1 BASIC CONCEPTS OF ARGUMENTS. What is an Argument? 2 To justify or defend a claim is to give reasons or arguments to support it. Reasoning (or inference)

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BASIC CONCEPTS OF ARGUMENTS

What is an Argument?2

To justify or defend a claim is to give reasons or arguments to support it.

Reasoning (or inference) is a psychological process.

When we express this process into words, we have arguments.

An argument is set of STATEMENTS (or propositions) composed of PREMISES and CONCLUSION such that the former supports the latter.


A STATEMENT is a sentence that is either T or F.

So questions, commands, requests are not statements.


The structure of an argument: Premise 1Premise 2Premise 3

: :

Premise n-----------------Conclusion


Example of argument:

Either CY Leung was speaking the truth or he was lying.

He was not speaking the truth.---------------------------------Therefore, he was lying.


Example of argument:

Most new students took DSE.He is a new student.--------------------------------------------------------He took DSE.


Conclusion indicators: therefore, hence, thus, so, as a result, wherefore . .

Premise indicators: since, for , because, as, given that, owing to . . .


SUB-CONCLUSION Sometimes, one or more of the premises of an

argument support a conclusion as a statement that in itself serves as a premise in the argument for the final conclusion. Such a statement is a sub-conclusion of the argument.


E.g.:1. Leon is a genius. (premise) 2. Geniuses are weird. (premise) 3. Therefore, Leon is weird. (sub-conclusion) 4. All weird people have problems in social relation.

(premise) 5. Therefore, Leon has problems in social relation.

(conclusion)


IMPLICIT (OR UNSTATED) PREMISE An implicit premise of an argument is a statement

that is assumed but needs to be added to the premises if they are to support the conclusion.


E.g.: What is the implicit premise in the following argument?

All murder is immoral. Therefore, mercy killing is

immoral.

E.g.: What is the implicit premise in the following argument?

Using pirate software violates the inventors’ property rights.

Therefore, it is wrong to use pirate software.

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Passages Similar to Arguments 13

EXPLANATIONS They have the same structure of arguments but the

reasons given in an explanation are not used to prove a claim. Instead, they are used to make sense of a claim that has already been well accepted.

E.g., “I am late because there is a traffic congestion."

Passages Similar to Arguments14

Conditional propositions They state that something will happen if certain

conditions are fulfilled. E.g., "if you work hard, you will pass the test."

Passages Similar to Arguments15

Statements of belief They simply express someone's beliefs without

providing any evidence to support those beliefs. E.g., "I believe that he is guilty and should be put

to jail."

The Logical Strength of an Argument 16

The logical strength of an argument is the measure of how its premises, assumed to be true, support its conclusion.

We divide arguments into two types according to their logical strength: Deductive arguments Inductive arguments

The Logical Strength of an Argument17

Deductive argument If all its premises are true, its conclusion is logically

impossible to be false. I.e.: The truth of its premises guarantees the truth of

its conclusion. E.g.: Either Albert or Bill is late. Albert is not late.

Therefore, Bill is late.

The Logical Strength of an Argument

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Inductive argument If all its premises are true, its conclusion is likely to be

true but still possible to be false. I.e.: The truth of its premises makes it reasonable to

hold that the conclusion is true. E.g.: Most people who are infected with HIV will

develop AIDS, and he is infected with HIV. Therefore, he will develop AIDS.

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1 BASIC CONCEPTS OF ARGUMENTS. What is an Argument? 2 To justify or defend a claim is to give reasons or arguments to support it. Reasoning (or inference)