Argument Relevance - Critical Thinking

Lecture 9

May 19, 2007

 

In order to look at the relevance of premises, you have to be making judgments.  If a premise is not relevant to the conclusion then it will not provide much (if any) support to the conclusion.

 

I. What is Relevance?

 

A  premise is relevant if it provides some reason, however slight, for accepting the truth of a conclusion.

 

 

1. Types of Relevance

a. If a premise provides support, it is positively relevant.

b. If a premise takes away support (is a counter-consideration), it is negatively relevant.

c. If a premise provides no support either way, it is irrelevant.

 

2. Some Other Things to Note

a. The issue of relevance only comes up when dealing with non-valid arguments.

b. If a premise is irrelevant, it does not matter whether it is acceptable.

c. If all the premises are irrelevant, the argument is dead in the water.

d. When dealing with linked premises, you must consider their relevance as a group.

e. Fallacies are groups of common irrelevant reasoning.

 

3.  When Can Irrelevance Occur?

a. If it is deliberately put there. ie. politicians using straw man arguments.

b. In the heat of a debate, problems like these can creep in (as opposed to carefully considered academic arguments.)

c. Irrelevance should be looked for, but falls under the 'logical self-defence' part of the course.   It is not much of an issue when someone has had time to think clearly about the issue at hand.

 

II. Fallacies of Irrelevance

 

1. Red Herring Fallacy

When one person in a debate, diverts the other from the issue at hand and causes them to debate the irrelevant issue.

 

2. Straw Man Fallacy

When someone refutes an unfairly weak, stupid or ridiculous version of their opponents idea because they do not understand it or they are deliberately being misleading about it.

 

3. Ad hominem fallacy

(argumentum ad hominem - argument addressed to the person)

 

There are three sub-types to this fallacy:

a. "Poisoning the well" - A direct attack upon the character of a person instead of attacking their argument.  In some cases, where honesty/character of person is important, this can be legitimate.

b. "Tu queu" (you too) - accusing the critic of the same thing the critic accuses you of instead of meeting the argument.

c. "The genetic fallacy" - Attacking the psychology or origin of a belief instead of the logical foundations of the belief.

 

4. Guilt by Association

Attacking another's position by linking it to a group that most people would find objectionable. ie. Nazis, Communists

 

5. Argumentum ad populum

(appeal to the populace)

Appealing to polls or "most people" instead of rational arguments.

 

6. Argumentum ad baculum

(appeal to violence)

Do as I say... or else!!!

 

7. Argumentum ad misericordium

Believe me or I will be unhappy....

 

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