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003 Deduction & Induction (I)

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UGED1111B LOGIC:
DEDUCTION & INDUCTION (I)
2019-20, Summer
Sapphires, WONG Sin Ting
Tree Hole for UGED1111B
2
Agenda
3

Types of Argument
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

Deductive Arguments and Inductive Arguments
Possibilities
Types of Proposition
Types of Argument
4

Deductive Arguments (演繹論證)
◼
◼
A deductive argument incorporates the claim that its
conclusion is impossible to be false if all its premises are
true.
The conclusion of a deductive argument can be
conclusively supported by its premises.
Deductive Arguments
5
Example 1
Example 2
1. All Disney animated movies are great.
2. Coco is a Disney animated movie.
1. 從來是指三次。
2. 你三次不接女朋友電話。
3. Coco is great.
3. 你從來不接女朋友電話。
Types of Argument
6

Inductive Arguments (歸納論證)
◼
◼
An inductive argument incorporates the claim that its
conclusion is improbable to be false if all its premises are
true.
The conclusion of an inductive argument can be strongly
supported by its premises.
Inductive Arguments
7
Example 1
Example 2
1. The sun rose from the east today.
2. The sun rose from the east yesterday.
︙
1.上次也是我錯。
2.今次也是我錯。
3. The sun will rise from the east
tomorrow.
3. 永遠都是我錯!
Types of Argument
8

In short, a deductive argument can guarantee the truth
of its conclusion by the truth of its premises, while
an inductive argument cannot.
Conclusion
Conclusion
Content of premises
Deductive Argument
Content of premises
Inductive Argument
Types of Argument
9
Peter Pan
Inside Out
Sleeping Beauty
The Lion King
Coco
Frozen
Aladdin
Mulan
Lady and the Tramp
Dumbo
Zootopia The Aristocats
Cinderella
Tangled
Monsters, Inc.
Ratatouille
The Little Mermaid
Bambi
Beauty and the Beast
Deductive Argument
1. All Disney animated movies are great.
2. Coco is a Disney animated movie.
3. Coco is great.
Types of Argument
10
Today
1. The sun rose from the east today.
2. The sun rose from the east yesterday.
︙
3. The sun will rise from the east
tomorrow.
Tomorrow
Yesterday
1 day before
yesterday
3 day before
yesterday
4 day before
yesterday
2 day before
yesterday
5 day before
yesterday
6 day before
yesterday
n day before
yesterday
Inductive Argument
Possibilities
11

Technological Possibility
◼

Physical Possibility
◼

Do not exceed our current technological constraints.
Do not exceed our physical constraints.
Logical Possibility
◼
Do not exceed our logical constraints.
Possibilities
12

Technological Possibility
◼
Do not exceed our current technological constraints.
?
Possibilities
13

Physical Possibility
◼
Do not exceed our physical constraints.
Possibilities
14

Logical Possibility
◼


Do not exceed our logical constraints.
Basically, everything that currently exists in our world
is logically possible.
What is logically impossible?
Circle-square??
Possibilities
15

What is a circle-square?
Circle
Circle-square??
Square
A circle-square is logically impossible, as it violates the law of non-contradiction.
Possibilities
16

Summary
Circle-square
Move faster than light.
Logical Possibility
Physical Possibility
Technological Possibility
Westworld’s robots
32GB USB flash drive
Types of Proposition
17

Tautological proposition
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
Self-contradictory proposition
◼

A proposition that is necessarily true.
A proposition that is necessarily false.
Contingent proposition
◼
A proposition that is neither necessarily true nor
necessarily false.
Types of Proposition
18

Tautological proposition
◼
A proposition that is necessarily true.
Not possible to be false
EXAMPLE
 這球十二碼,要麼進,要麼不進。
 All bachelors are unmarried.
 如果梁振英是前任行政長官,則上一任行政長官是梁振英。
 It is false that some circles are not round.
It’s necessarily false!
Types of Proposition
19

Self-contradictory proposition
◼
A proposition that is necessarily false.
Not possible to be true
EXAMPLE
 這球十二碼既進亦不進。
 Some circles are not round.
 梁振英是前任行政長官,但上一任行政長官並不是他。
 It is false that all bachelors are unmarried.
It’s necessarily true!
Types of Proposition
20

Contingent proposition
◼
A proposition that is neither necessarily true nor
necessarily false.
EXAMPLE
 France is the FIFA World Cup 2018 Champion.
contingently true
 《降魔的2.0》是無綫電視目前的八點半檔連續劇。
 It is compulsory for Hong Kong students to wear the veil to school. contingently
false
 現任香港特別行政區行政長官是曾俊華。
Exercise (3)
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
Determine the types of the following propositions:
References
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Copi, I., Cohen, C., & McMahon, K. (2011). Introduction to Logic (14th ed. /
Irving M. Copi, Carl Cohen, Kenneth McMahon ed.). Upper Saddle River, NJ:
Pearson Education.
Hurley, P. (2015). A Concise Introduction to Logic (12th ed.). Australia ; Stamford,
Ct.: Cengage Learning.
Lau, J. (2011). An Introduction to Critical Thinking and Creativity : Think More,
Think Better. Hoboken, N.J.: Wiley.
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