Chapter 4: Lecture Notes

Good Arguments:

An Introduction

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We are going to set forth the conditions for evaluating an argument. There are lots of different kinds of argument and terms for which we evaluate them, but the most basic term we are going to use for argument evaluation is:

Cogent

If the premises of an argument are rationally acceptable and are ordered so as to provide rational support for the conclusion, then the argument is cogent.

The conditions for cogency are the ARG conditions.

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The ARG conditions are:

(1) Acceptable premises – it is reasonable for the person receiving the argument to believe the premises to be true

(2) Relevant premises – premises are relevant to the conclusion

(3) Good grounds – the premises support the conclusion and make it reasonable to believe the conclusion

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This means that cogency of an argument requires acceptable premises, relevant premises, and good grounds.

It is easy to remember the requirement for cogency because the ARG conditions are the first three letters of what we are evaluating: ARGuments.

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More on the R and G conditions

There are at least four ways premises can support conclusions for which we will evaluate:

(1)Deductive entailment

(2)Conductive support

(3)Inductive support

(4)Analogy

The R and G conditions vary with each type of argument.

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(1)Deductive entailment

Often referred to as simply validity, deductive entailment is a tight logical relation where the when the premises are true, so must the conclusion be true.

Consider the following argument: Only members are allowed into the club. Andrew was not allowed in. So, Andrew is not a member of the club.

If the premises are true, then conclusion has to be true.

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For deductively valid argument it is never possible for the conclusion to be false when all the premises are true.

Another way to this of this is to say that when the premises are true, the conclusion must be true.

Validity does not come in degrees. Argument are either valid or they are not valid.

Deductively valid arguments satisfy both the R and the G conditions for cogency of arguments.

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(2) Conductive support

In conductive argument, the premises are put forth convergently, not in a linked way as with validity, so as to support the conclusion. (Chapter 12 deal with these kinds of arguments in particular)

Legal cases often involves conductive reasoning. Decisions for buying a house could work conductively as well.

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Consider reasons to buy a house.

Fireplace, pool, close to school, close to work, affordable, good neighborhood, gardening area, nice garage, and so on.

Many of these aspects are reasons to buy the house. As a collection, they make a cogent case for purchasing the house. The same could occur in a legal case for a person on trial. For example: no alibi, motive, eye witness testimony, are all reason to suspect the person.

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The notion of a counterargument is important with conductive arguments. For example, if the sales person pointed out the pool as a selling point, but the potential buyer cannot swim, then that would undermine the reason to buy the house. But there are still other reason to buy the house: price, location near a school and so on.

The same for the legal case. If the eye witness didn’t pick the defendant out of a line up, there is still the other evidence against him.

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(3) Inductive support

Sometimes referred to as abductive arguments (and chapters 9 and 10 are devoted to them) inductive support is evidence (as opposed to reasons) that support the conclusion in a manner less than that of deductively valid arguments.

Typically inductive argument rely on regularities in the world to make reasonable predictions.

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One kind of inductive argument is a generalization about an entire population based on an observed sub group of the population.

If all the people I meet from Ohio are football fans, and I meet Sue from Ohio. Then there is good reason for me to think that she is a football fan (depending on how many people I have observed from Ohio).

Inductive argument with all true premises don’t guarantee the truth of the conclusion the way valid argument do.

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(4) Analogy

Analogical reasoning occurs in medicine, law, science, and daily life.

Imagine that a new store opens in your neighborhood, say a Sears. You have been in many Sears stores and conclude from other Sears stores you have been in that this new Sears store will have Kenmore appliances.

This is a kind of analogy.

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Analogies have to have relevantly similar properties. So, if the new store wasn’t Sears, but just a big store or if it was Sears, but an clothing outlet Sears, then there would be some relevant dissimilar properties involved.

We will spend a lot of time looking an analogies in chapter 11.

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Using the ARG conditions to evaluate arguments.

Start with the A condition (are the premises acceptable?)

If so, then move to the R condition (are the premises relevant to the conclusion?)

If so, then move on to the G condition (do the premises provide good grounds?)

If ARG are satisfied, then we have a cogent argument.

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Failing the (A) Condition

If the premises are not acceptable (and there are lots of reasons this might happen), then the argument fails the (A) condition.

Premises that are clearly false, contain persuasive definitions, or are disputable based on common knowledge are examples as to why premises might not be acceptable. See example pages 95-6.

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Failing the (R) Condition

If an argument has acceptable premises, we can then ask if the premises are relevant to the conclusion. If for some reason, they are not relevant to the conclusion, then the argument is not cogent.

If the argument fails the (R) condition, we do not have to move on and test for (G) since we know the argument is not cogent. See example on pages 97-8.

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Failing the (G) Condition

If an argument satisfies both the (A) and (R) conditions, we can move on to the (G) condition.

If the premises of an argument are true and relevant to the conclusion, the next question is about grounding. Do these relevant, well supported premises actually support the conclusion. If so, then we have a cogent argument. If not, then we don’t. See example on pages 98-9.

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The Significance of Argument Evaluation:

When we claim that an argument is not cogent, we are claiming that the author of the argument has failed to justify the conclusion with adequate reasoning from adequate premises. But this is to object to the argument as a whole.

Remember: objecting to an argument is not the same thing as objecting to the truth or falsity of the conclusion. (103)

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The Challenge of Argument

Arguments serve as a fundamental tool for rational persuasion. Putting forth an argument is to do the following:

(1) Asserts the premises

(2) Asserts if that the premises are acceptable the conclusion is acceptable

(3) Asserts the conclusion.

The challenge of argument is to construct and respond to argument in a way that is appropriate to the basic structure of argument. (104)

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Confirmation Bias:

People tend to reject argument when the don’t agree with the conclusion. This is not an acceptable way to evaluate an argument for cogency.

This psychological phenomenon is called confirmation bias.

We all need to be aware and carful of confirmation bias when evaluation argument as cogent or not. (106)

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Cogency, Soundness, and Validity

Deductive entailment (validity) satisfies the (R) and (G) requirements completely. Sound arguments have all true premises and thus satisfy (A). So sound arguments are cogent.

But there are other arguments that are cogent, but not sound because they are either not valid or have premises that are rationally acceptable, but not true. We will spend time on soundness in Chs 7 and 8. (108)

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Evaluating and Constructing Arguments

When an argument is offered, there are three possible ways to respond to an argument:

(1)Reasoned acceptance -- ARG are accepted

(2)Reasoned rejection -- one or more of ARG are not accepted

(3)Suspended judgment -- for various reason you might suspend judgment on the argument

See pages 109-10

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The Dialectical Context

The dialectical context is the context of discussion and deliberation about an issue. (111-12)

It is the back and forth nature of giving and evaluating argument about a particular topic.

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Terms to review:

Acceptability of premises Analogy

ARG conditions Cogent argument

Conductive argument Deductive entailment

Deductive validity Dialectical context

Goodness of grounds Inductive support

Rational persuasion Relevance of premises

Sound argument Validity