[2.6.] Arguments That Are Not Valid.

 

We have looked at two types of argument:

·         valid, all premises true

·         valid, some premises true, some premises false

What might an invalid (non-valid) argument look like?

 

 

C.

1. Atlanta is located in Georgia. (premise) (T)
2. The moon orbits the earth. (premise) (T)
3. Therefore, Barack Obama is President. (conclusion) (T)

 

The tight connection between the premises and the conclusion found in arguments (A) and (B) is missing. Both premises are true, but this in no way indicates that the conclusion is true. In fact, the premises and the conclusion have nothing to do with each other. The same is true of Rachels’ argument #3 (RTD, p.21).  Both my argument C and Rachels’ argument #3 are invalid. Here is another invalid argument, but this one isn’t so obviously invalid:

 

 

D.

1. Some US Presidents are from Georgia. (T)
2. Barack Obama is a President. (T)
3. Therefore, Barack Obama is from Georgia. (F)

 

invalidity (df.): An invalid argument is one in which the truth of the premises would not guarantee the truth of the conclusion. I.e. (in other words) it is possible for the premises to be true and the conclusion false at the same time.

 

 

[2.7.] Soundness.

 

When we critically evaluate an ethical argument, we will be asking two related, but distinct, questions:

1. Is it valid? [concerns the LOGICAL ASPECT of the argument]

2. Are all of the premises true? [concerns its FACTUAL or MATERIAL ASPECT]

 

If the answer to both questions is “yes,” then the argument is said to be sound.

 

soundness (df.): A sound argument is an argument that (1) is valid and (2) has all true premises.

 

But if the answer to either question is “no,” then the argument is not sound, and we should reject it.

 

So (A) is sound, since it meets both of these conditions; (B) is unsound, since it has a false premise; and (C) and (D) are unsound, since they are not valid.

 

The fact that an argument is not sound does not mean that its conclusion is false. Showing that an argument is bad is very different than showing that the conclusion of the argument is false. All that can be concluded from the fact that an argument is unsound is that the conclusion has not been proved true by that argument, and a different argument is needed to support the conclusion. This is illustrated by (C).

 

There are some arguments that are good in their logical aspect, even though they are not valid. For the most part, we will not be discussing those types of arguments in this class. The majority of the arguments we discuss in this class will be either valid or logically bad. To learn about these other types of arguments, you can take the Philosophy Program’s Critical Thinking course (PHIL 2110; 3 hrs credit in core area B).

 

 

[2.8.] The Limited Cultural Differences Argument.

 

To illustrate some further, simple points about philosophical arguments, we will consider a specific ethical claim, as well as an argument for this claim.

 

Different societies disagree about the morality of certain actions. For example, in traditional Eskimo (Inuit) society, infanticide (df.: the killing of a newborn baby) is believed to be morally permissible (not morally wrong) in certain circumstances (in these circumstances, it is left up to the parents to decide whether to kill the infant; there is no social stigma attached to the practice; it is more common with baby girls than with boys).

 

But in contemporary American society, killing an infant is believed to be morally wrong, no matter what the circumstances. (You will read more about this practice of the Eskimos in EMP 2.5).

 

Here is the argument that Rachels asks us to consider (argument #4 on RTD p.23). I will call it the Limited Cultural Differences Argument (LCDA) (I have changed it slightly to make it clearer; I have also given it a different name than it has in the textbook):

 

1.      In some societies, infanticide is believed to be morally permissible (not morally wrong).

2.      In other societies, infanticide is believed to be morally wrong.

3.      Therefore, infanticide is neither objectively permissible nor objectively wrong; there is no objective fact of the matter, only beliefs about whether or not it is morally wrong.

 

 

[2.8.1.] Objectivity.

 

The word “objective” plays a crucial role in the Limited Cultural Differences Argument (LCDA). The word is a familiar one, but it is not the easiest term to define precisely.

 

In the LCDA, the word “objective” means something like this:

 

objective (df.): something is objective when it is independent of what anyone believes, thinks, or feels about it.

·         For example, “it is objectively true that p” =  “it is true that p, whether or not anyone believes that p.” It is an objectively true that the earth orbits the sun, that 2+2=4, etc.

·         A synonym for “objective” is “real.”[1]

 

“Objective” is the opposite of “subjective.”

 

subjective (df.): something is subjective when there is no truth or fact of the matter about it, only opinions/beliefs or feelings. For example, whether Low-Carb Rock Star is delicious is a subjective matter.

 

In the definition of “objective,” the phrase “about it” is very important—some objective facts depend on what someone thinks (or feels, or believes) without depending on what anyone thinks (or feels, or believes) ABOUT THOSE FACTS.

 

For example, facts about a person’s mental states:

·         Amy thinks that Atlanta is beutiful..

·         Bill feels sad that Michael Jackson died.

·         Craig believes that Montgomery is the capitol of Alabama.

 

Each of these facts depends on what someone thinks, feels or believes. For example, the fact that Amy thinks that Atlanta is beautiful depends on what someone thinks: it depends on what Amy thinks, because it is a fact about what Amy thinks.

 

Yet, it is still an objective fact about Amy. It is objectively true of her that she thinks that Atlanta is beautiful. This is an objective fact about Amy’s mind.

 

It is an objective fact because it does not depend on what Amy or anyone else thinks about it. We can not make it the case that Amy thinks that Atlanta is ugly simply by thinking that she thinks that. In other words, we cannot change that fact about her simply by our beginning to think that she thinks that Atlanta is hideous. This is what makes it objectively true of Amy that she thinks Atlanta is beautiful.

 

 

[2.8.2.] Is the LCDA a Sound Argument?

 

Since “sound” means: (a) having all true premises and (b) valid, we can split this question into two parts:

 

(a) Are both of the premises true?

 

(b) Is the argument valid?

 

If the answer to either question is “no”, then the argument is unsound, and we should reject it.

 

 

Stopping point for Friday August 21. For next time:

·         study the lecture notes from today, and finish reading RTD ch.2 (pp.25-28); you may have a pop quiz on both at the beginning of class;

·         especially study the notes regarding objectivity and the Limited Cultural Differences Argument; be prepared to discuss whether or not Rachels is right in saying that that argument is invalid.