FINAL LOGIC POWER-1-1.pptx its the best slide to read

1. Chapter One- Introducing to Philosophy
2. Chapter Two- Basic Concepts Of Logic
3. Chapter Three- Logic And Language
4. Chapter Four- Basic Concepts of Critical
Thinking
5. Chapter Five- Informal Fallacies
6. Chapter Six- Categorical Propositions

Chapter One
Introducing Philosophy

 Questions for Discussion
1.What is philosophy?
2.Why is defining philosophy accurately/ precisely so
difficult ?
3.What is (love of) wisdom and who is wise?
4.What are the features of philosophy
5. What is the methodological difference between
philosophy and other sciences?
6.What are the branches of philosophy…….
7.What is the importance of learning philosophy?

Basic Features of Philosophy
Philosophy is:
set of views or beliefs about life and the universe
process of reflecting and criticizing most deeply
held conceptions and beliefs
rational attempt to look at the world as a whole
logical analysis of language and clarification of
the meaning of words and concepts
group of perennial problems where philosophers
always have sought to answers.

 Core branches of Philosophy
Philosophy has different primary and secondary branches
Metaphysics- philosophical study of reality/existence
Epistemology - philosophical study of knowledge/truth
Axiology- philosophical study of value/worth of sth.
Logic- study of argument/ reason

1. Metaphysics
 Etymologically: derived from the Greek words “meta” mean
s (―beyond, ―upon or ―after) and physika, means (―physi
cs)---Literally to mean ‘things after the physics’
 studies the ultimate nature of reality
 seek an irreducible foundation of reality where knowledge c
an induced/deduced
 Deals with issues of
 Reality God, freedom, soul/immortality
 the mind-body problem, form and substance
 relationship, cause and effect relationship

Here are some of the questions that Metaphysics primarily
deals with:
What is reality?
What is the ultimately real?
What is the nature of the ultimate reality?
is it one thing or is it many different things?
Can reality be grasped by the senses, or it is
transcendent?
What makes reality different from a mere appearance?
What is mind, and what is its relation to the body?
is there a cause and effect relationship between reality
and appearance?
Does God exist, and if so, can we prove it?
Metaphysical questions are the most basic to ask because they
provide the foundation upon which all subsequent inquiry is
based

 Metaphysical questions may be divided into four subsets or a
spects:
I. Cosmological Aspect:
 study of theories about the origin, nature, and developme
nt of the universe as an orderly system
 Cosmological questions
• How did the universe originate and develop?
• Did it come about by accident or design?
• Does its existence have any purpose
II. Theological Aspect
 part of religious theory that deals about God
 Theological question
• Is there a God?
• If so, is there one or more than one?
• What are the attributes of God?
• If God is both all good and all powerful, why does evil exist?
• If God exists, what is His relationship to human beings and the rea
l ‘world of everyday life?

III: Anthropological Aspect
• deals with the study of human beings
• Anthropological questions
 What is the relation between mind and body?
 Is mind more fundamental than body, with body dep
ending on mind, or vice versa?
 What is humanity‘s moral status?
 Are people born good, evil, or morally neutral?
IV: Ontology
 Study the ultimate nature of reality/existence
 Ontological questions
• Is basic reality found in matter or physical energy
• is it found in spirit or spiritual energy?
• Is reality orderly and lawful in itself, or
• is it merely orderable by the human mind?

2. Epistemology
 Derived from Greek words --episteme, meaning ― knowledg
e, understanding, and logos, meaning ―study of - literary to
mean the study of truth/knowledge
 Deals with nature, scope, meaning, and possibility of knowle
dge
 deals with issues of knowledge, opinion, truth, falsity, reason
, experience, and faith
 Deals with the dependability of knowledge and the validity o
f sources
 Hence, the study of knowledge Involves three main areas
 The source of knowledge –ways to knowledge
 Nature of the knowledge-
 The validity of the knowledge

The following are among the questions/issues with which
Epistemology deals:
What is knowledge?
What does it mean to know?
What is the source of knowledge? Experience? Reason?
Or both?
How can we be sure that what we perceive through our
senses is correct?
What makes knowledge different from belief or
opinion?
What is truth, and how can we know a statement is
true?
Can reason really help us to know phenomenal things
without being informed by sense experiences?

 Epistemology seeks answers to a number of fundamental iss
ues
 whether reality can even be known
 whether truth is relative or absolute
 Whether truth is subjected to change or not
 The other major aspect of Epistemology is about the sources
of human knowledge
 Empiricism----------Sense Experience
 Rationalism- -------Reason /Thought
 Intuition- -----------Direct apprehension
 Revelation- ---------Supernatural being(from God)
 Authority- ----------Expertise/professionals

1. Empiricism
 knowledge appears to be built into the very nature of human
experience
 Sensory knowing is immediate and universal
 Weakness
 data obtained from human senses is incomplete and u
ndependable.
i.e. Fatigue, frustration, and illness may distort and
limit sensory perception
 there are inaudible and invisible things that can not b
e identified by sense
 Advantage of empirical knowledge
 many sensory experiences and experiments are open t
o both replication and public examination

2. Rationalism
 Reason is source of knowledge
 emphasis on capability of humanity‘s power of thought a
nd the mind
 humans are capable of arriving at irrefutable knowledge i
ndependently of sensory experience
 Senses alone cannot provide consistent universal, valid ju
dgments
 Data obtain through senses are raw material-k/dge
 people have the power to know with certainty various tru
ths about the universe that the senses alone cannot give

Intuition
direct apprehension(grasping) of knowledge
Not derived from reasoning or sense perception
immediate feeling of certainty OR sudden flash of
Insight
source of both religious and secular knowledge
Source for many scientific advancements -
confirmed by
experimentation
The weakness or danger of intuition
When it used alone it may
•goes astray very easily
•lead to absurd claims

4. Revelation
Primary source of knowledge in religion
presupposes a transcendent supernatural reality
Used as omniscient source of information
The truth revealed is absolute and uncontaminated
information
Limitation
Knowledge can be distorted through time
Accepted by faith and cannot be proved or disproved
empirically
5. Authority :accepted as true because it comes from experts
N.B: one source of information alone might not be capable of
supplying people with all knowledge. Hence , a complementary
/Combine use of these sources is necessary to enhance our
knowledge.

3. Axiology
 Derived from Greek words - Axios, meaning ―value, worth
, and ―logos, meaning ―study to mean the study of value/
worth of something
 Axiology asks the philosophical questions of values that de
al with notions of what a person or a society regards as good
or preferable such as:
What is a value?
Where do values come from?
How do we justify our values?
How do we know what is valuable?
What is the relationship between values and knowledge?
What kinds of values exist?
Can it be demonstrated that one value is better than another?
Who benefits from values?

3. There are Three different area of axiology
I. Ethics
II. Aesthetics
III. Social/political philosophy-

I. Ethics : philosophical study of principles used to judge
human actions as good/bad/right/wrong
•Normative ethics:
Teleological Ethics
Deontological Ethics
Virtue Ethics
•Meta- ethics:
•Applied Ethics:

II. Aesthetics
 Aesthetics is the theory of beauty
 studies particular value of our artistic and aesthetic
experiences.
 deals with beauty, art, enjoyment, sensory/emotiona
l values, perception, and matters of taste and sentim
ent
 The following are typical Aesthetic questions:
•What is art?
•What is beauty?
•What is the relation between art and beauty?
•What is the connection between art, beauty, and
truth?

III. Social/Political Philosophy
studies about of the value judgments operating in a civil society
The following questions are some of the major Social/Political
Philosophy primarily deals with:
What economic system is best?
What form of government is best?
What is justice/injustice?
What makes an action/judgment just/unjust?
What is society?
Does society exist? If it does, how does it come to existence?
How are civil society and government come to exist?
Are we obligated to obey all laws of the State?
What is the purpose of government?

 Importance of learning philosophy
Intellectual and behavioral independen
ce
Reflective Self-Awareness
Flexibility
Tolerance
Open-Mindedness
Creative and Critical Thinking
Conceptualized and well-thought-out v
alue systems
helps us to deal with the uncertainty of
living

FINAL LOGIC POWER-1-1.pptx its the best slide to read

Chapter2
Basic Concepts of Logic

Chapter Objectives:
 after the successful completion of this chapter, you
will be able to:
Understand the meaning and basic concepts
of logic;
Understand the meaning, components, and
types of arguments; and
Recognize the major techniques of
recognizing and evaluating arguments.

Brainstorming question
1.What is logic?
2.What is the significance of learning logic for you?

Logic:
Comes from Greek word ’logos’ to mean discourse",
"reason", "rule
a science that evaluates arguments
study of methods and principles of correct reasoning
develop the method and principles for evaluating argum
ents
primary tool philosophers use in their inquiries
attempt to codify the rules of rational thought
in logic we study reasoning itself:
forms of argument
general principles and
particular errors
along with methods of arguing

Question 2
1. What is argument, statement ,premise a
nd conclusion ?

Argument ,premise and conclusion
Argument is the primary focus of logic
Argument is group of statements
One/more of which claimed to provide evidence
one of the other follows the evidence
From The definition
An argument is a group of statements
The statement/s divided into premise(s) and conclusion
Statement :declarative sentence with truth-value
Argument always attempts to justify a claim i.e.
• claim that the statement attempts to justify -C
• statements that supposedly justify the claim -P
Therefore, An Argument is always composed of P & C

Sentences: group of words or phrases that
enables us to express ideas meaningfully
sentence: may or may not have truth value
Sentences of the following type are not
statements
• Would you close the window? (Question)
• Let us study together. (Proposal)
• Right on! (Exclamation)
• I suggest that you to read philosophy
texts. (Suggestion)
• Give me your ID Card, Now! (Command)

Examples
o All Ethiopians are Africans.
Tsionawit is an Ethiopian
Therefore, Tsionawit is an African
o Some Africans are black
Zelalem is african
Therefore, Zelalem is black
o All crimes are violation of law
Theft is a crime
Therefore ,theft is a violation of law
o Some crimes are misdemeanor
Murder is a crime
Therefore ,murder is misdemeanor

 Identifying conclusion and premise
 Logic: evaluates and analyses arguments
 important tasks in the analysis of arguments is to distinguis
hing premises &conclusion
 two criteria are applied to identify C&P
1. looking at an indicator word
 Premise indicators words :
o Since, Because, As indicated by, May be inferred from
o Owing to, in as much as, in that, for the reason that
o given that, seeing that, as, for…etc.
 Conclusion indicators words :
o Therefore, Hence, So, Wherefore, Accordingly
o Whence, It follows that, It must be that, Thus
o As a result, We may infer, Consequently

Examples
o Women are mammals. Zenebech is a woman. Therefore, Zenebec
h is a mammal.
o You should avoid any form of cheating on exams because cheat
ing on exams is punishable by the Senate Legislation of the Uni
versity.
o The development of high temperature super conducting materi
als is technologically justiﬁable, for such materials will allow el
ectricity to be transmitted without loss over great distances, and
they will pave the way for trains that levitate magnetically.
o A Federal government usually possesses a constitution, which g
uarantees power sharing between the federal and regional gove
rnments. This implies that distribution of power is the salient fe
ature of any federal government.
.

2. Inferential claims
 It refers to the reasoning process expressed by the ar
gument which exist between the premises and the con
clusion of arguments.
 Use this If an argument contains no indicator words a
t all
 To identify P& C responding to either of the followin
g questions.
Which statement is claimed to follow from othe
rs?
 What is the arguer trying to arrive at /prove?
What is the main point of the passage?
 The answers to these questions should point to the co
nclusion.

Example:
o Our country should increase the quality and quantity of its mi
litary. Ethnic conflicts are recently intensified; boarder conflic
ts are escalating; international terrorist activities are increasin
g.
o Socialized medicine is not recommended because it would resu
lt in a reduction in the overall quality of medical care available
to the average citizen. In addition, it might very well bankrupt
the federal treasury. This is the whole case against socialized m
edicine in a nutshell.
o The space program deserves increased expenditures in the yea
rs ahead. Not only does the national defense depend up on it, b
ut the program will more than pay for itself in terms of technol
ogical spinoffs. Furthermore, at current funding levels the pro
gram cannot fullﬁll its anticipated potential.

Answer:
o P1=Ethnic conflicts are recently intensified.
P2=Boarder conflicts are escalating.
P3=International terrorist activities are increasing.
C= Thus, the country should increase the quality and
quantity of its military.
o P1=Socialized medicine result in a reduction in the overall
quality of medical care available to the average citizen.
P2=Socialized medicine might very well bankrupt the
federal treasury.
C= therefore, Socialized medicine is not recommended

Answer:
o P1=The national defense is dependent up on the space
program.
P2=The space program will more than pay for itself in
terms of
technological spinoffs.
P3=At current funding levels the space program
cannot fullﬁll
its anticipated potential.
C=The space program deserves increased
expenditures in the
years ahead.

Self check Exercises
BOOK: concise introduction to logic
1.page 7 Exercise 1.1. LC (I)- identifying premise a
nd conclusion
2.Page 13 exercise 1.1. III- definition of terms
3.Page 13 exercise 1.1. IV- TRUE/False

 Techniques of Recognizing Arguments
All passages may not contain an argument.
To distinguish argument from non- argument
1. Existence of Indicator words
2. Existence of Inferential claim between statements
3. Know Typical Non-argumentative passages

1. Existence of indicator words
oSince Edison invented the phonograph,
there have been many technological
developments.
oSince Edison invented the phonograph,
he deserves credit for a major
technological development

2. Inferential claim
a passage contains an argument if it purports to prove
something; if it does not do so, it does not contain an
argument.
Any passage is labeled as an argument if and only if it fulfills
the following two conditions:
1. At least one of the statement must claim to provide
reason or evidence
2. There must be a claim that something is followed from
the evidence
Questions for discussion
o with in an argument , is it mandatory for the Premises to pres
ent actual evidence or true reasons to the conclusion?
o Which one should be mandatory for a passage to be an argu
ment: factual claim or inferential claim?

It is not necessary/ mandatory for the prem
ises to present actual evidence or true reaso
ns
But at least the premises must claim to pres
ent evidence or reasons, and there must be a
claim that the evidence or reasons support o
r imply something

3. Non-argumentative passages
Warning: contains cautionary advices
Piece of advice : contain counseling or guidelines
belief/ opinion: belief of someone on different events
Report: convey information about events
Expository passage: topic and sub topic sentences
Illustration: clarifying instances of different matters
 Explanation: shed light on certain phenomenon
Conditional Statements: express cause and effect of
events

Explanation and argument:
In explanation
two components: Explanans and Explanandum
Intends to shed light on some event
The event in question is usually accepted as a fact
Example
Cows digest grass while humans cannot, because their digestiv
e systems contain enzyme not found in humans.
Argument
Premise ==== Accepted facts
Claimed to prove the
Conclusion
Explanations
Explanans
Claimed to shed light on
Explanandum =====Accepted facts

 Conditional Statements and argument
 an “if…, then…”statement,
 has two component: “Antecedent and Consequent’’
 if antecedent then consequent or Consequent If antecedent
 The relation between conditional statements and argumen
ts may now be summarized as follows:
– A single conditional statement is not an argument.
– A conditional statement may serve as either the premise
or the conclusion
– The inferential content of a conditional statement may be
re-expressed to form an argument.
example
If you study hard ,then you will score good grade.

A---Sufficient condition …B:
whenever the occurrence of ‘A’ is needed f
or the occurrence of ‘B
A is a sufficient condition for B; if A occurs,
then B must occur.
A….Necessary condition….B:
whenever B cannot occurred in the absenc
e of A.
A is a necessary condition for B; if B occur, t
hen A must occur.

Self check Exercises
BOOK: concise introduction to logic
1.page 25 Exercise 1.2. LC (I)- identifying argument
and none argument
2.Page 32 exercise 1.2. Iv- definition of terms
3.Page 32 exercise 1.2. V- TRUE/False

 Every argument involves an inferential claim
 Depending on the inferential relation between p & c
1. deductive argument
2. Inductive argument

1. Deductive Arguments
 Its impossible for the conclusion to be false given that
the premises are true
 conclusion follows the premise with necessity
 involve necessary reasoning.
 Example 1: All philosophers are critical thinkers.
Socrates is a philosopher
Therefore, Socrates is a critical thinker
 Example2: All African footballers are blacks
Messi is an African footballer
It follows that, Messi is black

2. Inductive Arguments
 it is improbable for the conclusion to be false given that
the premises are true.
 the conclusion follow the premise only with probability
 It involves probabilistic reasoning.
• Example1: Most African leaders are blacks.
Mandela was an African leader
Therefore, probably Mandela was black.
• Example2: Almost all women are mammals.
Hanan is a woman.
Hence, Hanan is a mammal.

 Differentiating Deductive and Inductive Arguments
 criteria to differentiate DA & IA
1. The occurrence of special indicator words
• Certainly, Necessarily, Absolutely, Definitely=deductive
• Probable‖ , Improbable, Plausible,‘ Implausible,‘‘ likely,
unlikely===Inductive argument
2. The actual strength of the inferential link between premises
and conclusion
• All Ethiopian love their country.
Debebe is an Ethiopian.
Therefore, Debebe loves his country.
• majority of Ethiopian are poor.
Alamudin is an Ethiopian.
Therefore, Alamudin is poor

3. The character or form of argumentation the arguers use
 Some typical deductive arguments
arguments based on Mathematics
argument based on definition
categorical syllogism
Hypothetical syllogism
Disjunctive Syllogism
 Some typical Inductive Arguments
Arguments of Prediction
argument from analogy
argument from authority
inductive generalization
argument based on signs
argument based on causation

Instances of deductive argument
1. arguments based on Mathematics
 C depends on arithmetic/ geometric computation
 Exception: arguments of statistics =inductive argument
Example:
 you can measure a square pieces of land and after
determining it is ten meter on each side conclude that its
area is a hundred square meter.
 The sum of two odd numbers is always even. Thus, the
sum of 3 and 9 is an even number.
 Since triangle A is congruent with triangle B, and
triangle A is isosceles, it follows that triangle B is
isosceles.

2. Arguments based on definition:
 conclusion depend on the definition of some words or
phrase used in the premise
Example:
• Angel is honest; it is follows that Angel tells the truth.
• Kebede is a physician; therefore, he is a doctor
• God is omniscient, it follows that He knows everything

3. Categorical syllogism:
 statement begins with one of the words all, no and some
Example:
• All Egyptians are Muslims. No Muslim is a Christian. Hence
, no Egyptian is a Christian.

4. Hypothetical Syllogism
 have conditional statement for one or both of its premises
 “If…then statement.
IF A then B.
If B then C.
Therefore , If A then C.
Example:
P1=If you study hard, then you will graduate with Distinction.
P2=If you graduate with Distinction, then you will get a
rewarding job.
C=Therefore, if you study hard, then you will get a rewarding
job.

5. Disjunctive Syllogism :
 begin with an “Either…or …” phrase
 Either A or B. not A .Therefore B
Example
Rewina is either Ethiopian or Eritrean.
Rewina is not Eritrean.
Therefore, Rewina is Ethiopian
Either Italy or Ethiopia won the military incident of Adwa.
Italy did not win the military incident of Adwa.
Therefore, Ethiopia won the military incident of Adwa

 Instances of Inductive Argumentative Forms
Arguments of Prediction
Inductive generalization
Argument from authority
Argument based on certain signs
Argument from analogy
 Argument based on causation

1. Prediction
• premises deals with some known event in the present or the
past and the conclusions moves beyond this event to some
event to relative future
Example
• one may argue that because certain clouds develop in the
center of the highland, a rain will fall within twenty-four
hours.
• It has been raining for the whole day of this week. This shows
that it will rain for the coming week.

2. An argument from analogy:
 depends on the existence of similarity between two things or
state of affairs
 certain conditions that affects the better- known situation is
concluded to affect the lesser known situation
For instance
• Computer A is manufactured in 2012; easy to access and
fast in processing; Computer B is also manufactured in
2012; easy to access. It follows that, Computer B is also fast
in processing.

3. An inductive generalization:
 proceeds from the knowledge of a selected sample to claim
about the whole group
 Claim: Since the sample have a certain (X) characteristics,
all members of the group have the same (X) characteristics.
For example
• one may argue that because three out of four people in a
single prison are black, one may conclude that three-fourth
of prison populations are blacks.

4. An argument from authority:
• conclusions rest upon a statement made by some presumed
authority or witness
for instance:
• A lawyer may argue that the person is guilty because an eye
witness testifies to that effect under oath
• all matters are made up of a small particles called ―quarks
because the University Professor said so.

5. Arguments based on sign:
• Proceeds from the knowledge of a certain sign to the
knowledge the sign symbolizes.
For instance
• after observing ‗No Parking‘ sign posted on the side of a
road, one may infer that the area is not allowed for
parking.

6. An argument based on causation:
 Depends on instances of cause and effect which can
never be known with absolute certainty
Example
• from the knowledge that a bottle of water had been
accidentally left in the freezer overnight, someone
might conclude that it had frozen (cause to effect ).
• after tasting a piece of chicken and finding it dry and
tough, one might conclude that it had been overcooked
( effect to cause).
• The meat is dry so that it had been over cooked 
effect to cause

Evaluating Arguments: deductive and
inductive
Deductive argument
Valid and invalid
sound and unsound
Inductive argument
Strong and weak
Cogent and un-cogent

Deductive Argument :Validity and soundness
Valid deductive argument
if the premises are assumed true, it is
impossible for the conclusion to be false
conclusion follows the premises with strict
necessity
connection b/n P&C is a matter of certainty
Invalid deductive argument:
if the premises are assumed true, it is possible
for the conclusion to be false.

 validity and Truth value
 No direct relationship b/n validity and truth value of
statements
 Exception: an argument T=P & F=C is always invalid
 Therefore , An argument has the following four possibilities
Of Truth vale combinations
 Validity is not determined by actual truth value of
premise/conclusion rather by FORM
Premise Conclusion Valid Invalid
True True  
False False  
True False X invalid
False True  

 Soundness of deductive argument
 A sound argument is a deductive argument that is valid
and has all true premises.
 Argument is sound if
The argument is valid
It has all actually true P
 if either of these is missed the argument is
unsound

Evaluating Inductive Arguments: Strength, Truth
• strong inductive argument
f they are assumed true, it is improbable for the
conclusions to be false.
conclusion follows probably from the premises
• weak inductive argument
if the premises are assumed true, it is probable for the
conclusions to be false.
Example
• This barrel contains one hundred apples. Eighty apples
selected at random were found tasty. Therefore, probably all
one hundred apples are tasty
• This barrel contains one hundred apples. Three apples
selected at random were found tasty. Therefore, probably all
one hundred apples are tasty.

 Strength and Truth Value
 No direct relationship b/n S/W and truth value of
statements
 Exception: an argument T=P & probably F=C is always
Weak
 Therefore , An argument with :
 Strength and weakness is not a matter of actual truth
value rather DEGEREE
Premise Conclusion Strong Weak
True Pro. True  
False Pro. False  
True Pro. False X Weak
False Pro. True  

 Cogency of inductive argument
 Cogent argument is strong and has all true premises.
 cogent argument has two essential features:
 Should be strong and
 all its premises should be true
 If one of these two conditions is missed, the argument
would be un-cogent.
Example:
Nearly all lemons that have been tasted were sour. Therefore,
nearly all lemons are sour.

Chapter three
Logic and Language

Chapter three
Logic and Language
Function of Language
Cognitive meaning/function
Emotive meaning/function
Examples:
The first written constitution of Ethiopia was formulated in
1931.
However the first federal constitution is effected since 1995.
Death Penalty is the final, cruel and inhuman form of all
punishments where hapless prisoners are taken from their cells
and terribly slaughtered

Intentional and extensional meaning of terms
Terms made up of words - serve as a subject of a
statement
Terms includes:
proper names,
common names
 descriptive phrases
Words - symbols and the entity they symbolize- meaning.
terms have two kind of meaning :
 Intensional meaning
Extensional meanings

 Intentional meaning of terms
 Attribute of the term being connoted
 subjective : vary from person to person.
 To avoid subjective meaning - conventional connotation
 can be expressed in terms of increasing and decreasing
intentions
 Increasing intention:
 each term in the series connotes more attribute
than the one preceding it.(animals, mamals, feline, tiger
Decreasing intention:
each term in the series connotes less attribute than
the one preceding it.

 Extensional [denotative] meaning of terms
 Refers to the members that the term denotes
 remains the same to all but
 may be changed with the passage of time – Empty extension.
 can be expressed in terms of increasing /decreasing extension.
 Increasing extension: each term in the series denotes
more members than the one preceding it(tiger, feline,mamals,
animals
 Decreasing extension: each term in the series denotes less
members than the one preceding it
 Intentional meaning determines extensional meaning of
terms

 Types of definition and their purpose
1. Stipulative definitions
Assign meaning for the first time
 Names are assigned arbitrarily &
caused by new phenomena and developments
Definition/statements doesn’t have truth value
Purpose : simplifying complex expressions
 used to set up new secret codes
Examples:
- Logphobia” means fear of taking logic course.
- A male tiger + female lion =tigon
- Operation Barbarossa – Nazi invasion of USSR
- Operation sunset – Ethio-Eritrea war(1998)

2. Lexical definitions:
It reports the meaning of the word actually exist in
dictionary
Provides Dictionary meaning of terms
Purpose: to avoid ambiguity
Examples:
3. Precise definition:
 Intended to reduce vagueness
 Definition should be appropriate and legitimate to the
context in which the term is employed
Examples
- High” means, in regard to the interest rates, at least two points
above the prime rate
- “Antique” means, at least 100 years old

4. Theoretical definition :
 Assign meaning to a word by suggesting theories
 theoretical definitions provide a way for further
experimental investigations
Example : ‘’Heat” means the energy associated with the random
motion of molecules
5. Persuasive definition
 Purpose: to engender a Un/favorable attitudes
 To influence attitude of reader/ listeners
 Use value laden[emotively charged] words

 Extensional definition techniques
1. Ostensive[demonstrative] technique
Is the traditional way of defining terms
Use pointing as a technique to define terms
Is limited by time and space
2. Enumerative technique
Assign meaning by naming members individually
It can be partial or complete
3. Definition by subclass
Assign meaning by naming the subclass of the class.
it can be partial or complete
Example :Tree” means an Oak, Eucalyptus, olive, juniper

 Intentional definitional techniques
1. Synonyms definition
 The definiens is a synonym of the word being defined
 Single word is highly appropriate
Example :“Obese” Means fat
2. An etymological definition
Assign meanings to a word by disclosing its ancestry
enables us to get the historical details of the word
Example: “Virtue” is derived from Latin virtues- means strength.
3. Operational definition
 gives meaning by setting experimental procedures
It prescribes the operation to be performed
bring abstract Concepts to the empirical reality
Example: A solution is “acid” if and only if litmus paper turned
red when dipped into it.

4. Definition by genus and difference
 To construct this definition
 identify the genus & specific difference
 Most effective of all intentional definitions
Examples:
Species Difference Genus
- “Ice” means frozen water.
- “Father” means a male head of the family

1. Meaning of Critical Thinking
 Critical thinking can be defined as (refers to) :
Involving or Exercising skilled judgment
thinking clearly and intelligently
Wide range of cognitive skills and intellectual disposition
s
oIdentify /classify
oEvaluate
oAnalyze
oUnderstand
oSynthesize
oCriticize arguments and true claims
 Critical thinking is to think Clearly, Actively, fairly, rationall
y, objectively and independently.

John Dewey:
 Critical thinking is active, persistent, careful consi
deration of issues/belief in different grounds
For Robert Ennis:
 Critical thinking is reasonable, and reflective thin
king focusing on decide what you believe or to do
(decision making)
For Richard Paul:
 Critical thinking is model of thinking which focus i
n reflecting on thoughts
 having ability of thinking about one’s thinking and
 consciously aim to improve it.

Critical thinking helps us to:
discovers & overcomes personal preconceptions
or prejudice
formulate & provide convincing reason and justi
fications to
make reasonable/rational decision about what w
e believe
impartially investigate data and facts not swayed
by emotion
arrive at well-reasoned, sound and justifiable co
nclusion

2. Standards of CT
1.Clarity
o Clear understanding of concepts
o Expression should free of vagueness and ambiguity
o CT strive both for clarity of language & thought
2. Precision
o being exact, accurate and careful
o reducing vague and obscures thoughts
o Provide precise answer to precise questions of life
3. Accuracy
o Having correct and genuine information
o CT value truth, accurate and timely information
o Every decision should be made based on true information
o If the input is false information, decision will not be sound

4. Relevance
o It’s an issue of connection
o focus on Significant ideas logical to the issue at hand
o focus should be given to the issue at hand
5. Consistency
o Quality of always behaving in the same way
o following same standards in decisions making
o There are two kinds of inconsistency that we should a
void
- Logical inconsistency
- Practical inconsistency:
6. Logical Correctness
o To think logically it reason correctly
o To draw well-founded conclusions from belief/inform
ation
o Conclusions should logically follow believe or evidenc
e

7. Completeness
o deep and complete thinking to shallow and superfici
al thinking
8. Fairness
o Treat all relevant views alike
o thinking should be based on
fair
open mindedness,
Impartiality and
o thinking should be free
distortion,
Biasedness
Preconceptions,
Inclinations,
Personal interests

3. Principles of Good Argument
1.The Structural Principle
 Use arguments that meet fundamental structural requirem
ent
 Valid form is the First requirement for argument to be goo
d (deductive)
• Don’t use reason that contradict to each other
• Conclusion should follow the premise with strict necessity
Good argument:
o Structurally good form(valid)-
o Premises must be compatible to each other (compatibil
ity principle)
o Conclusion should not contradict with the premises

2. The Relevance Principle
One who argues in favor or against a position……?
 Set forth premise whose Truth provides evidence for the truth of the co
nclusion
 Premise is relevant if its provides logical reason to the conclusion
 basic question:- Does the truth of the premise support the truth of the c
onclusion?
3. The Acceptability Principle
 Premise must provide evidence that can be accepted by a mature, ratio
nal person
 If the reason has the capability to convince a rational person to accept
conclusion
4. The Sufficiency Principle
 Premise provides sufficient reason that outweigh the acceptance of th
e conclusion

5. The Rebuttal Principle
Person should provide effective rebuttal (refutation) to all anticipated se
rious criticisms of an argument raised against it.
good argument effectively refute criticisms raised against it
Ask and answer following questions in applying the rebuttal principle to
an argument.
o What is the strongest side of arguments against the position be
ing defended?
o Does the argument address the counterargument effectively?
o What potentially serious weaknesses exist in the argument rec
ognized by an opponent?
o Does the argument itself recognize and address those possible
weaknesses?
o Does the argument show why arguments for alternative positio
ns on the issue are flawed or unsuccessful?

4. Principles of Critical Thinking
1. The Fallibility Principle
Willingness of participants in an argument to acknowle
dge his/her fallibility
Accept one ‘s own initial view that may not be the most
defensible position on the issue
Consciously accept that your view may be wrong - willi
ng to change your mind
An admission of fallibility is a positive sign for further
discussion, inquiry and fair resolution of the issue
No one is perfect, so everyone must admit imperfection

2. The Truth-Seeking Principle
Participant should be committed to search truth
One should be willing to
o Examine alternative positions seriously
o look for insights and positions of others
o Allow others to present arguments for or against
The search for truth is lifelong endeavor and can be attaine
d if:
o We discuss and entertain the ideas and arguments of fe
llow
o We listen arguments for positions and
o Have willingness to look at all available options
o We encourage criticisms of our own views
So, everyone should have the Willingness to look at all avail
able options

3. The Clarity Principle
Formulations of all positions, defenses, and attacks should be free of any
kind of linguistic confusion
Discussion is successful if it carried on in language that all the parties inv
olved can understand
Expressing in confusing, vague, ambiguous, or contradictory language w
ill not help reach the desired goal
4. The Burden of Proof Principle
Burden of proof rests on the participant who sets forth the position or ar
gument
Participant is logically obligated to produce reasons in favor of his claim
The arguer is Obliged to give logical answer to the why/how questions
Exception: if claim in question is well established or uncontroversial, bur
den to proof rests on the opponents who stands against original argument
But Requesting others to accept your idea without proof/ blaming burde
n to proof to other- ignorance

5. The Principle of Charity
 If the participant ‘s argument is reformulated by an opp
onent, it should be carefully expressed in its strongest po
ssible version (intension of the original argument).
 Opponent has an obligation of interpreting a speaker's s
tatements in the most rational way, considering its best s
trongest possible interpretation of original argument
 But If we deliberately create and then attack a weak ver
sion-uncharitable version- of the original argument, we
will fail to achieve the desirable goal of the discussion
 Good discussion imposes an ethical requirement on thei
r participants and there is practical reason for being fai
r with one another ‘s arguments

6. The Suspension of Judgment Principle
 Suspend judgment about the issue if
o no position is defended by good argument, or
o two or more positions seem to be defended with equal
strength
o one has no good basis (evidence) for making a decisio
n
 To make decision: relative benefits or harm of (consequence)
should also take in to consideration
7. The Resolution Principle
 Issue should be considered resolved if the
o Argument for one of the alternative positions is a structu
rally good
o Argument provides relevant and acceptable ,sufficient re
asons to justify the conclusion
o Argument provides effective rebuttal to all serious critici

Why are issues not resolved? When
oWhen One or more of the parties to the dispute:
has a blind spot: not objective about the issue a
t hand and rational but not psychologically con
vinced by the discussion
have been rationally careless
has a hidden agenda
not being honest with themselves
oare in deep disagreement of underlying assum
ptions

Barriers to Critical Thinking
 Egocentrism
 Sociocentrism
 Unwarranted Assumptions and Stereotypes
 Relativistic Thinking
 Wishful Think
Befits of critical thinking
Individually
Community
Class room

 Argument:
 Argument can be good/bad, depending on the r/p b/ n the
P&C
 Good argument meets all the required criteria
 A good argument:
• Structurally good form
• Has relevant , acceptable & sufficient premise
• Provide an effective rebuttal to all reasonable
 An argument violates the above principles becomes fallacious
 Fallacy:- logical defect or flaw in reasoning process in ana
argument
o (bad) form of the argument
o (bad) defects in the contents of the statements
 Violation of standard argumentative rules or criteria.
 Both deductive and inductive arguments may contain
fallacies
 People may commit fallacy intentionally or unintentionally

 Depending on the kind of the defects they contain:
1. Formal fallacy:
 due to structural defect
 found only in deductive argument with identifiable form
 Easily identifiable by their form
 Hence, deductive arguments with invalid form
Example:
– All tigers are animals. All mammals are animals. Therefore, all tigers
are mammals.
2. Informal fallacy :
 due to bad content
 found in both deductive and inductive arguments
 Cannot be identified through inspection of the form
 Identifiable through detail analysis of content
Example:
• All factories are plants. All plants are things that contain chlorophyll.
Therefore, all factories are things that contain chlorophyll

 Informal fallacies are Classified in to:
1. Fallacies of relevance
have logically irrelevant but psychologically relevant
premise to conclusion
2. Fallacies of weak induction
have logically relevant premise but with no sufficient
evidence
3. Fallacies of presumption
 Premise contains an assumptions which isn't supported
by evidence
4. Fallacies of ambiguity
Conclusion drawn from ambiguous used words and
phrases
5. Fallacies of grammatical analogy
Structurally, looks good argument but has bad content

Fallacy of Relevance
 Premise is logically irrelevant to the conclusion
 but psychologically premise is relevant to the
conclusion
 Conclusion does not follow the premise logically
 Unlike in good argument(genuine evidence) in
fallacy of relevance- emotional appeal
 Hence, connection between P&C is emotional
 It includes fallacies of :
1. Appeal to force- employ threat
2. Appeal to pity- evoke pity
3. Appeal to the people – manipulate desire of peop
le
• bandwagon –-----majority’s choice

4. Against the person
• Ad hominem abusive
• Ad hominem circumstantial
• Ad hominem tu qoque
5. Accident – misapplication of G.R to specific case
6. Straw man –distortion of original argument
7. Missing the point- C misses logical evidence of P
8. Red herring – diverting attention of L/R to ward
new
issue

1.Appeal to force or stick fallacy
 Arguer poses C by employing threats on L/R
 Always involves using threat
• physical (explicit force/threat)
• psychological (implicit force/threat)
 Threat is logically irrelevant to conclusion
Examples :
1. Mr. Kebde you have accused me of fraud and embezzlements.
You have to drop the charge you filed against me. You have to
remember that I am your ex-boss; I will torture both you and y
our family members if you do not drop your case. Got it?
2. Child to playmate: ‘‘Josy in the house’’ is the best show on TV
; and if you don’t believe it, I’m going to call my big brother o
ver here and he’s going to beat you up.

3. Lately there has been a lot of negative criticism of o
ur policy on dental benefits. Let me tell you somethi
ng, people. If you want to keep working here, you ne
ed to know that our policy is fair and reasonable. I
won't has anybody working here who doesn't know t
his
4. Secretary to boss: I deserve a raise in salary for the
coming year. After all, you know how friendly I am
with your wife, and I’m sure you wouldn’t want her
to find out what has been going on between you and
that sexpot client of yours. (Psychological threat)

2. Appeal to Pity
 Support a conclusion merely by evoking pity in one ‘s
audience
 If the arguer succeeds in evoking strong feelings of pity, the
listeners may deceived to accept the conclusion with out
logical evidence
Example:
o The Headship position in the department of accounting should be given to
Mr. Oumer Abdulla. Oumer has six hungry children to feed and his wife d
esperately needs an operation to save her eyesight.
o Taxpayer to judge: Your Honor, I admit that I declared thirteen children a
s dependents on my tax return, even though I have only two. But if you fin
d me guilty of tax evasion, my reputation will be ruined. I’ll probably lose
my job, my poor wife will not be able to have the operation that she desper
ately needs, and my kids will starve. Surely I am not guilty.

 There are arguments from pity, which are reasonable and
plausible which is called argument compassion
 Most society values helping people in time of danger and
 showing compassion and sympathy is a natural response in
some situation.
 If some group of people are in danger, helping out may
require appeal to the compassion
Consider the following argument.
 Twenty children survive earthquakes that kill most people in
the village. These children lost their parents. They are out of
school, and home in the street. Unless we each of us
contribute money, their life will be in danger in the coming
days. We should help these children as much as we can.

3. Appeal to the People
 Naturally, everyone wants to be accepted, loved, and esteemed by
others. However, the problem lies on how to secure this desire.
 Committed when an arguer draw a conclusion by manipulating the desi
re of the people using different techniques
 Arguers illogically attempt to exploit the desire/emotion of the people
for some private motives
 Claim : if you want to be member of the group , accept xyz as true
 Two approaches
o Direct approach
• Arguer address a large group of people, excites the emotions a
nd enthusiasm of the crowd to win acceptance for his or her co
nclusion.
• Objective-----arouse mob mentality
• Individuals in the audience want to share the
excitement and find themselves accepting any number of concl
usions with ever-increasing fervor
• Usually employed by speakers, propagandists, politicians

Indirect approach :
Arguer appeal not at the crowd as a whole but at
individuals separately who have relationship to the
crowd
Used by industries to advertise their product
• Using emotively charged terminologies
• Capability to attract people towards the product
or issue
Three varieties
i.appeal to bandwagon
ii.Appeal to vanity
iii.Appeal to snobbery

i. Appeal to Bandwagon
 Commonly appeals to the desire of individuals to be considered as
part of the group or community in which they are living
 Community or group shares some common values and norms
 Hence, every individual is expected to manifest group conformity to
these shared values
 Bandwagon uses these emotions and feelings to get acceptance for a
certain conclusion
Example: The majority of people in Ethiopia accept the opinion that child
circumcision is the right thing to do. Thus, you also should accept that
child circumcision is the right thing to do.
 In advertising ,the issue is intentionally Attached with majority
section of society– and others are urged to follow the decision of
majority
Example : Of course you want to buy Zest toothpaste. Why, 90 percent of
America brushes with Zest

 Appeal to Vanity
 Arguer associates the product with someone who is admired,
pursued and people
 Claim: if you use the product which is used by some one
respected by the people ,you will be respected too.
Example: BBC may show the famous footballer, Frank Lampard, wearing
Adidas shoe, and says: Wear this new fashion shoe! A shoe, which is
worn only by few respected celebrities! ADIDDAS SHOE!!!
 Appeal to snobbery
 Arguer associates the issue with persons who have high social
status(higher class)
 Claim: ‘if you want to be a member of the selected few, you
should accept XYZ.’
Example: A Rolls Royce is not for everyone. If you qualify as one of the
select few, this (distinguished classic may be seen and driven at
British Motor Cars, Ltd. (By appointment only, please.)

4. Argument against the person
 Normally in a good argument, to achieve collaborative goals arguers are
expected to:
o observe rules of polite conversation
o to trust each other and express their arguments/position clearly
and honestly
o focus on attacking the content of the argument than personality of
opponents
 But arguers focus on attacking personality of opponents than the content
of the argument---against the person fallacy
 Occurred when an arguer discredits an argument by attacking the person
ality of his opponent
 always two arguers
 three forms of against the person:
i. Ad hominem abusive
ii.Ad hominem circumstantial
iii.Tu quoque (you too)

i. Fallacy of ad hominem abusive
 Committed when an arguer rejects an argument by verbally abusing the
personality of his opponent rather than the contents of his opponent’s ar
gument
 second person rejects the first person ‘s argument by verbally abusing t
he first person
 Premise: A is a person of bad character
Conclusion: A‟s argument should not be accepted.
Examples:
• In defending animal rights, Mr. Abebe argues that the government should
legislate a minimum legal requirement to any individuals or groups who w
ant to farm animals. He argues that this is the first step in avoiding unnece
ssary pain on animals and protecting them from abuse. But we should not
accept his argument because he is a divorced drunk person who is unable t
o protect even his own family.
• Mr. Abebe has argued for increased funding for the disabled. But nobody s
hould listen to his argument. Mr. Abebe is a slob who cheats on his wife, b
eats his wife, , and kids, and never pays his bills on time.

ii. Fallacy of ad hominem Circumstantial
Committed when an arguer discredits the argument of his opp
onent by alluding the argument with certain circumstances that
affect his opponents
Easy to recognize because it always take this form: ‘Of course
Mr. X argues this way; just look at the circumstances that affect hi
m.’
Example:
•Haileselassie I of Ethiopia argued in the League of Nations that
member states should give hand to Ethiopia to expel the fascist Ital
y from the country. But the member states should not listen to the k
ing. Haileselassie I argue in this way because he wants to resume
his power once the Italian are expelled from Ethiopia
•Ato Mohammed has just argued to replace the public school syste
m with private school system. But, of course, he argues that way. H
e has no kids, and he does not want to pay any more taxes for publi

iii. tu quoque (you too) fallacy
 Second arguer attempts to make the first appear to be hypocri
tical or arguing in bad faith
 This fallacy has the following form: ‘How dare you argue that
I should stop doing X; why you do (have done) X yourself?’
 So, arguer(2nd ) discredits the argument of an opponent by cla
iming that the idea he advance as false and contrary with wha
t he has said or done before
Example:
• Patient to a Doctor: Look Doctor, you cannot advise me to quit s
moking cigarette because you yourself is a smoker.
• How do you advise me to quit smoking while you yourself are s
moking?
• Child to parent: Your argument that I should stop stealing cand
y from the corner store is no good. just a week ago You told me y
ou, too, stole candy when you were a kid.

5. Accident
Committed when a general rule is applied to a specific case
it was not intended to cover
Example:
oFreedom of speech is a constitutionally guaranteed right. Ther
efore, John Q. Radical should not be arrested for his speech th
at incited riot last week.
oProperty should be returned to its rightful owner. That drunke
n sailor who is starting a fight with his opponents at the pool ta
ble lent you his 45-caliber pistol, and now he wants it back. The
refore, you should return it to him now.

6. Straw Man
 Committed when an arguer distorts an opponent‘s argument for t
he purpose of more easily attacking it.
 main features of straw man fallacy
 First, there are always two individuals discussing about
controversial issues: One(1st arguer) of the arguers presents
his views about the issues and the other(2nd arguer) is a critic
 Second, the 2nd arguer does not rationally criticize the main
argument of the opponent Rather misrepresented ideas of
original argument.
 Third the 2nd person concludes by criticizing the
misrepresented idea
 When the fallacy of straw man occurs readers should keep in
mind two things.
– First, they have to try to identify the original argument, which
is misrepresented by the critic.
– Second, they should look for what gone wrong in the
misrepresentation of the argument.

Example:
•Mr. Belay believes that ethnic federalism has just destroyed the c
ountry and thus it should be replaced by geographical federalism.
But we should not accept his proposal. Geographical federalism
was the kind of state structure during Derg and monarchical regi
me which suppress right of national nationalities and peoples of
Ethiopia.
•Mr. Goldberg has argued against prayer in the public schools. O
bviously, Mr. Gold-berg advocates atheism. But atheism is what t
hey used to have in Russia. Atheism leads to the suppression of al
l religions and the replacement of God by an omnipotent state. Is
that what we want for this country? I hardly think so. Clearly Mr.
Goldberg’s argument is nonsense.

7. Missing the point
Premise of an argument supports a conclusion which is different but vagu
ely related to the correct one (cocnclusion)
If one suspects that such fallacy is committed, he or she should identify the
correct conclusion, the conclusion that the premises logically imply
Arguer is ignorant of the logical implications of his or her own premises a
nd draws a conclusion that misses the point entirely
Examples
•The world is in the process of globalizing more than ever. The world economy is becom
ing more and more interconnected. Multinational companies and supra national institu
tions are taking power from local companies and national governments. The livelihood
of people is randomly affected by action and decision made on the other side of the plan
et and this process benefits only the rich nations at the expense of the poor. What shoul
d be done? The answer is obvious: poor nations should detach themselves from the proc
ess.
•Crimes of theft and robbery have been increasing at an alarming rate lately. The concl
usion is obvious: we must reinstate the death penalty immediately.

8. Red Herring
Arguer diverts the attention of the L/R by changing
the original subject in to totally different issue
Arguer ignores the main topic and shifts the attenti
on of his audiences to another totally different issue
Draws conclusion from the changed issue
Arguer mislead L/R using two different technique
s
change the subject to one that is subtly related to
the original subject
change the subject to some flashy, eye-catching
topic that distract the attention of the L/R

Example:
 Environmentalists are continually harping about t
he dangers of nuclear power. Unfortunately, electri
city is dangerous no matter where it comes from. E
very year hundreds of people are electrocuted by ac
cident. Since most of these accidents are caused by
carelessness, they could be avoided if people would
just exercise greater caution.
 There is a good deal of talk these days about the ne
ed to eliminate pesticides from our fruits and veget
ables. But many of these foods are essential to our
health. Carrots are an excellent source of vitamin
A, broccoli is rich in iron, and oranges and grapefr
uits have lots of vitamin C.

To differentiate SM,RH & MP fallacies ……..
1. both red herring and straw man proceed by
generating a new set of premises
- but Missing the point draws a conclusion from the
original premises
2. In both red herring and straw man, the
conclusion is relevant to the premises from which
it’s drawn
- But in missing the point, the conclusion is
irrelevant to the premises from which it’s drawn

2. Fallacies of Weak Induction
 Occurred due to weak connection between the P&C
Premises is relevant to the C but doesn’t contains suffi
cient evidence
Includes six fallacies :
 Appeal to unqualified authority
C cites statement of others
 Appeal to ignorance
lack of proof definitely supports a conclusion
 Hasty generalization
 C depends on insufficient info. and
unrepresentative sample

 Fallacy of Weak Analogy
 C depends on insignificant similarity
two events
 Slippery Slope fallacy
C depends on alleged chain reaction
with less probability to happen in
reality
 False Cause fallacy
C depends on imagined causal
connection which may not happen in
reality

9. Appeal to unqualified authority
 Arguer draws conclusion by citing the idea of unq
ualified authority whose idea is untrustworthy .
 A person is unqualified authority when he/she:
 lacks the expertise/Profession
 make biased or prejudiced judgment
 Has the motive to lie or
 Has the motive to disseminate “misinformation
”
 lacks the ability to perceive or recall things

Example:
A. Dr. Bradshaw, our family physician, has stated that
the creation of muonic atoms of deuterium and tritium
hold the key to producing a sustained nuclear fusion r
eaction at room temperature. In view of Dr. Bradshaw’
s expertise as a physician, we must conclude that this i
s indeed true.
B. David Duke, former Grand Wizard of the Ku Klux
Klan, has stated, ‘‘Jews are not good Americans. They
have no understanding of what America is.’’ On the ba
sis of Duke’s authority, we must therefore conclude th
at the Jews in this country are un-American

C. Old Mrs. Ferguson (who is practically blind) has test
ified that she saw the defendant stab the victim with a
bayonet while she was standing in the twilight shado
ws 100 yards from the incident. Therefore, members
of the jury, you must find the defendant guilty
D. James W. Johnston, Chairman of R. J. Reynolds Tob
acco Company, testified before Congress that tobacco
is not an addictive substance and that smoking cigare
ttes does not produce any addiction. Therefore, we sh
ould believe him and conclude that smoking does not
in fact lead to any addiction.

10. Appeal to Ignorance
Committed when one’s ignorance, lack of evidence and
Lack of knowledge definitely supports the conclusion
premises state that nothing has been proved about som
ething but the conclusion makes a definite assertion abo
ut that thing.
Committed when Someone argues that:
 Something(X) is true because no one has proved it
to be false or
 Something(X) is false because no one has proved it
to be true
 Group of people have been conducted research for
decades to check the existence of ‘X’ but all failed t

Examples:
a.Nobody has ever proved the existence of UFO. Therefore, U
FO doesn’t exist.
b.People have been trying for centuries to disprove the claims
of astrology, and no one has ever succeeded. Therefore, we
must conclude that the claim of astrology is true.
Exceptions
1. If group of experts/scientist investigate something in their
own area of expertise and found nothing
example :
Teams of scientists attempted over a number of decades to
detect the existence of the UFO and all failed to do so.
Therefore, UFO does not exist.

2. Legal [court room] procedure
example :
 Members of the jury, you have heard the prosecution
present its case against the defendant. Nothing,
however, has been proved beyond a reasonable
doubt. Therefore, under the law, the defendant is not
guilty.
3. There are also cases where mere see and reporting
are enough or sufficient to prove something which
needs no expertise
example :
 No one has ever seen Mr. Andrews drink a glass of
wine, beer, or any other alcoholic beverage. Probably
Mr. Andrews is a nondrinker.

11. Hasty Generalization
Arguer draws conclusion based on insufficient information and
unrepresentative sample or occurs when there is a reasonable
likelihood that the sample is not representative of the group
Sample non representative when
 sample is too small or
 sample [large but] not selected randomly
Committed by individuals who develop a negative attitude or
prejudice towards others
Example:
Six Arab fundamentalists were convicted of bombing the World
Trade Center in New York City. The message is clear: Arabs are
nothing but a pack of religious fanatics prone to violence.

12. False Cause fallacy
Conclusion depends on some imagined
causal connection of events which may not
exist in reality
Depends on ‘X’ causes ‘Y’ while ‘X’ may
not probably cause ‘Y’ to happen at all
Three varieties of false cause fallacy
 Post hoc ergo propter hoc
 Non Causa pro Causa
 Oversimplified Cause

 Post hoc ergo propter hoc fallacy
Means After this, on account of this
Depends on temporal succession of events
 ‘Y’ is caused by ‘X’, because ‘X’ exist before ‘y’
Example
• During the past two months, every time that the cheerleaders
have worn blue ribbons in their hair, the basketball team has
been defeated. Therefore, to prevent defeats in the future, the
cheerleaders should get rid of those blue ribbons.
occurs in cultural superstition -associate with bad luck
Example
• ‘‘A black cat crossed my path and later I tripped and sprained
my ankle. It must be that black cats really are bad luck.’’

 Non Causa pro Causa Fallacy
Means ‘Not the cause for the cause’
Occurred when conclusion depends on either
 coincidental occurrence of events or
 Mistake cause for an effect
Examples
• There are more churches in Ethiopia today than ever
before and more HIV victims ever before; so, to eliminate
the epidemic we must abolish the church.
• Successful business executives are paid salaries in excess
of $50,000. Therefore, the best way to ensure that
Ferguson will become a successful executive is to raise
his salary to at least $50,000.

Oversimplified Cause Fallacy
Multitude of causes are responsible
for a certain effect but the arguer
selects just one of these causes and
represents it as the sole cause
Example
o The quality of education in our grade
schools and high schools has been
declining for years. Clearly, our
teachers just aren’t doing their job
these days.

13. Slippery Slope fallacy
a variety of false cause fallacies
event ‘X’ is the cause of event ‘Y’….. but it
takes place in a series of events or actions
Conclusion of an argument rests upon an
alleged chain reaction but not sufficient to
think that the chain reaction will actually
happen
The first event is taken as cause fall all the
event to happen in a series

Example:
A. Against cultural, social and religious norms of Ethiopia, a
Chinese firm was authorized to run donkey slaughter hou
se in Bishoftu. But this company should be closed. If donk
eys are continuously slaughtered and exported, then Ethio
pian who works in the abattoir will start to eat donkey me
at. Then members of the family of these workers will be t
he next to eat donkey meat. This gradually leads their nei
ghbors and the village to accept the same practice. Finally
, the whole country will follow which in turn leads to the t
otal collapse of Ethiopian food culture.

• B. Immediate steps should be taken to outlaw
pornography once and for all. The continued
manufacture and sale of pornographic
material will almost certainly lead to an
increase in sex-related crimes such as rape
and incest. This in turn will gradually erode
the moral fabric of society and result in an
increase in crimes of all sorts. Eventually a
complete disintegration of law and order will
occur, leading in the end to the total collapse

14. Fallacy of Weak Analogy
arguer draws conclusion depending on insignificant similariti
es of two or more things
The similarity between two things is not strong enough to s
upport the conclusion
The basic structure of the fallacy
» Entity A has attributes a, b, c and z
» Entity B has attributes a, b, c
» Therefore, entity B probably has attribute z.
Example:
Harper’s new car is bright blue, has leather upholstery, and get
s excellent gas mile age. Crowley’s new car is also bright blue a
nd has leather upholstery. Therefore, it probably gets excellent
gas mileage, too.

3.3 Fallacies of Presumption
To presume means to take something for granted or
to assume a given idea as true (while in fact not true)
The assumption given in the premise is not supported
by proof but arguer invite the audiences to accept as it i
s.
Arguer uses confusing expressions-to conceal the wron
g assumption
Contains fallacies of:
Begging the question
Complex question
False dichotomy
Suppressed evidence

15. Begging the Question
Arguer uses confusing phraseology
Presumes that the premises provide adequate support for
the conclusion
Arguer creates the illusion by stating the inadequate
evidence as adequate to the conclusion by
 Leaving out a key premise- nothing more is needed to
establish the conclusion
Restating the premise as a conclusion - using different
words
Reasoning in a circle- not clear where it begins &ends
 Chxs: Has a valid form
 Contains phraseology that conceal faulty reasoning
The actual source of support for the conclusion is not
apparent

 Leaving out a key premise
Example: Murder is morally wrong. This being the case, it
follows that abortion is morally wrong
 Restating the Premise as a Conclusion
Example: Capital punishment is justified for the crimes of
murder and kidnapping because it is quite legitimate an
d appropriate that someone be put to death for having c
ommitted such hateful and inhuman acts.
 Reasoning in a circle.
 Ford Motor Company clearly produces the finest cars in th
e United States. We know they produce the finest cars beca
use they have the best design engineers. This is true because
they can afford to pay them more than other manufacturer
s. Obviously they can afford to pay them more because they
produce the finest cars in the United States.

16. Complex Question
Arguer asks a single question (that is really two o
r more) and a single answer is then applied to both
question
Oblige the L/R to acknowledge about something
that he or she doesn't want to acknowledge
Example:
- Have you stopped cheating on exams?
•You were asked whether you have stopped cheatin
g on exams. You answered ‘‘yes.’’ Therefore, it follo
ws that you have cheated in the past.

17. False Dichotomy
Premise of an argument presents two alternatives as
if they are jointly exhaustive
the arguer attempt to delude the reader or listener
into thinking that there is no third alternative
Examples:
•Either you buy only Ethiopian-made products or you
don’t deserve to be called a loyal Ethiopian.
Yesterday you bought new Chinese jeans.
Therefore, you don’t deserve to be called a loyal Eth
iopian

18. Suppressed Evidence
Arguer draws conclusion by ignoring the key premise that
outweighs the conclusion
It works by creating the presumption that the premises are
both true and complete when in fact they are not
Common in advertisements/ads/
Example:
•The new RCA Digital Satellite System delivers sharp TV recepti
on from an 18-inch dish antenna, and it costs only $199. Theref
ore, if we buy it, we can enjoy all the channels for a relatively sm
all one-time investment.
•Certainly Danawit will be a capable and the right person for stu
dent president of Arsi university. She has a gorgeous face, and pos
tures and she dresses very fashionably.

3.4 Fallacies of Ambiguity
 Conclusion of an argument depends on either
 a shift in meaning of an ambiguous word or
 wrong interpretation of an ambiguous statement
19. Equivocation
 Conclusion depends on meaning of word which is used i
n two different senses
Examples:
o Some triangles are obtuse. Whatever is obtuse is ignora
nt. Therefore, some triangles are ignorant.
o Any law can be repealed by the legislative authority. But
the law of gravity is a law. Therefore, the law of gravity c
an be repealed by the legislative authority.

20. Amphiboly
Arguer draw a conclusion depending on misinterpreted s
tatement
The original statement- asserted by someone
ambiguity usually arises from :
 a mistake in grammar , punctuation—a missing com
ma, a dangling modifier
 an ambiguous antecedent of a pronoun etc.
So the statement may be understood in two clearly disting
uishable ways.
examples:
oJohn told Henry that he had made a mistake. It follows
John has at least the courage to admit his own mistakes.
 Ambiguous antecedent; it can refer either to John or to Hen
ry. Perhaps John told Henry that Henry had made a mistak

 Difference between Amphiboly & equivocation
 Equivocation – due to ambiguity in meaning of words but
 Amphiboly – due to ambiguity in a statement
--------------------------------------------------------------------------
 Equivocation –involves a mistake made by the
arguer when he constructs an argument
 Amphiboly – involves mistake made by the arguer
in interpreting an ambiguous statement made by
someone else

3.5 Fallacies of Grammatical Analogy
are grammatically similar to other arguments that
are good in every respect
It include fallacies of
21. Composition
conclusion depends on the erroneous transference
of attribute from parts to whole
Examples:
•Each atom in this piece of chalk is invisible. Therefor
e, the chalk is invisible.
•Sodium and chlorine, the atomic components of salt,
are both deadly poisons. Therefore, salt is a deadly poi

22. Division
Conclusion depends on the erroneous transference of attrib
ute from whole to part
An illegitimate transference of attribute from whole to part
Examples:
•Salt is a nonpoisonous compound. Therefore, its component el
ements, sodium and chlorine are nonpoisonous.
But when the transference of attribute from the whole to pa
rt is legitimate , it doesn’t commit fallacy
Example:
•This piece of chalk has a mass. Therefore, the atoms of this p
iece of chalk has mass as well

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