Transcript Critical Thinking - The Open University

Critical Thinking
Tim Lewis
18/03/2015
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Hypothesis
• An hypothesis is a specific statement of prediction. It
describes in concrete (rather than theoretical) terms
what you expect will happen in your study. Not all
studies have hypotheses. Sometimes a study is
designed to be exploratory. There is no formal
hypothesis, and perhaps the purpose of the study is to
explore some area more thoroughly in order to
develop some specific hypothesis or prediction that
can be tested in future research. A single study may
have one or many hypotheses.
• http://www.socialresearchmethods.net/kb/hypothes.p
hp
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Hypothesis (OED)
• A proposition or principle put forth or stated
merely as the basis for reasoning or argument,
or as a premise from which to draw a
conclusion.
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Thesis (OED)
• A proposition laid down or stated, esp. as a
theme to be discussed and proved, or to be
maintained against attack.
• A dissertation to maintain and prove a thesis;
especially one written or delivered by a
candidate for a university degree 1653.
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The Nature of Argument
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Argument
• an argument is an attempt to persuade
someone of something, by giving reasons for
accepting a particular conclusion as
evident. The general structure of an argument
… is that of premises (typically in the form
of propositions, statements or sentences) in
support of a claim: the conclusion
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Syllogisms
(Major) Premise : All men are mortal
(Minor) Premise : Socrates is a man
Conclusion: Therefore Socrates is mortal
(Major) Premise : All kittens are playful
(Minor) Premise: Some pets are kittens
(Conclusion): Some pets are playful.
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Syllogism -definition
• A syllogism is a kind of logical argument in which
one proposition is inferred from two or more
others (the premises) of a specific form. A
syllogism has three parts: major premise, minor
premise, and conclusion. The major premise of a
syllogism makes a general statement that the
writer believes to be true. The minor premise
presents a specific example of the belief that is
stated in the major premise. If the reasoning is
sound, the conclusion should follow from the two
premises.
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False Syllogisms
• All dogs can fly.
• Fido is a dog.
• Fido can fly.
• Slavery is work.
• Slavery is evil.
• Therefore all work is evil.
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Deductive Argument
• Deductive reasoning is the process
of reasoning from one or more general
statements (premises) to reach a logically
certain conclusion.
• Premises are linked with conclusions by a
process of inference. If all premises are true,
the terms are clear, and the rules of
deductive logic are followed, then the
conclusion reached is necessarily true.
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Inductive Argument
• Inductive reasoning is reasoning in which the
premises seek to supply strong evidence for (not
absolute proof of) the truth of the conclusion.
While the conclusion of a deductive argument is
supposed to be certain, the truth of an inductive
argument is supposed to be probable, based
upon the evidence given.
• Inductive reasoning forms the basis of
most scientific theories e.g.; Darwinism, Big Bang
Theory and Einstein’s Theory of Relativity.
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Arguments: logic and rhetoric
• The standards and criteria used in
evaluating arguments and their
forms of reasoning are studied in
logic. Ways of formulating arguments
effectively are studied in rhetoric
(also known as argumentation
theory).
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Deduction and Induction
Handout
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Fallacies (1)
• Guilt by Association: “Hitler was a vegetarian,
therefore, I don’t trust vegetarians.”
• Ad Hominem: “Don’t listen to Eddie’s
arguments on education, he’s an idiot.”
• Appeal to Authority: “Well, Isaac Newton
believed in Alchemy, do you think you know
more than Isaac Newton?”
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Fallacies (2)
• Argument from Ignorance: “No one has been able
to disprove the existence of UFOs, therefore they
exist.”
• Non sequitur: “I read about a pitbull attack. My
neighbour owns a pitbull. My life is in danger.”
• Slippery slope: “If voluntary euthanasia is
legalised it will be impossible to avoid the
legalisation, or, at least, toleration, of nonvoluntary euthanasia.”
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Activities
• 1. The Sun says: Arrogant Left
Reconstitute the argument of this Sun
editorial in the form of a syllogism (a
deductive argument).
• 2. Sex Vote Labour Chiefs/Scientists’ Hidden
Links to the GM Food Giants
What kind of arguments are being used in
these two handouts?
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Sun Leader as syllogism
P1
Senior members of the Labour Party
tolerated paedophiles in the 1970s.
P2
Their refusal to apologize for this has been
supported by Ed Miliband as party leader.
C
He and they are guilty of arrogant
defiance.
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SOUND ARGUMENTS
• DEDUCTIVE
• INDUCTIVE
arguments are
arguments are
SOUND when the
SOUND when the
premises are TRUE
supporting
and the LOGIC is
EVIDENCE for
VALID.
them is judged to
be ACCEPTABLE
and RELEVANT.
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Using Evidence
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Evidence
• Evidence, broadly construed, is anything
presented in support of an assertion. This
support may be strong or weak. The strongest
type of evidence is that which provides
direct proof of the truth of an assertion. At
the other extreme is evidence that is merely
consistent with an assertion but does not rule
out other, contradictory assertions, as
in circumstantial evidence.
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Scientific Evidence
• Scientific evidence consists
of observations
and experimental results that serve to
support, refute, or modify a scientific
hypothesis or theory, when collected
and interpreted in accordance with
the scientific method.
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Handouts
• Home Secretary speech on `An immigration
system that works in the national interest’
• Article by Jonathan Portes (National Institute
of Economic and Social Research) `Theresa
May’s immigration speech: facts or fiction’
• Article by Andrew Grice (Political Editor, The
Independent) `May’s stance on immigration
and jobs “not proven”’
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Using Evidence 1
1. Read pp. 1-4 of Theresa May’s speech: `An
Immigration system that works in the
national interest’.
2. List all the sources of evidence identified by
Theresa May. (pp. 1 & 4)
3. List the three areas in which May claims
immigration has a negative impact. (pp.2-3)
4. Identify any conclusions for which May says
that there is `evidence’. (pp. 3-4)
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Sources of evidence identified by Theresa
May:
•
•
•
•
•
•
•
•
•
yesterday’s census statistics (p.1)
official statistics released two weeks ago (p.1)
Home Office visa statistics (p.1)
which are more up to date than
net migration figures (p.1)
the Migration Advisory Committee report (p.4)
which is based on
several academic studies (p. 4)
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The three areas in which May claims
immigration has a negative impact
• social cohesion (p. 2)
• infrastructure (especially housing)
and public services (p.3)
• employment (jobs and wages) (p.3)
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Conclusions for which May says that
there is `evidence’
• ` There is evidence that without the demand
caused by mass immigration, house prices
could be ten per cent lower over a twenty
year period’ (p.3)
• `There is evidence … that immigration puts
downward pressure on wages’ (p.4)
• `That is evidence of an immigration system
that does not work in the national interest’
(p.4)
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Using Evidence 2
• Read Jonathan Portes’ Article `Theresa May’s
immigration speech: facts or fiction?’
• List up to five main criticisms Jonathan Portes
makes of Theresa May’s use of evidence
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Five criticisms of Theresa May’s use of
evidence
1. May’s use of statistical evidence is HIGHLY
SELECTIVE (p.2). She OMITS inconvenient points
and restrictions (p.4).
2. May EXAGGERATES, or goes `well beyond what
the MAC said or what the research actually
found’. (p.2)
3. May argues by IMPLICATION and (p.3)
4. Some of May’s arguments ARE NOT BORNE OUT
by, or are CONTRARY to the evidence. (p.3)
5. May’s IDENTIFICATION OF the SOURCES for
some of her claims is UNCLEAR. (p.4)
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How to deal with evidence
1. Present ALL the evidence you have, or at least a
REPRESENTATIVE SAMPLE of it.
2. DO NOT EXAGGERATE the claims you make,
beyond what the evidence will bear.
3. Make your arguments OVERT and EXPLICIT.
4. Check that your ARGUMENTS are IN LINE WITH
the EVIDENCE
5. Always IDENTIFY YOUR SOURCES CLEARLY and as
SPECIFICALLY as possible (to enable verification).
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Critical Reading
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Handout and Activity
1. Read Wallace and Wray, Chapter 3 `Getting
Started on Critical Reading’ (pp. 28-35) and
2. Answer the questions on the worksheet
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References
• http://www.socialresearchmethods.net/kb/
• http://plato.stanford.edu/entries/logicinformal/
• Mike Wallace and Alison Wray, Critical
Reading and Writing for Postgraduates, 2nd
edition (London: Sage, 2011)
• Christopher W. Tindale, Rhetorical
Argumentation: Principles of Theory and
Practice (Sage: Thousand Oaks Ca, 2004)
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