Introduction to Critical Thinking

Introduction to
critical thinking
by
Nalaka Gamage
Aurora Computer Studies
(auoracs.lk)
Aurora Computer Studies 1

Agenda
• What is critical thinking?
• How to practice critical thinking?
Aurora Computer Studies (auroracs.lk) 2

What is critical thinking?

What is critical thinking?
• Critical thinking is the ability to think
clearly and rationally about what to do
or what to believe.

What is not critical thinking?
• Mere criticize everything
• Thinking a lot

What hinder critical thinking
• Lack of awareness/practice of rational
(logical) thinking
• Personal biasness
• Cultural biasness
• Intellectual arrogance
• Intellectual laziness
• Black & white thinking

Attribute of critical thinkers
• Rational
• Think extra yard than others
• Demand reasoning
• Open minded
• Ask right questions

Attribute of critical thinkers (con.)
• Do not take anything for granted
• Do not jump into conclusions
• Do not fear challenging
politically/culturally dominant views

How to practice critical
thinking?

How to do critical thinking?
1. Do careful, intentional thinking
o Fully evaluate all parts of argument/claim
2. Analyze & evaluate each piece of the
argument
o Identify facts and opinions
o Evaluate the opinions
3. Use of reason or logic to check the validity
4. Check truthfulness of each fact to see if it is a
sound argument
5. Application/test with real world scenarios to
verify

Fact vs. Opinion
Fact
• A statement of fact can be proved TRUE
or FALSE using standard knowledge
o An observable or obvious thing
o It has been proved by scientific experimentation
o Can be deduced by formal logic
• Example
o Earth is round
o Smoking causes cancer
o There is a force towards the earth

Fact vs. Opinion
Opinion
• A statement of opinion is what someone
believes or thinks
o He must provide enough evidence to prove his opinion
• Called burden of proof
o We have to test if that opinion is valid or not
o If we do not accept the opinion we must show the fault in the
opinion
• We do not have to prove that opinion is false
o We may or may not provide alternative opinion
• Example
o There is life after death
o Mr. X is a better leader than Mr. Y

Problem solving techniques
• Deductive Reasoning
o Best approach 
• Inductive Reasoning
o There are situations to be used
o Use with care 
• Abductive Reasoning
o Wrong approach
o Use with care 

Deductive reasoning

Deductive Reasoning
• Derive logically necessary conclusion
from given premises/ assumptions

How to come to judgements?
• Using formal logic
o Example:
X > 4
y > x
Therefore y >4
• Using scientific knowledge
o Example
• Removing oxygen will extinguish fire

What is an argument?
• An argument is set of assumptions/
premises followed by a conclusion
• Example:
Socrates is a philosopher. (Assumption)
All philosophers like thinking. (Assumption)
Therefore Socrates likes thinking. (Conclusion)

Outcome of an argument
Argument
Invalid
Valid
Sound

What is a valid argument?
• An argument is said to be valid if the
conclusion is logically true, whenever all
the assumptions/premises are true
• Example
o Valid argument
If there is an earthquake, the detector will send a
message.
No message has been sent.
So there was no earthquake.
o Invalid argument
Whenever Anil is here, Kumar is also here.
Anil is not here.
So Kumar is not here.

What is sound argument?
• If an argument is valid and all the
assumptions are found/proved to be
correct, then the argument is said to
be sound.
• We must accept only the sound
arguments!

Inductive reasoning

Inductive Reasoning
• Use patterns of concrete instances to
arrive at a conclusion
• It’s a way of generalization through
observation and careful systematic
analysis

How to come to judgements?
• By analyzing results of empirical data
using concepts of statistics and
probability
o Example:
Is the value considerably higher than average for a
sample with particular feature

Inductive Reasoning - caution
• Use of smaller sample may lead to
false conclusion
• What is your visibility may be too
narrow

Inductive Reasoning - caution
What you have seen
is not close to reality
in general.

Abductive reasoning

Abductive Reasoning
• Abductive reasoning allows inferring a as an
explanation of b
• As a result, abduction allows the precondition a
to be adduced from the consequence b (i.e.
effect to cause)
• Deductive reasoning and abductive reasoning
thus differ in the direction in which a rule like " a
entails b is used for inference.
Incomplete
observation
Best prediction
(May be true)

Abadductive Reasoning - caution
• Considerable risk of inferring wrong
cause
• You may infer A as the cause, whereas
actual cause might be C in this case
A
B
C
D
.
.
P
Q
R
.
.

Overview of reasoning
General
rule
Specific conclusion
(Always true)
Specific
observation
General conclusion
(May be true)
Incomplete
observation
Best prediction
(May be true)
Deductive Reasoning
Inductive Reasoning
Abductive Reasoning

References
• http://philosophy.hku.hk
• https://en.wikipedia.org/wiki/Critical_t
hinking

You may also like following
• If vs If and only if
• Science, philosophy, religions and
myths

Thank You !
Presented by
Nalaka Gamage
Aurora Computer Studies
(auoracs.lk)
32

"We are what we repeatedly do.
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but a habit."
~ Aristotle

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