The document outlines the importance of studying logic and logical reasoning for critical thinking and forming valid arguments. It defines various types of arguments, such as inductive, deductive, and analogical, and explains the structure of categorical propositions and syllogisms. Additionally, the document covers concepts like contradictories, contraries, and the creation of equivalent propositions.

1. UniT Vi
Logical
Reasoning
Presented by

2. Logic and Logical Reasoning:
Why should we study logic?
• Critical thinking and analysis
• To make strong and valid arguments
• One of the bases of research
LOGICAL REASONING - "A scientific way of
thinking about ideas". (Cambridge dictionary)
LOGIC - Set of principles governing correct/reliable
reasoning.
It creates coherence.
An Introduction

3. • A statement supported by evidences / facts
• Its structure includes two parts :
Argument:
Meaning and Structure

4. A and B are the premises
C is the conclusion
A. Public libraries provide learning
resources for all ages.
B. They provide safe spaces for people
to read, study and gather.
C. Therefore, public libraries should be
funded in every community.
A. John is armed.
B. He is dangerous.
Examples
A is the premise
B is the conclusion

5. Forms of
argument
CAUSE AND EFFECT ARGUMENT
INDUCTIVE ARGUMENT
DEDUCTIVE ARGUMENT
ABDUCTIVE ARGUMENT
ANALOGICAL ARGUMENT

6. • Statements are arranged from specific
observations to general rule
• The conclusion may not always be valid
as the observations can be limited
Inductive
Argument
Eg.
Premises:
We have seen 100 roses.
All of them were pink.
Conclusion:
All roses are pink.

7. • Statements are arranged from general to
specific.
• Truth of the premises guarantees the truth of
the conclusion.
Deductive
argument
Eg. Premises:
All humans are mammals.
All women are humans.
Conclusion:
All women are mammals.

8. • Arguing that because two things are similar,
what is true of one is also true of the other.
• Can be fallacious
Analogical
argument
Eg.
Premises:
Elephants are mammals.
Dolphins are mammals.
Elephants have tusks.
Conclusion:
Thus, dolphins also have
tusks.

9. • What may happen if certain conditions are
present? (Cause>Effect)
• Making predictions / forecasts
CAUSE AND EFFECT
argument
Premises:
There is a high shortage of food due to the increased
death of plants
The water bodies are drying up.
Conclusion:
The common cause of these two effects is “there is a
drought”.
• Why something happened? (Effect>Cause)
• Finding the reason
Eg.
Premise:
It has not rained for one
year.
Conclusion:
A drought will occur.

10. A statement in an argument, consisting of:
Categorical Proposition
A quantifier
A word that represents the quantity
(All, some, no)
Subject term
The first category
Predicate term
The second category
Copula
Link word that connects the subject
and the predicate
(is, is not, are, are not)

11. Properties of a Categorical Proposition
The use of a quantifier to signify the quantity of the subject term.
All roses are flowers.
No roses are flowers.
Some roses are/aren't flowers
Whether the proposition asserts or denies the overlap between the two
categories.
All roses are flowers.
No roses are flowers / Some roses are not flowers

12. Types of Categorical Propositions

13. An argument consisting of
3 categorical propositions.
Categorical
Syllogism
Premises:
All mammals have tails.
All dogs are mammals.
Conclusion:
All dogs have tails.
MAJOR TERM : Predicate term of the
conclusion
MINOR TERM : Subject term of the
conclusion
MIDDLE TERM : Present in both the
premises
All the three terms occur
twice in the syllogism

14. • Way of representing the arrangement of
the three propositions.
• 64 moods - 4 are first figures
• Barbara, Celarent, Darii, Ferio
Mood
No heroes are cowards. E
Some soldiers are cowards. I
Thus, some soldiers are not heroes. O

15. Figure
Used to understand the position of the middle term
in the categorical syllogism.
Figures of the four moods : Barbara, Celarent,
Darii, Ferio

16. Contradictories
• If one is true, the other is
false.
• Both cannot be true/false
together.

17. Contraries
• If one is true, the other
should be false.
• Both can be false.

18. Sub-contraries
• If I is true, O is
doubtful.
• If I is false, O is true.
• Both can be true.

19. Subalterns
• If A/E is true, I/O is true
• If I/O is true, A/E
may or may not be true.

20. Valid Classical Square of Opposition

21. Equivalence in Propositions
Ways of creating equivalents
Equivalent propositions are those which mean the same.
Eg. All women are mammals.
No woman is a non - mammal
Switch the positions of the S and P terms.
Switch the positions of S and P terms and
replace universal with particular.
Change the quality and
replace the P term with its complement.
Switch the position of S and P terms and
replace both with their complements.

22. Connotation and Denotation of terms
Denotation Connotation
Dove A white bird
Olive branch Branch of an olive tree
Monday Blues A colour
Exam fever An immune response
A symbol of peace
Attempt to compromise / end conflict
Feeling bored to work after a weekend
Fear of exam
Straightforward / dictionary
meaning
Symbolic / metaphorical / idiomatic
meaning