care reforms, the
overwhelming majority of British citizens know that
they will make the NHS better. In light of this
overwhelming consensus it is clear that this
Government’s health policy is going to greatly
improve our National Health Service.
P1: The majority of people believe that the that the
reforms will make the NHS better.
P2: Any belief held by the majority is true. (false)
________________________________
C: The health care reforms will make the NHS better.
The report (submit week 10)
• Write the report as though
it’s going to be presented
to the public (i.e. it’s not a
formal essay). The report
has to be accessible to
someone who hasn’t
studied any philosophy.
Think about the best way
to communicate the
arguments.
• You may want to approach
this by taking both sides
of the argument, or
breaking down the
dominant argument.
• Feel free to use bullet
points if that makes
things better.
• Choose a topic that interests you.
Some suggestions:
• Abortion
• Euthanasia
• Animal rights
• Affirmative action
• Capital punishment
• Racial profiling
• Same-sex marriage
• Pornography
• Decriminalisation of drugs
• Immigration
• Humanitarian intervention
• World hunger
Presentation
• Lecture next week on presentations
• Workshops in week 7 (sign up on Tabula)
• Optional workshop in week 8 (max. 20
places)
• You will submit your presentation (handout, PowerPoint, Prezi etc. as part of your
assessment)
• Presentations in front of seminar groups
(weeks 9 and 10)
• Not a charisma contest
Précis
• Submit word précis in week 5
• 450-500 words (no more or less)
• The précis is a concise summary of your
report (an overview of the argument)
• What are the questions you’ll look at?
• What are the problems that define the issue?
• What is your angle going to be?
• It’s difficult to summarise the argument before
you’ve done extensive research, so you will
have to do some of the research over the next
fortnight.
Bibliography
Bibliography
Argyle, Fiona. 2002. Footwear and Cultural Subversion
(Cambridge, MA: Hardware University Press).
Bunion, Dan. 1978. ‘Polyester Blends and Thin Concepts’,
Podological Review, (89), pp.115-39.
Calcetin, Alicia (ed.). 1981. Socks on Feet, Socks on Trial, 3
vols (Laramie, WY: University of Heel Press).
Hose, Ivan, and Louise Chaussette. 2006. ‘Let the Socks Fall
Where They May’, in Culture Online http://www.cultonline.co.uk
[accessed 29 April 2007].
Nehigh, Anders. 2004a. Socks and Necessity (Oxford:
Harendon Press).
______ 2004b. ‘Socks and the Separation of Shoes and Feet: A
Critical Survey’, in Brownwell Companion to Philosophy and the
Lower Limbs, ed. Carol Leggett (London: Brownwell), pp.3-37.
Sandal, Greta. 1957. Wool, Elastic, and the Wearable, trans.
Kurt Tonhale (New York: Harper & Towe).
Bibliography
Plato – The Symposium – translated by
Christopher Gill for Penguin Classics, 1999
• Frisbee C.C. Sheffield – 2006. The Role of the
Earlier Speeches in the Symposium: Plato's
Endoxic Method? - Harvard University Press
Ludwig Edelstein - The Rôle of Eryximachus in
Plato's Symposium, Transactions and
Proceedings of the American Philological
Association, Vol. 76 – American Philological
Association, 1945 http://www.jstor.org/stable/283327