2.4 Strong Vs Weak Arguments

1. If an argument form is valid, like the one below … 1. All A are B 2. x is an A Therefore, x is a B … then all arguments that share this form are also valid.

True

False

True. This is a fundamental property of valid argument forms, that they're FORMS. Validity is a property of the structural features of an argument, it's independent of the specific claims that are being asserted.

Explanation

True. This is a fundamental property of valid argument forms, that they're FORMS. Validity is a property of the structural features of an argument, it's independent of the specific claims that are being asserted.

2. An argument can be invalid but still qualify as a good argument.

True

False

True. If it's strong then it'll qualify.

Explanation

True. If it's strong then it'll qualify.

3. An argument can have weak logic but still qualify as a good argument.

True

False

False. Weak arguments violate the Logic Condition, by definition.

Explanation

False. Weak arguments violate the Logic Condition, by definition.

4. 1. Almost all movies filmed in the past decade are in black and white. 2. The Hunger Games movie was filmed in the past decade. Therefore, The Hunger Games is a black and white movie.

Strong

Weak

Strong. If the premises are true, the conclusion is very likely true. The first premise is in fact false, but that's irrelevant to assessing the logic of the argument.

Explanation

Strong. If the premises are true, the conclusion is very likely true. The first premise is in fact false, but that's irrelevant to assessing the logic of the argument.

5. Validity comes in degrees — you can have arguments that are "very valid", "moderately valid", etc.

True

False

False. Validity is all-or-nothing, it doesn't come in degrees.

Explanation

False. Validity is all-or-nothing, it doesn't come in degrees.

6. The threshold between "weak" and "strong" arguments isn't fixed or specified by logic. It's a conventional choice that we make.

True

False

True. The threshold between "weak" and "strong" arguments is a choice that we make, it's not dictated by logic.

Explanation

True. The threshold between "weak" and "strong" arguments is a choice that we make, it's not dictated by logic.

7. 1. Almost all movies filmed in the past decade are in black and white. 2. The Hunger Games movie is a black and white movie. Therefore, The Hunger Games was filmed in the past decade.

Strong

Weak

Weak. Even granting the premises, the conclusion would not follow with high probability. One could have many movies filmed prior to the past decade that were also in black and white.

Explanation

Weak. Even granting the premises, the conclusion would not follow with high probability. One could have many movies filmed prior to the past decade that were also in black and white.

8. "90% of the people surveyed at my local church support capital punishment. This gives us reason to believe that most Americans support capital punishment."

Valid

Strong

Weak

Weak. The sample is too small and unrepresentative to let us infer that most Americans think the same way as the local church goers about capital punishment.

Explanation

Weak. The sample is too small and unrepresentative to let us infer that most Americans think the same way as the local church goers about capital punishment.

9. 1. Very few people are taller than 7 feet. 2. James is a person. Therefore, James is not taller than 7 feet.

Valid

Strong

Weak

Strong. Given the premises, it's very likely that James is not taller than 7 feet.

Explanation

Strong. Given the premises, it's very likely that James is not taller than 7 feet.

10. 1. If I study hard then I'll pass the final exam. 2. I passed the final exam. Therefore, I studied hard.

Valid

Strong

Weak

Weak. The premises don't say that the ONLY way to pass the final is to study hard. They only say that IF I study hard then I'm sure to pass. But I could still pass without studying hard (because the questions were easy, because I cheated, because I'm really smart, and so on...).

Explanation

Weak. The premises don't say that the ONLY way to pass the final is to study hard. They only say that IF I study hard then I'm sure to pass. But I could still pass without studying hard (because the questions were easy, because I cheated, because I'm really smart, and so on...).