Logic and Critical Thinking
CCC80001-4
2nd Term 2014
Course Instructor
Office: HSH (Ho Sin Hang) 213
Office Hours
Tuesday 4:00-6:00PM
& by appointment
My Email
michael.dracula.johnson@
gmail.com
Course Website
michaeljohnsonphilosophy.com
Course Meeting Times
Wednesday 2:30-4:00PM LKKG05
Friday 5:00-6:30PM LKK205
ASSESSMENT
Reading
There is no required reading in this class.
There is lots of optional reading on the course
website. I may give bonus marks to students
who can answer questions in class about the
optional reading!
Assessment
Attendance: 10%.
Four homework assignments, each worth 5% of
the grade, for a total of 20%.
One in-class midterm in March, worth 30%.
One cumulative final exam, worth 40%.
Short Homework Assignments
Homework assignments will ask you to apply
what we’ve learned in class to your own life and
experiences.
Example…
Out of Context: 1998-present
Broader Context: 1850-present
HW1
Find an example, from your own life and
experiences, where a piece of information was
taken out of context in a misleading way.
Student Example
Source: Erickson Times
Misleading Graphs
Source: Erickson Times
Rubric
• Describe the information taken out of context:
1 mark
• Describe the claim the information was used
to support, and who was making the claim:
2 marks
• Describe the broader context and why the
information presented was misleading:
2 marks
• Students’ own experience: 1 mark
Late Assignments
I won’t accept late homework. Even 1 minute
late is late. Sorry.
Attendance
Attendance is required and accounts for 10% of
your final grade.
You cannot get an ‘A’ in this course if you do not
attend classes.
Every day you don’t attend, you lose 0.5 marks
off your final grade, up to a maximum of 10.
Late to Class
You will not be counted as present if you show
up after I have called attendance. Please be in
class on time.
Final Exam
The final exam will happen during the scheduled
exam period. Exact time/ date TBA.
It will consist of multiple choice and short
answer questions.
It is worth 40% of the total marks.
Norm-Based Assessment
ACADEMIC INTEGRITY
IMPORTANT NOTE
Students shall be aware of the University
regulations about dishonest practice in course
work and the possible consequences as
stipulated in the Regulations Governing
University Examinations.
5.2a Collusion
A student misrepresents a piece of unauthorised
group work as his/her own work.
5.2b Falsification of Data
The presentation of data in reports, projects or
research papers, which is purported to be based
on experimental or research work conducted by
the student, has actually been invented by the
student, copied or obtained by unfair means.
5.2c Plagiarism
The presentation of another person's work
without proper acknowledgement of the source,
whether protected by copyright or not, as the
student's own work.
5.2d Anything Else Dishonest
For example, submission of same or
substantially same work for two assignments
without prior approval.
Policy on Cheating
I have zero tolerance for cheating.
When in doubt, ask me!
Policy on Talking in Class
(When You’re Not Contributing)
Zero tolerance.
WHAT IS CRITICAL THINKING?
“Critical thinking is the intellectually disciplined
process of actively and skillfully conceptualizing,
applying, analyzing, synthesizing, and/or
evaluating information gathered from, or
generated by, observation, experience,
reflection, reasoning, or communication, as a
guide to belief and action.” criticalthinking.org
What is Critical Thinking?
There are two basic decisions to make in life:
1. Decide what to believe: What do I believe?
2. Decide what to do: What do I do?
Deciding What to Believe
The things you believe (or disbelieve) are claims.
Examples of claims include:
• Aliens exist.
• 2 + 2 = 4.
• Pocari Sweat is better than Aquarius.
• You should kill children for fun.
Claims
Claims can be:
•
•
•
•
•
•
General or specific
Clear or ambiguous
True or false
Plausible or implausible
Reasonable or unreasonable
Supported by evidence or not…
Example: Theories
Scientific theories are
claims that are supported
by lots of evidence, that
integrate lots of our
knowledge, and that
explain and predict lots of
phenomena.
Example: Guesses
Guesses are claims that
the guesser only believes
might be true, or are
probably true.
Example: Lies
A lie is a claim that is
known to be false and is
made to deceive you into
believing something false.
Claims
There are lots of other types of claims:
hypotheses, deductions, considerations…
A claim is something that is presented as true.
Critical Thinking
Is there any evidence to support the claim?
Is the evidence reliable and trustworthy? How
reliable is it? Should you accept it?
Does the evidence actually support the claim?
Is there other evidence you should consider?
Critical Thinking
Critical thinking involves asking these questions
at the right times, knowing how to answer
them, and knowing how to use those answers to
accept or reject a claim.
This is a skills-oriented class. These are the skills
we will learn.
You Already Do It
You are already a critical thinker. You use critical
thinking skills all the time, even if you don’t
know it.
Critical Thinking and Skepticism
“Skepticism [critical
thinking]… is essentially a
form of basic intellectual
hygiene, something that
everyone is capable of to
varying degrees and
something that everyone
should do.”
-- Chris Clarke
Critical Thinking as Mental Hygiene
“Skepticism is to the intellect as brushing is to
teeth. Sometimes we need expert assistance,
but the only way it really does us any long term
good is if we engage in the practice of mental
hygiene as a habit, preferably after each bout of
consuming something that might cause
problems down the road, whether it’s a bag of
chips or an article in the New York Toast.”
Difference
“There is one thing where skepticism differs
from toothbrushing.
There aren’t legions of non-toothbrushers who
pour support and money towards cranks that
tell them to keep their mouths dirty.” – vaiyt
(Comment #20)
Is there any evidence?
Claim: Keeping your devices on poses a danger.
But is there any evidence that this is true? Are
there studies? What do scientists say?
Is there any evidence?
Flu season comes and it’s
really bad. You should
probably get a flu shot.
Or should you go to the
traditional Chinese
medicine shop? They say
their medicine can
prevent the flu too.
How reliable is the evidence?
Claim: Oh, you have a cold? You should get the
doctor to prescribe antibiotics for you.
Evidence: I got a cold and after a couple days
was feeling really bad. I got some antibiotics and
two days later, I felt great!
How reliable is the evidence?
But this can’t be true. Colds are caused by
viruses, and antibiotics only work on bacteria.
The story you heard is a case of regression to
the mean.
Colds usually take care of themselves in 6 days.
Does the evidence support the claim?
Companies often pay celebrities and other
public figures to endorse their products.
Claim: You should buy/ use this product.
Evidence: Celebrity X buys/ uses this product.
But is it any reason to buy something that some
other person is paid to say they like it?
Taishan Landmark in Guangdong
From SCMP
“A group of Hong Kong investors have called for
laws to regulate celebrity advertising, claiming
to have been misled into pouring money into a
Guangdong shopping arcade project…
They said they had been attracted to invest in
the project because of endorsements by local
celebrities, including a food critic and a fung
shui master.”
Crop Circles
Crop Circles
Crop circles remain one of the mysteries of the
ages.
What causes them?
What do they mean?
Are they all part of an elaborate conspiracy and
hoax?
-- WorldNetDaily
Is there other evidence to consider?
Claim: Prayer heals the sick.
Evidence: My mother had cancer, but then I
prayed for her. Her cancer went into remission.
But how many people were prayed for and not
cured? How many people were not prayed for,
but still had their cancer go into remission? Does
prayer work or was this just an accident?
Critical Thinking
Becoming a better critical thinker involves
exercising these skills, asking these questions
and finding out the answers, more often and
more effectively and in a wider range of
circumstances.
LOGIC
Logic
This course is called Logic and Critical Thinking,
and we will be learning about logic.
Logic is a helpful tool for verifying the quality of
arguments.
Philosophical Arguments
In ordinary English, an argument is where two or
more people have different views, and they
heatedly or angrily discuss them.
In philosophy, it’s when we present certain
claims as evidence for other claims. So critical
thinking is about evaluating arguments– are the
claims presented as evidence true? Do they
support the conclusions?
Validity
An important concept in logic is validity, a
particularly strong sort of evidential support.
An argument is valid = if the claims presented as
evidence in the argument (the “premises”) are
true, then the claim that evidence supports (the
“conclusion”) of the argument must be true
(cannot be false).
Formally Valid Arguments
Ancient philosophers (both Western and
Chinese) discovered that you can tell that some
arguments are valid by looking at their form
alone.
Example
Here’s an example of a valid argument form:
Evidence: If A is true, then B is true.
Evidence: A is true.
Claim: Therefore, B is true.
Notice that even if you don’t know what the
claims A and B are, you know that if the
evidence is true, then the claim is true.
Logic
Logic is the study of formal validity. We try to
find all the valid logical forms.
That way, if we ever find an argument that has
one of those forms, we will know for sure that it
is valid.
Modern Logic
It wasn’t until recently
that we (or a German
mathematician named
Gottlob Frege) found a
way to find all the valid
logical forms. This is the
logic we learn about
today.
The Limits of Logic
Logic isn’t the entire story. It doesn’t have
anything to say about the good arguments that
are not formally valid, and it can’t identify bad
arguments.
There’s also another kind of “goodness” for
arguments: a sound argument is valid and its
premises are true. But logic alone can’t tell us
what’s true.
For Next Class
Go to the course website:
http://michaeljohnsonphilosophy.com/ccc8001logic-and-critical-thinking-2014/
Read the reading for next time.