Please read ch. 3 of Richard Epstein's Critical Thinking

What makes a good argument?

We have defined "argument" and have practiced distinguishing arguments from non-arguments. We have said that the distinctive feature of an argument is that it is designed to convince a reader or a listener of a specific point or idea, known as the conclusion. The reason(s) given for accepting the conclusion of the argument are premises. An argument, as we have seen, is different from a passage designed to instruct or inform.

Of course, being able to identify an argument is of secondary importance to the task of knowing when it is reasonable or not to accept the conclusion of an argument. A person who presents an argument is trying to convince you of something. Should you accept that conclusion or not? Since we encounter many people in many situations who try to convince or persuade us to believe or do something, improving our ability to recognize good arguments and distinguish them from bad will have an enormous impact on the quality of our lives.

In discussing the criteria for good arguments, it is important to recognize that you already have developed -- through experience and past education -- the abilities to distinguish good from bad arguments, arguments that give good reasons to support the conclusion from those that do not. I hope these lessons will help you improve the skills you already possess.

A good argument is one in which the premises give good reasons to believe the conclusion is true. A good argument is one that presents a conclusion and then gives good reasons for accepting it.

Beware - this is not to say that convincing arguments are good arguments. Most of us at one time or another have been convinced by arguments that were not good. In fact, much of what we encounter on a daily basis -- from advertising, from politicians -- are designed to convince without giving good reasons. After taking this course, you should be less vulnerable to accepting bad arguments.

Beware:  To say that an argument is bad does not mean necessarily that the conclusion is false.  A bad argument is one in which the premises do not give good reason to accept the conclusion.  The conclusion may be true, but the reasons do not give good reason to accept it.

For an argument to be good, it must conform to the following three criteria:  (You must memorize these.)

1. The premises are plausible, that is, must have good reason to believe that the premises are true.

2. The argument must be valid or strong.

3. The premises are more plausible than the conclusion.

Please remember these three criteria; they form the basis of much that we will do in this course. Sometimes I will refer to these three rules in short hand fashion, as when I say a good argument must 1) have true premises, 2) be valid or strong, 3) premises more plausible than conclusion. Also, pleaes note that sometime I will not make reference to the last of the three criteria, which is not nearly as important as the first two.

The next several lessons will be devoted to understanding these three criteria. We can dispense with the third criteria rather quickly.

Criterion Three - Premises more plausible than conclusion

A good argument is one in which the premises are more plausible than the conclusion. This criteria means that an argument is not good if the conclusion is nothing more than a restatement of the premises, or when the conclusion rests upon a highly dubious (doubtful) premise or premises.

For example, consider this argument:

I am Adrian's best friend. I'm sure of this because she told me so, and I know she wouldn't lie to her best friend.

My premise that Adrian wouldn't lie to her best friend assumes the truth of the conclusion that I am Adrians best friend. We say that such an argument is circular; the argument is like a circle, you assume the premise to accept the conclusion, but you must assume the conclusion to accept the premise. We also say that such an argument begs the question. An argument that is circular, or which begs the question, fails to meet criteria three.

Consider this example:

My father was murdered by his brother (my uncle). I know this because the ghost of my father told me so.

In this argument (derived from Shakespeare's Hamlet), the speaker supports his conclusion with a premise that is highly dubious. Since it is not more plausible than the conclusion itself, this argument fails to meet criterion three.

Beware of examples like the following:

We don't need another liberal like Susan Stamper in the senate. She thinks the solution to every problem is to spend more money to create more government bureaucracies. Her policies are not conservative enough.

If this "argument" is stated loudly enough, and with a lot of rhetorical skill, you may be convinced by it. Yet, the premises say little more than what it is said in the premises. To call Susan Stamper a liberal and to say she likes to spend money and to say she is not a conservative is is to say much the same thing in different ways. Arguments that repeat the same idea in different words are also circular arguments. They fail to meet criterion three.

Criterion Two - Valid or Strong

We don't need to say much more about Criterion Three than what we have already said. Most of the time, circular argument, or arguments that beg the question are relatively easy to recognize. For this reason, I suggest that criteria one and two are much more important than three.

Criterion two says that for an argument to be good it must be valid or strong. We must spend some time discussing the meaning of these two terms. To demonstrate the meaning of the difference valid arguments and strong arguments, consider the following examples.

Example One: "Ladies and gentlemen of the jury: 1) The coroner has established that Mr. Watson was killed by a gun shot fired from within the house between 11:00 pm and midnight. 2) We also know that the gun was fired from a distance of approximately ten feet, 3) so Mr. Watson's death could not have been suicide. 4) Mrs. Watson was the only person in the house for the entire evening. 5) Mr. Watson was sitting by the fireplace and was not anywhere near an open window.  6)Mrs. Watson must have killed Mr. Watson.

Example Two: The weather report says that the hurricane may cause rain this afternoon. The sky is full of clouds and the wind is blowing. It's going to start raining soon.

Example One and Two are different primarily in the kind of support the premises provide for the conclusion. In example one, the lawyer is suggesting that the conclusion follows from the premises necessarily. Note the word "must" in the conclusion. To say the conclusion follows necessarily means that if the premises are true the conclusion must also be true. Or, to put it differently, it is impossible for the premises to be true and the conclusion false at the same time.

Look back at example one, can you think of any way or condition that would make it possible to have true premises with a false conclusion at the same time?

Claims 2 and 3 rule out the possibility of suicide, while Claim 1 rules out the possibility that Mr. Watson was shot by someone outside the house. Claims 4 and 5 fule out   rules out the possibility that some third party shot Mr. Watson.

Unless we accept some very unusual possibilities -- ie, the gun went off by itself; Mr. Watson's pet dog picked up the gun in his mouth and caused the gun to fire -- it would seem that the lawyer has presented an argument in which it is impossible for the premises to be true and the conclusion false at the same time.

Arguments in which it is impossible for the premises to be true and the conclusion false at the same time are valid arguments. The term "valid" then is reserved only for arguments in which the conclusion follows necessarily from the premises, that is, if the premises are true, the conclusion must also be true. In everyday conversation, people sometimes say, "His argument is valid" to mean that the argument is good, legitimate, or the conclusion true. In this class be sure to use valid only in the strict sense of the term.

Please note that even if we say that example one above is a valid argument, that does not make it a good argument. Remember for an argument to be good, it must be valid (or strong) AND have true premises. If we judge the argument to be valid, and the lawyer can establish the truth of each premise, it will be difficult to deny the conclusion, unless some new information is presented.

Look back at example #2. In this argument, the person making the argument does not believe that the conclusion that it will rain follows necessarily from the premises. He or she would readily admit that the premises could be true and the conclusion still be false at the same time, and that the conclusion probably follows from the premises. In other words, it is unlikely (though not impossible) for the premises to be true and the conclusion false at the same time.

Arguments in which the premises provide some degree of probable support for the conclusion are called strong arguments.

Note that a strong argument is, by definition, invalid. You must remember that when we say an argument is invalid, we are NOT saying it is a bad argument. Rather, we are saying simply that it it IS possible for the premises to be true and the conclusion false at the same time.) To say an argument is invalid is not to say the argument is bad. Remember the criterion is, For an argument to be good, it must be valid OR strong. An invalid argument may be strong. Hence, an invalid argument may be good.

The terms, "valid" and "strong" refer exclusively to the relationship betwen premises and conclusion, and the type of support provided by the premise(s) for the conclusion.

Because valid or strong refer to the relationship between premises and conclusion, these terms say nothing about the ACTUAL truth of the premises of an argument. To determine that an argument is valid or strong, is to maintain that IF the premises are true, then the conclusion either must be true (in valid arguments) or probably true (in strong arguments).

Test your understanding by answering each of the following:

1. A valid argument is one in which it is impossible for the premises to be true and the conclusion false at the same time. True or False. Explain your answer.

2. A strong argument is one in which it is nearly impossible for the premises to be true and the conclusion false at the same time. True or False. Explain your answer.

3. A good argument must be valid.

4. An invalid argument may be a good argument. True or false. Explain your answer.

5. A valid argument can have false premises. True or false. Explain your answer.

6. A valid argument must be good. True or false. Explain your answer.

7. It is impossible for an invalid argument to be a strong argument. True or False. Explain your answer.

8. A good argument must: have true premises, be valid or strong, and have premises that are more plausible than its conclusion.

9. If a valid argument has a false conclusion, then one of its premises must be false.

10. If a strong argument has a false conclusion, then one of its premises must be false.

After you have tried to answer these questions on your own, click below to get the answers.

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