Edo University, Iyamho

Department of Mass Communication

COURSE CODE: JILL 111

COURSE TITLE: Introduction to Logic

LEVEL: 100

COURSE LECTURER: Rev. Fr. Dr. Peter Egielewa

COURSE DESCRIPTION:

This course provides a survey of the main branches of Philosophy, Symbolic Logic Special

symbols in symbolic Logic-conjunction, negation, affirmation, disjunction, equivalent and

conditional statements law of tort, methods of deduction using rules of inference and bi-

conditionals qualification theory, types of discourse, nature of arguments, validity and

soundness, techniques for evaluating arguments, distinction between inductive and deductive

inferences. Illustrations will be taken from familiar texts, Including literature materials,

Novels, Law reports and newspaper publications.

COURSE CONTENT/OUTLINE

Weeks Subject Content

1 & 2 Meaning and Nature of Logic

3 The Vocabulary of Logic

4 & 5 Arguments and Types

6 Truth and Validity

7 Uses of Language

8 & 9 Fallacies

10 & 11 Definitions

12 Revision

Week 1 & 2 Meaning and Nature of Logic

Week 3 The Vocabulary of Logic

Week 4 & 5 Arguments and Types

Week 6 Truth and Validity

Week 7 Uses of Language

Week 8 Fallacies I

Week 9 Fallacies II

Week 10 Definitions I

Week 11 Definitions II

COURSE ASSESSMENT MARKING SCHEME

Assessment Marks

Written test 30 marks

End of semester examination 70 marks

Total 100%

Attendance compulsory 75% to enable candidate seat for exams

FIRST SEMESTER COURSE SCHEDULE

1stsemes

ter

(12

weeks)

Dat

e

Topic Lesson content Resources Assessm

ent

Week 1 Meaning

and

nature of

Logic

Definition of Logic, origin of

Logic, Classification of logic

Textbooks/Multi-

media

Question

and

answer

with all

students

Week 2 Meaning

and

nature of

Logic

Definition of Logic, origin of

Logic, Classification of logic

Textbooks/Multi-

media

Question

and

answer

with all

students

Week 3 The

Vocabul

ary of

Logic

Objective, Statement, Premise,

Inference, Conclusion,

Summary, Conclusion

Textbooks/Multi-

media

Question

and

answer

with all

students

Week 4 Argumen

ts, types

Definition of Argument,

Inductive and Deductive

Arguments, Valid & Invalid

Arguments, Sound and

Unsound Arguments

Textbooks/Multi-

media

Question

and

answer

with all

students

Week 5 Argumen

ts, types

Definition of Argument,

Inductive and Deductive

Arguments, Valid & Invalid

Textbooks/Multi-

media

Question

and

answer

Arguments, Sound and

Unsound Arguments

with all

students

Week 6 Truth

and

validity

a)What are arguments, b)what

must be present for a discourse

or assertion to be called an

argument

c) Rules of argumentative

discourse

d) Premises as important pieces

of argument

e) Premises and conclusion in

argument

f) Conditional statements and

bi-conditional statements, if and

only if

g)Validity and soundness of

arguments, weak and strong

arguments

Textbooks/Multi-

media

Question

and

answer

with all

students

Week 7 Uses of

language

i) Functions of

language

ii) Models of

Linguistic

Analysis

(Chomsk’s

Structural

Analysis, J.I.

ustin,

M.A.K.

Halliday)

Textbooks/Multi-

media

Question

and

answer

with all

students

Week 8 Fallacies

I

Definition and Classification of

fallacies,

Textbooks/Multi-

media

Question

and

answer

with all

students

Week 9 Fallacies

II

Fallacies of Ambiguity,

Equivocation, Amphiboly,

Division, Unwarranted

Assumptions, begging the

Question, False Dilemma,

fallacy of false Cause, Appeals

of False Authority, Complex

Question

Textbooks/Multi-

media

Question

and

answer

with all

students

Week 10 Definitio

ns I

Major types of Definitions Textbooks/Multi-

media

Question

and

answer

with all

students

Week 11 Definitio

ns II

Stipulative Definition, Real

definition, definitions by Genus

and Difference.

Textbooks/Multi

media

Question

and

answer

with all

students

Week 12 All

course

contents

Revision Lecture note Question

and

answer

with all

students

Recommended literature

Hausman, Alan et al (2013), logic and Philosophy: A Modern Introduction, USA, Wadsworth

Cengage Learning.

Maduka, Chukwugozie (1996), Philosophy and Logic: A First Course, Iliad Publishers.

Ujomu, P. et al (2011), Philosophy and Logic: An Introduction, Benin City, University of

Benin Publication.

1. General Introduction and setting the tone, Defining Philosophy and Etymology.

1.1 What is Logic?

Logic has a definition that is generally agreed upon. This is not the case with other disciplines

such as philosophy. From its etymology, Logic is from the Greek word “Logos” meaning

“word, discourse, study. There are different scholars who have defined Logic thus

“Study of the methods and principles used in distinguishing good (correct from bad (incorrect

reasoning)” (Copi, 1968). It is the science of the discovering correct or incorrect reasoning.

Logic can also mean the study of the evaluation of arguments. Infact, the trains of logic is

referred to Arguments or arguments schemata. Logic involves analyzing concepts using

rigorous critical and analytical tools to discover reasoning that can be judged or weak. To be

logical, certain laws and principles must be adhered to. It is principally the study of arguments

in order to be able to determine good from bad arguments. Logic forms the foundation of

logical thought. Thus, it is the business of logic to find out what makes an argument valid.

The components of such logical thought come from various facts which come from personal

experience, recorded experience of others and the ability to reason. Such facts which can be

erroneous are then subjected to critical evaluation through the process of identification,

interpretation and analysis. Because of the possibility of error, all logical processes must be

carefully and thoroughly examined without hast.

1.2. Origin of Logic

Logic can be traced back to Aristotle more than 2000 years ago. He assembled and arranged a

philosophical what is known as “syllogistic logic” or syllogism. Syllogism is a kind of

inference in which a conclusion is drawn from two premises e.g

P1 All men are mortal.

P2 Peter is a man.dis

-------------------------

C Peter is Mortal.

And

P1 All children are selfish.

P2 Some people are not selfish.

……………………………………………

C Some people are not children.

The following syllogisms of Aristotle.

All A are B (Universal Affirmative)

All A are not-B (Universal Negative)

Some A are B (Particular Affirmative)

Some A are not-B (Particular Negative)

1.3 Subject matter of Logic

Logic is not interested in our thoughts. Logic is interested more in expressed thoughts

verbally or in writing. Thought in the context is not the process. In the process of thinking,

logic is very useful in helping your formulate your thought pattern and arrange your ideas to

make sense. But the product of one’s thought process is the main subject of logic. Once the

thought process is completed, logic comes in to evaluate the thought process using logical

principles and rules. In other words, logic is concerned about

1. Your conclusion, position, recommendation

2. Your evidence and reasons adduced for reaching certain conclusions

3. Interested in the connection between your conclusion, recommendation and the

premises, basis or evidences for them

Logic is not concerned about thought processes that do not have conclusion and evidence

from them. This is called reasoning. Thus, all reasonings are products of thinking. But not all

thinking are reasoning. When you are reasoning on an issue in such as way to arrive at a

conclusion, you are thinking and doing logic but if your thinking does jot end with the reason-

evidence template, you are just think.

An Example:

The banana I bought yesterday is spoilt and thank God that you did not eat it=That is thinking

and religion at play, not logic.

But when you say:

The banana I bought yesterday is spoilt. Therefore, I will return it and demand for refund,

then you are doing logic.

P1 The banana I bought yesterday is spoilt.

……………………………………………………………………….

C I will return it and ask for a refund.

As Onyeocha I.M puts it, “what logic requires is that thought think about thought”. So, logic

studies thought which is the end product of thinking.

1.4 Logical Processes

There are three logical processes: Simple Apprehension, judgement, Reasoning and

Argument.

1.4.1 Simple Apprehension.

This is the process by which the mind perceives something without necessarily passing any

judgment. It is the act of intellectually perceiving an object without affirming or denying it. It

is recognizing an object only for its sake.1 Since the mind cannot physically bring an object to

itself, it can nonetheless intellectually capture such as object in what can be called “species of

the object”. This act of forming such a mental image of an object is called “conception”. This

process of conception derives from the original object, concept, idea, or notion.

An Example:

That is a boy. This is a simple apprehension because I have not denied or affirmed the object

of a boy.

1.4.2 Judgement

Judgement is the act by which a mind affirms or denies something about something. If we

take the example above, it can be reformulated thus: that is a fat boy. By adding “fat”, a

judgment has been passed on the object.

1.4.3 Reasoning and Argument

This is the final phase of the logic process. It is the process through which different kinds of

judgments arrive at a conclusion or other judgments in a process that is called reasoning.

Using the last example, we could say

That is fat boy because he is should be weighing approximately 100Kg.

1.5 Classification of Logic

There are two main classification of Logic: formal and Informal Logic

1.5.1 Formal Logic

Formal Logic, otherwise called Aristotelian Logic or Traditional Logic is the form of logic

that follows logical rules and that are straightforward and clear. Some authors refer to them as

logic that are also deductive in nature. It is the main domain of logic and has a set out

1 https://www3.nd.edu/~maritain/jmc/etext/lamp01.htm. Accessed on 08.12.2017

methodology. It includes simple apprehension (definition), judgement (proposition) and

reasoning (syllogism).

An example is:

P1 Everyone living in Iyamho lives in Etsako West LGA.

P2 Everyone living in Etsako West LGA lives in Edo State.

……………………………………………………………………………….

C Therefore, everyone living in Iyamho lives in Edo State.

1.5.2 Informal Logic

Informal logic, otherwise called material logic is also called inductive logic because it is

usually based on informal, inductive logic that goes from statements of evidence (premises) to

a conclusion that generalizes the evidence. It is informal because it does not follow a set of

rules and the arguments are usually not neatly presented. It reflects on the meanings of words,

concepts, propositions.

An Example:

Some people in Edo State are not famous. However, because I live in Edo State, I ride around

Iyamho in limos and hang out with celebrities. Therefore, I am famous by association.

1.6 Why Study Logic

Logic is studied for various reasons. The importance of Logic is captured in the popular

stamen of As Abraham Lincoln, namely; “you can fool some of the people all of the time, and

all of the people some of the time, but you cannot fool all of the people all of the time.” Logic

is found also in Will Rogers Statement: “A King can stand people fighting, but he can't last

long if people start thinking.” Thus, some of the reasons why people study logic include;

1. It lays down rules for critical reasoning.

2. Teaches one how to formulate sound arguments.

3. Equips one with the skills necessary for presentation of one’s position in an order

manner.

4. Logic will make you a convincing debater, able to detect errors in others and avoid

similar pitfalls.

5. Logic would streamline your life by helping you decide which things are important and

which are not.

6. Logic will reduce the chances of you being manipulated by those who want to control

your thinking and conscience.

7. The logic will reduce the stress

8. Logic helps one to see and discover the interrelationship in the different sciences.

Source: http://fashionmind.eu/fashion-season-2015-2016/10-reasons-for-studying-logic.html

1.7 Logic and other Disciplines

Because almost all disciplines have positions and theories which they always defend, it is

imperative to have the tools for presenting such positions in an error-free context.

1.8 Key Concepts in Logic

To explain Logic, there are basic concepts that help understand logic and its application.

These include: Statements, proposition, arguments, premises, conclusion

1.2.1 Statement: A statement is a declarative sentence or part of a sentence which can be

considered either true or false. In other words, a statement should contain an idea or more

ideas that are subject to critical analysis in order to determine if those set of idea or ideas are

true or false.

2. The Vocabulary of Logic

The vocabulary explains the different terms, concepts that are commonly used in logic in

general and logical discourses in particular. These include: Statement and proposition,

premise, conclusion and inference.

2.1 Statement and Proposition

There is generally no difference between statement and proposition as they are used

interchangeable. However, logicians tend to see a difference between a statement and a

sentence. A statement is a declarative sentence or part of a sentence which can be considered

either true or false. A sentence is a set of words that expresses a statement, a question or

command. In this case only a sentence which expresses an idea or ideas that can be true or

false is a statement and such sentences are called logical statements. A sentence that expresses

command or question is not a statement and therefore is not a logical statement. In other

words, a statement should contain an idea or more ideas that are subject to critical analysis in

order to determine if those set of idea or ideas are true or false.

EXAMPLES: Which of these are statements and which are not?

The Man is tall

Auchi is the capital of Edo State.

Sit down!

Has John resumed?

2.2 Premise

A premise is a statement in an argument that provides reason or support for reaching the

conclusion in that argument. Usually there can be one or several premises in an argument. A

premise can be found at different points of an argument and not necessarily the first statement

or last. But more importantly is that a premise is implied in the conclusion.

An Example:

All Men are mortal

John is a man

Therefore John is mortal

Rewritten, it reads thus;

All Men are mortal (premise)

John is a man (premise)

Therefore John is mortal (conclusion)

From the above, one notices that the first two statements are premises while the last is the

conclusion.

2.3 Premise Indicators

Premise indicators are words which indicate or point to the presence of a premise in an

argument. These include; because, since, for, as, for the reason that, in as much as, as

indicated by, in that, may be inferred from, given that, seeing that, owing to. Statements

which follow these indicators are considered to be premises.

Examples:

The University has done its matriculation ceremony because the new students have their

matriculation numbers.

2.4 Conclusion

A conclusion is a statement within an argument that indicates of what the arguer is trying to

convince the reader/listener. It is the proposition arrived at on the strength of the premises

deduced for it. In such argument where the conclusion follows from the premises, it is called

valid argument. What is the argument he is trying to prove? There is usually only

one conclusion in a single argument.

All 100 Level students of Edo University take the GST 112 course.

Lucy is a 100 level student.

Lucy is taking the GST 112 course.

The Last premise, which is the conclusion, is arrived at on the basis of the first two premises.

In examining premises and conclusion, the task of the reader or listener is to ask what the

author of the argument is trying to get you to believe. The answer to this question is

the conclusion.

There must also be at least one reason and possibly many why the author wants you to believe

what he is saying. These are your premises.

2.5 Conclusion Indicators

These are words which point to a conclusion in an argument. When a statement follows such

an indicator, such a statement is likely to be a conclusion. Such indicators may include:

Therefore, wherefore, accordingly, it must be that, for this reason, entails that, it implies that,

as a result, consequently, hence, we may infer, we may conclude, thus, so, it follows that.

Examples:

Suspected Fulani herdsmen are guilty of extreme human rights abuses. Further, they kill

people unprovoked. Thus, the FG should declare them terrorists.

Students who do sports perform better in school. Hence, students should be encouraged to do

sports.

2.6 Inference

This is the process through which a conclusion is derived from premises.

In the example,

All 100 Level students of Edo University take the GST 112 course

Lucy is a 100 level student

Lucy is taking the GST 112 course.

The process of arriving at “Lucy is taking the GST 112 course” is called an inference.

ASSIGNMENT:

Rewrite the following arguments listing the premise(s) first and the conclusion last. Each line

should be a single statement written as a complete sentence. Label the premise(s) P¹, P², P³,

etc. and the conclusion C. Also write our any premise or conclusion indicators you find and

label them as such.

1. Since students are hardworking. Parents should increase their monthly pocket money.

2. We may infer that the Nigerian Army is good from the results of the Persian Gulf War.

3. Junior is two years old. Most two year olds can walk. It follows that Junior can walk.

4. Because Ibrahim spends is commended by most customers in the bank. He deserves an

award.

Auguments and Types

An argument is a series of statements, one of which is the conclusion (the thing argued for)

and the others are the premises (reasons for accepting the conclusion). (Alan

Hausman, 2007)

An arugument is a group of propositions, one of which is called the conclusion, is affirmed on

the basis of the others, which are called the premises.(Kouassi, 2014).

An argument is the smallest unit of argumentation. There are atleast two statements or

propositions that make up an argument, one of which must be premise and the other

conclusion. But it is important to note that not all statements are arguments. Arguments can be

grouped into broad groups: those, whose premises support the conclusion and those whose

premises do not support the conclusion even if they claim to do so. The first group can be

called good arguments while the seconds are bad arguments. The tasks of logicians is to find

techniques to formlate and use good arguments.

Arguments are a group of statements. Statements are declarative sentences that can either be

true or false.

It is not necessary that the premises provide true reason, neither is it important that premises

actually support the conclusion. What is important is that the premises must claim to present

evidence or reason and there must be a claim that the edivence or reason support.

So it is not sufficient that because a sentence expresses a statement it is an argument, the

statements must be related to one another in appropriate way. Explanations, exposition do not

offer reason that make a concluson to be accepted.

Examine the following and determine which is an argument and which are not and why.

1. I believe in God because that is how I was raised (This is biography. The because is

explanatory, explaining one’s belief in God?

2. I believe in God because life has meaning. If there is no God, Life would be

meaningless. (This is an argument. )

Life has meaning

If there is no God, life would be meaningless

God exists

3. John was afraid of making a commitment to marry. There Agnes was not surprise that

broken up. (This is explantory, explaining why Agness was not surprised of the break

up)

4. We will get a tax break if we marry before the end of the year. Therefore, I think we

should move our wedding date up and not waitign until January. (This is an argument)

We will get a tax break if we marry before the end of the year.

Therefore, we should move our wedding date up and not waitign until January.

Deduductive and Inductive arguments

Deductive Argument

A deductive argument is an argument in which the arguer claims that the conclusion cannot be

false if the premises are true. In such a case, the conclusion is said to follow necessarily from

the premises. So deductive arguments are those that involve necessary reasoning.

Example:

All dogs are carnivores

Poppy is a dog

Therefore, Poppy is a carnivore

Inductive Argument

An inductive argument is an argument in which the arguer claims that it is improbable that the

conclusion is false when the premises are true, that is the conclusion is calimed to follow only

prpbably from the premises. Inductive arguments are those that involve probabbilistic

reasoning due to the use of such words as improbble, plausible, implausible, likely, unlikely.

Example:

The Dog is closely related to the tiger

The tiger thrives on rabbits

Therefore, the dog prpbably thrives on rabbits.

The main difference between the deductive and inductive argument is the strength of the

argument’s inferential claim, that is how strong the conclusion is claimed to follow from the

premises.

Since the strength of the inferential claim is sometimes difficult to know, one must employ

one’s interpretative abilities to make this distinction. However, there are certain criteria that

should be met in order to arrive at such judgement:

(1) The occurrence of the special ´indicator words (2) the actual strength of the inferantial

link btween premises and conclusion (3) the form or style of argumentation used by

the arguer.

Deductive argument Forms:

Many Arguments have unique character that indicate that the premises are supposed to give

absolute support to the conclusion.Five of such shall be examined:

1. Arguments based on mathematics: These are deductive arguments in which the

conclusion are based on some mathematical computation or geometry. These

arguments are deductive because the premises provide absolutete support for the

conclusions.

Example:

There are 2 shoes in my bag

There are 3 sandals in my bag

Therefore, there are 5 footwears in my bag.

2. Arguments based on definition: This is an argument in which the conclusion is

based on the definition of certain words or phrases used in the premises. These

arguments are deductive because the concluion follows necessarily from the

conclusion.

Examples:

Because Joseph is a genius, it follows that Joseph has a peculiar, distinctive, or identifying

character.

Since Agatha is an undergraduate, therefore she is a student at university who has not

received her bachelor's degree.

3. Categorical Syllogism. A syllogism is an argument made up exactly of two premises

and a conclusion. A categorical syllogism is a type of syllogism in which each

statement begins with the words “all”, “no” or “some”.

Example:

All EUI students are innovative students

Some EUI students are hard working

Some innovative students are hard working

4. Hypothetical Syllogism

A hypothetical syllogism is one that has a conditional statement in one or both of its

premises.

Examples:

If petrol prices continue to increase, people will lose their jobs

If people lose their jobs, the country will be unstable

Therefore, if petrol prices continue to increase, the country will be unstable

If NTA airs only the ruling party view during political campaigns, then opposition

parties will use other media outlets during campaigns.

NTA airs only the ruling party view during political campaigns.

Therefore, opposition parties will use other media outlets during campaigns

5. Disjunctive Syllogism:

This is a syllogism that contains disjunctive statements in one of its premises in its

argument, that when it uses such words as “either…..or”.

Examples:

Either Lagos will be the capital of Nigeria, or Abuja will become the capital of Nigeria.

Lagos will not be the capital of Nigeria

Therefore, Abuja will be the capital of Nigeria

Either JILL 111 lectures take place in Campus A or Either JILL 111 lectures take place

in Campus B.

JILL 111 lectures do not take place in Campus B.

Therefore, JILL 111 lectures take place in Campus A.

Inductive Argument Forms

Generally, inductive arguments re those in which the content of the conclusion intend to

go beyond the content of the premises. The content of the typically deal with familiar

content and goes from there to content in the conclusion that are less familiar. Below are

common inductive argument forms:

1. Prediction: This is an argument that begins from the knowledge of the past to make a

claim about the future. But because, no one knows the future with certainty, such

arguments are normally categorised as inductive.

Examples:

Because people loved Buhari in 2015, they voted for him.

People love Goodluck Jonathan now.

They will vote for him in 2019.

Most students ate in the school canteen last year and not in the local restaurant because

their meals were delicious

Most students will eat in the school canteen this year because the meals are delicious.

2. Arguments from Analogy:

This type of argument depends on an analogy or similarity between two things or

states of affairs. This is such that the condition that is considered to affect the better

known thing or condition is concluded to affect the less-known thing or conclusion.

Example:

Serena and Venus Williams are Sisters and they good in Tennis

Because Serena Williams won the 2017 Australian Open Tennis championship, Venus

Williams will win the 2018 Australian Open Tennis championship.

3. Argument from Authority:

This is an argument which claims that somethings is true because someone in

authority or an expert has said it is so.

Example:

Because the IG of Police has said recently that the recent killings in Benue state are

communal clashes, therefore, it was a communal class

4. Argument based on signs:

This is an argument that is based on the knowledge of a sign to a claim about

something or a situation.

Example: Because the road sign says the road is curvy, the road is curvy.

Deductive Arguments

Valid and Invalid Arguments

Valid Arguments

A valid argument is an argument in which it is impossible for the conclusion to be false if the

premises are true. In other words, the conclusion follows necessarily from the premises. Once

the premises are true, the conclusion must necessarily be true as well. There is a connection

between the premises and conclusion. In a valid argument, the truth or falsity of the content of

the statements of the arguments does not really matter as long as the conclusion necessarily

derives from the premises. An argument can be valid even when all the premises are false.

Examples:

All EUI students are hardworking

John is an EUI student

Therefore, John is hard working

All Logic students know Syllogism

Elizabeth is a logic student

Therefore Elizabeth knows logic

Note that an argument can be valid even when one or more of the premises are false. The

most important factor is that if the premises are given as true, the conclusion must necessarily

be true.

Examples:

All men eat pork (False)

James is a man (True)

Therefore, James eats pork (True/False)

All Vegetarians eat only vegetables (True)

Some dogs are vegetarians (False)

Therefore, some dogs are eat only vegetables (False)

There are cases when all premises are true and the conclusion is false. One must not be in hast

to make such conclusions on the basis of the premises.

Example:

Some Nigerians are bad (True)

Ukwa is a Nigeria (True)

Therefore, Ukwa is bad. (May be false)

Invalid Arguments

An invalid argument is an argument in which it is possible for the conclusion to be false when

the premises are true. In this case, the conclusion does not follow necessarily from the

premises.

Example:

All Universities are educational institutions

EUI is an educational instituion

Therefore, EUI is a University

In generally, validity preserves truths of the statements and does not concern itself with

peserving the falsehold of the statements of an argument.

Sound and Unsound Arguments

Sound Arguments

A sound argument is an argument that is valid and all the premises are true. These two

condition are necessary for an argument to be considered sound. If any of the conditions is

missing that argument is unsound.

Example:

All men are mortal

Socrates is a man

Therefore, Socrates is mortal

This argument fulfils both conditions of validity and truth and therefore is a sound argument.

Unsound Arguments

An Unsound argument is an argument that is invalid and has one or more false premises. In an

insound argument, the premise that is false must be needed to support the conclusion. Other

premises that’s are not needed to support the conclusion become superfluous.

Example:

All ducks are mammals.

Dave is a duck.

Therefore, Dave is a mammal.

This argument is valid because if the premises are true then the conclusion would also be true.

But in this case, it does not have true premises. Therefore the argument is valid but unsound.

Inductive Arguments

Strong and Weak Arguments

Strong Arguments

A strong inductive argument is one in which it is improbable that the conclusion be false

given that the premises are true. In other words, it is an argument that succeeds in providing

probable, but not conclusive, logical support for its conclusion.

All dinosaur bones discovered to this day have been atleat 50 million years old

Therefore, probably the next dinosaur bone to be found will be at least 50 million years old.

All rain water tested to this day have contained sugar. Therefore, probably the next rain water

to be tested will contain sugar.

Most Nigerians have grey hair.

Sam is a Nigerian.

Therefore, Sam has grey hair.

Weak Arguments

A weak argument is an inductive argument that fails to provide probable support for its

conclusion. In other words, if the conclusion is unlikely to be true when the premises are true,

then the argument is weak.

Examples:

Most Nigerians have grey hair.

Sam has grey hair.

Therefore, Sam is a Nigerian.

When a lit match stick is dipped in water, the flame is put out

Petrol is liquid, just like water,

Therefore, when a lit match stick is dipped in petrol, the flame is put out.

Nigerian economy has continued to slide in a downward fall.

Therefore, the transport sector will witness increase in traffic.

Weak and strong arguments have to do with the degree of probability. As the probablity

increases, so does the argument become stronger. The likelihood thaat the conclusion istrue

must be more than 50 percent.

Examine these two arguments

1. This bag has 100 oranges

4 selcted oranges were found to be ripe

Therefore, probably all the oranges in the bag are ripe

2. This bag has 100 oranges

82 selected oranges were found to be ripe

Therefore, probably all the oranges in the bag are ripe.

Argument 1 is weak while 2 is strong. But this can change if the selected in 1 becomes

30 and the selected in 2 reduces to 60.

Cogent and Uncogent Arguments

Cogent Arguments

A cogent inductive argument is one that is strong and has all true premises.

Examples:

Patrick was born in North America and Patrick wasn’t born in Mexico. It’s thus quite

probable that Patrick was born in the USA.

(This argument is strong and cogent)

Most recording artists are gifted.

Don Jazzi is a recording artist.

Therefore, Don Jazzi probably is gifted.

(This argument is strong and cogent)

Uncogent Arguments

An Uncogent argument is one which is weak, has one or more false premises or both.

Example:

Most boys like to play sports.

Serena Williams is a boy.

Therefore, Serena Williams likes to play sports.

(strong but uncogent argument)

Uses of Language

The function of language is unlimited. Basically language is used to ask questions, tell stories,

greet someone, form hypotheses, tell jokes, give directions, sing, songs, issue commands,

launch verbal assault.

Definition of Language:

1. Informative Function

This involves an attempt to communicate some information or content. The main goal here is

to give information which may turn out to be true or false. Thus, one says: “My birthday is 4th

February” or “My phone No is 0406329425” or “Edo University is located on Km 7, Abuja-

Okene Express way, Iyamho”, then one is using language informatively.

2. Expressive Function

This kind of function of language is meant to express or evoke some feelings. This use does

not, in general, convey any information, they are still very important in the day to day

communication since feelings constitute a large part of are expressions and reaction to daily

events around us. So if one yells, “ouch!” or “oh yes”.

3. Directive Function

This kind of function is meant to cause a certain action to take place or prevent it from taking

place through a human agent. It involves, asking question, giving a direction, giving a

command. One is using the directive function of language when one says, “open the door” or

“read that book”.

4. Emotive Function

The function is use to propagate feelings or attitudes, for example when one says, “God is

great”.

5. Commissive Function

This occurs when language is used to make a commitment e.g. in vows, promises or

undertakings. An example during wedding ceremony, the couple says to themselves “I

promise to be true to you in good and in bad times”.

6. Performatory or Declarative Function

This denotes an action which takes place when one uses the first person verb to make a

declaration that makes something to happen. For example, I accept or I declare this meeting

closed.

7. Ceremonial Function.

This is also called ritual language use. It involves a mix of expressive, directive and

performatory functions of language in ceremonies especially religious ceremonies. E.g. “

Dear beloved brothers and sisters, we are gathered here to witness the marriage ceremony

between Lucy and John.

Some Models of Linguistic Analysis

1. Chomsky Structural Analysis of the Universals of Syntax

In the 1960s Noam Chomski proposed that the grammar of a language is a natural competence

of the native speakers of that language. For him, all humans are born with an innate

knowledge or competence that serves as the basis of all language acquisition. Such

grammatical competence is defined as the native speakers’ tacit knowledge of the grammar of

their language (Chomsky, 1965). Thus, native speakers acquire this competence by their

intuitions about grammaticality of sentences generated in their own language. A Universal

Grammar is not necessarily tied to any individual language like Igbo, Yoruba or Hausa

but is a set of hypotheses of the nature of possible and impossible grammars of human

languages. When this happens then such a language is descriptive because it describes

the properties of the intended language following the principles of Universal grammar

or syntax. Chomsky argues that while language is innate and leaned, it is the innate

dimension that makes it possible in the first place to learn it. It describes this as LAD

(Language Acquisition Device). LAD is the device present in every infant, the mental

capacity that enables people to acquire and use language. This capacity is inborn in

humans. At infancy it is shown in sounds but later on it follows a linguistic form that

language represents.

Language, according to Chomsky is governed certain number of rules and principles of syntax which determine the order of words and sentences. It is such innate rules that help one to understand language sentence even when we are unaware of them. Everyone says: “that’s how you say it” and not “how that’s you it say” and that the words “John” and “him” cannot mean the same person in the sentence “John loves him.” But refer to the same person in “John knows that his father loves him.”

2. J. L. Austin Speech Acts

In 1962, in his work “How to do things with words”, claims that speech acts not only

describes a situation or states some facts, but also performs a certain kind of action by itself.

Austin a speech can be categorized as a “performative sentence” or “performative utterance”

based on the function that speech elicits. Our choice of utterance helps to fulfil what function

that language is performing at the time. Language carries with it intentions of the speaker

revealed by the choice of our utterances. The sentence, “You have a wonderful smile” can

function of praise, telling irony, begging for money depending on contexts.

3. M.A.K Halliday Language function

Proposes some funtions of language and that language serves some extra-linguistic role. There

are seven of such functions which include:

i. Instrumental: Language serves in this context to obtain goods and service or to

express a need. E.g. I want ice cream.

ii. Regulatory Function: To control the behaviour of others. E g. sit down

iii. Interactional: To interract or relate with others. E.g you and I will go to the stream.

iv. Personal: This functions takes place when we try to express ourselves, our unique

state or feelings.

v. Heuristic Function: This takes place when one tries to explore and gain knowledge

of the immediate environment. E.g. What is that?

vi. Imaginative Function: This is when language is used to create an imaginary

situation, tell jokes or stories. E.g lets pretend…………..

vii. Informative Function: This function of language happens when one tries to

convery facts or information. It is about something is not known. E.g. “He is coming

at 2:00pm.”

Fallacies

A fallacy is from the latin word “falor” meaning “to be deceived”. A fallacy tends to deceived

one to accept the veracity of a claim or arugment, when the claims is not etablishe din th

arugment. Thus, a Fallacy is a defect in an argument that consists in something rather than

merely false premises. In other words, fallacy is a mistake in reasoning which can make a bad

argument appear good. Such an argument that involves a mistake in reasoning is somethimes

called “non sequitur” (Latin) which means “it does not follow”. Fallacies do not provide

justifiable reasons for the conclusions they are meant to support.

In trying to get people to believe in their positions, tricks, sentiments and emotions are often

employed. A fallacy identifies the errors in a reasoning. According to Copi, a fallacy is “an

argument that may seem to be correct but which proves upon examination not to be so”.

People tend to accept fallacies because of the emotional or psychological dimensions which

make them look like good argument but in reality, a fallacy is bad reasoning howesover it

appears. It is an arror in reasoning.

There are certain factos that can lead to erroneous arguments or fallcy. These include;

Commission, omission carelessness, passion about things in general, unexamined religious

sentiments,

Classes of Fallacies

Fallacies can be classified into two: Formal and Informal fallacies

Formal fallacies

These are fallacies that are those that are identified by merely examining the form or strcuture

of an argument. Such types of fallacie are found only in deductive arguments. They have

nothing to do with the subject matte of the argument but more on the form of the arugment.

Examples:

All bullfights are grotesque ritual

All executions are grotesque ritual

Therefore, all bullfights are executions

It takes the form

All A are B

All C are B

…………………….

All A are C

Problem is wih the 2nd premise. It does not offer any support

To the conclusion.

If apes are intelligent, then apes can solves puzzles

Apes can solve puzzles.

Therfore, Apes are intelligent

It has the form:

If A then B

B.

----------------

A

Informal fallacies

These are auguments that can be detected only by examining the content of the argument.

To detect this fallacy, one must know somehting about the content of the argument.

Example:

The Brooklyn bridge is made up of atoms

Atoms are invisible

……………………………..

The Brookly bridge is invisible

Note: The Brooklyn Bridge may be made up of atoms but it is not invisible.

An athlete is a person

A bad athlete is a bad person.

Note: bad must be defined. A bad athlete does not make a person bad.

Informal fallacies can be grouped into 5, namely

1. Fallacies of Relevance

2. Fallacies of Weak Induction

3. Fallacies of Presumption

4. Fallacies of Ambiguity

5. Fallacies of Gramatical Analogy

1. Fallacies of Relevance

This fallacy occurs when the arguments in which they occur have premises that logically

irrelevant to the conclusion. The premises may seem to support the conclusion, but they do

not. The premises in this kind of argument only provide emotional justification for its

conclusion and not logical premises.

a. Argumentum ad Baculum (Appeal to the “stick”)/Appeal to Force

This type of fallacy occurs when an arguer compels another person to accept a conclusion

by implicitly or explitely threatening the person with the use of focrce. It involves the use

of threat to get someone to take the arguer’s position. It could be a potential use of force

or it could be a psychological threat. In such arguments, such use of focre is completely

irelevant to the argument. It may be directed at a single individul or group of persons.

Examples:

I need some money from you, I will let your parents know you were not in school for a week.

Snakes swallow money in Nigeria. Say yes or I slap you.

2. Argumentum ad Misericordiam (Appeal to pity)

This fallacy occurs when the arguer appeals to pity from of the listener or reader or even a

third party. This appeal to pity is not logically relevant to the conclusion but may evoke the

sense of pity of the listerner to accept the argument of the arguer. The aim of the arguer

therefore, is to get the listener to accept the position of thr arguer.

Example.

Defendant accused of murdering his wife to Judge: Sir I am not guilty. I have a six month old

baby, 3 children, all of them under the ages of 7. I don’t have any relation who wants to have

my kids. Please don’t send me to jail.

3. Argumentum ad populum (Appeal to the people)

This fallacy occurs when an arguer tries to win an argument. The arguer capitalises on the

need of man to be loved, admired, esteemed, valued, recognised and accepted. In this kind of

fallacy when an arguer excites the emotions and enthusiasm of a group of people in order to

get approval or acceptance of his conclusion. This is common during election campaigns.

Example:

Vote for me: I know you want a new Local Government, you want your children to go to

school free of charge, you want a generous man who will pay for your hospital bills. If you

vote for me, I will do all these and more.

4. Argumentum ad Hominem (Argument against the person).

There are three types of Argumentum ad Hominem, namely argumentum ad hominem

abusive and argumentum ad hominem circumstantial and the argumentum ad

hominem tu quoque.

4.1 Argumentum ad Hominem Abusive.

It is a form of fallacy that is not directed at the argument but at the person’s past or

background.

Examples:

Mr. John are argues that parents should increase pocket allowance of undergraduates

to N20,000. Mr. John never sent his kids to University even with best grades in

secondary school. He is, thus, incompentent to speak about undergraduates.

Mr. Alex is an expert in landscape design and has been brought to plan the landscape

of our community. Mr Alex is a drunk. We cannot therefore trust what he will do.

4.2 Argumentum ad Hominem Circumstantial

In this kind of argument, the arguer opines that the respondent is predisposed to

argue in a certain way because of the circumstance of his life.

Examples:

If Mr Ade says Nigeria will win in a match against Ghana. The Arguer says that Mr Ade says

so because Mr Ade was born in Ghana.

If Mr Brown argues that women cannot be president of Nigeria because women are the weak

sex, then the fallacy of argumentum ad hominem circumstantial is committed.

4.3 Argumentum ad Hominem “Tu quoque” (You too)

This fallacy is committed when the arguer argues that the respondent is guilty of the exactly

point he is trying to make in his argument.

Example: Arguer. Stop beating children

Respondent: But you also beat your kid last week.

Child to Dad: You said I should stop stealing biscuits in the supermarket. But you told me

yesterday that you stole biscuits as a child in supermarkets too.

5. Accident

This fallacy occurs when a general rule is misapplied to a specific cases that it was not

intended to cover. The general rule is cited to justify the particular case but wrongly

apllied.

Example:

Freedom of speech is guaranteed in the consitution. Therefore, Boko Haram should ba

allowed free speech if they come into the mosque.

6. Ignoratio Elenchi (Missing the point)

This fallacy ccurs when the premises are irrelevant to the conclusion. In other words, the

premises do not imply the conclusion.

Examples:

Premises: Crimes and robbery are increasing. Conclusion: We should reinstate the death penalty

Premise: There is so much corruption in the sytem.

Conclusion: Lets close the system.

7. Red Herring

This fallacy occurs when the arguer diverts the attention of the respondent to a different

topic entirely. Sometimes the diversion may be to a different topic subtly related to the

current argument or to a different topic entirely.

Examples:

Nuclear weapons are dangerous to health. As a matter of fact, Electricity is dangerous to

people’s life. Many people have died from electrocution. Care must therefore be taken in

dealing with electricity problems in the home.

Poisoned Fruits are rampant and there is need to inrease oversight functions of the

relevant agencies regulating fruits. Fruits are important for the health of the society.

Carrots are reach in Vitamins A, Brocolli iron. Therefore, people should eat more fruits.

FALLACIES OF WEAK INDUCTION

These fallacies occur because the connection between the premises and conclusion is not

strong enough to support the conclusion. Although the premises provide some level of

support, but they are not strong enough to cause one to believe the conclusion.

1. Argumentum ad Verecundiam (Appeal to Unqualified Authority)

This fallacy occurs when a cited authority lacks the credibility to be relied on to justify a

conclusion. Such a person may, for example, lack the requisite expertise, biased or

prejudiced or may motive to disseminate misinformation or may even lack the ability to

recall or perceive.

Examples:

Our family Physician says that nuclear bomb are made of atoms of deuterium and tritium.

Based on his expertise, it is true.

The Chairman of the Borado Tobacco testifies before the House Committee on the

dangers of smoking and argued that smoking does not have any dangers.

2. Hasty Generalisation (Converse Accident)

This fallacy is committed when a conclusion is drawn about all members from a class from

evidence from a selcted sample. In other word, the sample is not representative of the entire

group.

Examples:

Mr Jones BMW is having radiator problem. Miss Chioma Audi is having injectir issue.

Therefore all cars produced in Germany are bad.

Fulani herdsmen murdered people in Benue. Fulani herdsmen murdered people in Taraba.

Therefore all Fulani herdsmen are murders.

3. False Cause

This fallacy occurs when the link between the premises and conclusion is based on some

imaginary causal connection that probably does not exist or if it exists is not the cause of the

conclusion.

Any time the Enyimba Fans sing “All we are saying, give us more goals”, their team will

always loose the match. Therefore, Enyimba fans should not be singing that song during

matches.

Today, there are more laws and more crimes. To reduce the crimes, one must reduce the laws.

4. Weak Analogy

This fallacy occurs when the conclusionn is based on some analogy or similarity between two

things in which case the analogy is not stong enough to suppose drawing such a conclusion.

Maeegart bought a red dress and it was size 14 and cost 2000 naira. Lucy bought a dress that

is red and size 14. It will most likely cost N2000 naira also.

1. John, Micheal are law students, the wear black and white dresses Weak Analogy

This fallacy occurs when the conclusionn is based on some analogy or similarity between two

things in which case the analogy is not stong enough to suppose drawing such a conclusion.

Maeegart bought a red dress and it was size 14 and cost 2000 naira. Lcy bought a dress that is

red and size 14. It will most likely cost N2000 naira also.

John and Micheal are law students, the wear black and white dresses and they like pounded

yam and egusi soup

Agatha and Lucy are law students, they wear black and white dresses and will also like

pounded yam and egusi soup.

Fallacies of Presumption

They fallacies occur when the premises presume what the intend to prove in the conclusion.

These fallcaies include begging the question, complex question, false dichotomy and

suppresed evidence.

1. Petitio Principii (Begging the Question)

This fallacy occurs where there is an inadequate premises for a conclusion wherein the

arguer leaves out a false premises, restates a false premises as the conclusion or simply

reasoning in a circle. This fallacy requests the arguer to provide enough justification for

the conclusion, as the name implies “petitio principii” (request for the source). In the other

words, the source is absent whereas it is presumed to be present.

Murder is morally wrong. Judges who sentence people to be killed commit a morally

wrong act.

Apes and Humans come from the same ancestors. Just look at are similar they are.

Mark Zuckerberg founded Facebook. He pays his worker the highest salary in the world.

He can pay because he is the founder of Facebook.

2. Complex Question

This fallacy occurs when two or more questions are asked in a single question or argument

and a single anywer is given to both questions. The fallacy assumes the existence of a

certain condition and the respondent’s answer to the complex question confirms the

existence of that condition veiled implicitly in an argument. The aim is to trap the

respondent to accept a condition that he would ordinarily not accept.

Examples:

Have you stopped cheating in exams?

Yes: You were cheating but have stopped cheating

No: You are still cheting in exams

Have you stopped smoking?

Yes: You were smoking before and have stopped smoking

No: You are still smoking

3. False Dichotomy

This fallacy occurs when the premises of disjunctive argument (either…..or) present two

unlikely alternatives as if they are the only options present, and one of which is desirable and

the other not. In other words, the arguer proceeds to eliminate the undesirable alternative,

forcing the respondent to choose the other only remaining alternative. The argument is valid

but unsound.

Examples:

Dad, either you let me go on this excursion with my classmates or I will be miserable for life.

You don’t want me to be miserable for life. So you will let me go for the excursion.

Either you use this cream or your skin ratches will become cancerous. You don’t want to have

cancer. So you will buy this cream.

4. Suppressed Evidence

This fallacy is commited when an argument ignores some important piece of evidence that out

weighs the presented edivence.

Most dogs are friendly and pose to no threat to those who pet them. Therefore, it will be safe

to o pet the little dog that is approaching us now.

(The dog atually foams in the mouth which shows it have rabies and therefore poses a threat)

Enjoy Bambo lager beer. It will make you happy.

(This adverts ignores that alcohol is also dangerous to one’s health. With alcohol-related

health challenges, one cannot happy)

Fallacies of Ambiguity

They fallacies occur arise from some form of ambiguity in the premises, conclusion or both.

when the premises presume what the intend to prove in the conclusion. These fallacies include

Equivocation and Amphiboly.

1. Equivocation

This fallacy occurs when the conclusion of an argument depends on the fact that a word or

phrase is used, either explicitly and or implicity, in two different senses in the argument.

When such words are delibrately used to confuse the meanings in an argument, the fallacy

arises.

Some triangles are obtuse. Whatever is obtuse is ignorant. Therefore, some triangles are

ignorant

(Obtuse in the first sentence means a certain angle. Obtuse in the 2nd sentence means dull.

They do not mean the same thing)

James, the politician is our saviour. Jesus is the saviour of the world. Therefore, James is

Jesus.

(Saviour is the first sentence means one who has helped people from community problems.

Saviour in the second sentence means one who has come to save mankind from the sinful

state).

2. Amphiboly

Occurs when an arguer misinterpretes an ambib´guous statement and then draws a

conclusion based on the faulty interpretaion. The misintrepretation may arise from

missing comma, careless arrangement of words. The arguer then proceeds to use the

unintendedn interpretation and draws a conclusion based on it.

The tour guide said that standing in the Federal Secretariat Building, the State House can

be easily seen. Therefore, the State House in the Federel Secretariat Building.

(The arguer is the one who is standing not State House)

Micheal told Perry that he had made a mistake. Therefore, Micheal owned up to his

shortcoming.

(“he” is ambiguous. It could stand for Micheal or Perry. E.g. Micheal told Perry that he

(Michael) has made a mstake or Micheal told Perry that he (Perry) had made a mistake.)

Fallacies of Grammatical Analogy

They fallacies occur when when the argumentare used to argue some some connection in

linguistic structure whereas infact the connection or analogy are illegitimate or inappriopraite.

These include fallacies of Composition and Division.

3. Composition

This fallacy occurs when the attrbiute of a part is erroneously transferred to the whole. It

is argued that because the parts have certain attrbutes, therefore the whole has the same

attibute whereas the attributes of the parts cannot be legitimately transferred from the parts

to the whole.

John is an excellent player. Peter is an execeelnt player. Therefore the team is an excellent

team.

Every atom in this piece of chalk is invisible. Therefore, the chalk is invisible.

4. Division

This is the opposite of the fallacy of composition. The fallacy occurs when the attribute of

a whole is erroneously tranferred to its parts.

EUI is 3 years old. All students and staff in EUI are all 3 years old.

The soup is tasty. Therefore, salt used in cooking the soup is tasty

Definitions

Definitions have been a major preoccupation of logicians. Plato has argued that definitions

were meant to explain the meaning of certain external essences or forms such as piety,

justice,virtue. Definitions are meant to explain the meaning of word.

Definition is a group of words that assign a meaning to some word or group of words. Thus,

every definition is made up of two parts.

1. Definiendum: This is the word or group of words that is supposed to be defined.

2. Definiens: word or group of words that does the defining.

Example:

A tiger (Definiendum)

means

a large, stripped, ferocious feline indegenous to the jungles of Inda and Asia.( Definiens).

Types of definitions

1. Stipulative Definitions

This type of definition assigns meanig to a word for the first time. This may mean coining

a new word or giving meaning to an already existing word. The purpose is to replace a

more complex definition with a simpler one. This is usually as a result of a new

phenomenon.

Examples:

At the cross breeding of male tiger and female lion named=tigon

Male lion and female tiger=liger

Stipulative definition could also arise from the use of secret codes.

Examples

1. Operation Barbarossa= Name the Germans gave for the invadion of Russia.

2. Operation Crocodile dance= Name Nigerian Army gave to counter kidnapping

activities in the South East.

There is no true or false in stipulative definition.

2. Lexical Definitions

A lexical definition is used to report the meaning that a word already has in a language. E.g.

dictionary definitions. It can be true or false depending on whether it does or does not report

the way a word is used in a language. Lexical definitions removes ambiguity. An expression

is ambiguos when it can be interpreted to have two or more mening in a given context. E.g.

light, mad, bank.

He is mad (really mental case, intense anger)

3. Precising definition

This type of definition is used to reduced to reduce the vangueness of a word.A word is vague

if there are borderline cases in which it is impossible to tell if the word applies or does not

apply. E.g words such as fresh, rich, poor. Poor may be used to refer to someone who lacks

adequate necessities of life but in precising definition would be “Poor is used to refer to

someone who earns less than 50,000 monthly.

While stipulative dfintion is arbitrarily, precising definition is done with a great deal of care

and reflection.

4. Theoretical Definition

A theoretical definition assigns meaning to a word by suggesting a theory that gives a certain

characterisation to the entitities tthst the term denotes.For instance “heat” as he energy

associated with the random motion of the molecules of a substance suggest the deductive

consequnce from a text on the kinetic theory of heat. Example would ne John Staut Mill’s

definition of “good” as he gretest happiness of the greatest number” based on his utilitarian

theory of ethics.

5. Persuasive Definition

The aim of a persuasive defintion is to engender a favouraböe or unfavourabe attitude

towards hat is donatedby the definiendum. This is done by assigning an emotionally

charged or value-laden meaning to a word while making it seems as if the word really has

that meaning in that particular language in which it is used. It is a combination of

stipulative, lexical and theoretical definition.

Examples:

1. Taxation: means by which our commonwealth is preserved and sustained.

Taxation: procesdure used by beareucracies to rip off the people who elected them.

2. Capitalism: the economic system in which individuals ar afforeded the God-given

freedom o own propery and conduct business as they choose.

Capitalism: economic system in which humanity is sacrificed to the wanton quest for

money, and mutual understanding and respect are replaced by alienation, greed and

selfishness.

References

Copi, I. (1968). Introduction to Logic London: Macmillan. Kouassi, C. N. (2014). Fundamentals of Philosophy, Logic and Human Existence. Ibadan: Nelphil.

http://www.uky.edu/~rosdatte/phi120/lesson1a.htm. Accessed on 13.01.2018.

https://www.cs.utexas.edu/~schrum2/cs301k/lec/topic01-propLogic.pdf. Accessed on

13.01.2018.

http://www.tektonics.org/guest/fallacies.html. Accessed on 26.02.2018.

Copi, Irving M. and Carl Cohen 2002). Introduction To Logic (Eleventh Edition). Prentice

Hall. Upper Saddle River, NJ.

Hurley P. A (2006). Concise Introduction to Logic. Ninth ed. Belmont, USA:

Wadsworth/Thomson Learning.

Ujomu, P et al. (2011). Philosophy and Logic: An Introduction. Benin City: University of

Benin.