PHIL 2030: Introduction to Ethics
Dr. Robert Lane
Lecture Notes: Tuesday January 9, 2014

 

[2.] Logic

 

 

[2.1.] Arguments, Reasons, and the Minimum Conception of Morality.

 

Like all areas of philosophy, ethics is not a matter of simply saying what you believe or feel about a given issue.

 

But unlike the sciences, philosophy does not usually depend on specific sorts of empirical observation, gathering data, performing experiments, or making calculations.[1]

 

But on the other hand, philosophers do not simply announce their theories to the world without any evidence to back them up. Philosophy, including ethics, depends on reasoning and evidence. Philosophers test existing theories, and develop new ones, primarily by reasoning. They give arguments to support their claims:

 

argument (df.): a set of statements some of which (the argument’s premises) are intended to serve as evidence or reasons for thinking that another statement (the argument’s conclusion) is true.

 

A philosophical claim—and thus, an ethical claim—is only as good as the arguments that one can give to support it. Because of this, most (but not all) philosophical work consists in arguing in support of philosophical claims.

 

In ethics, if you believe that something is immoral or that it is morally permissible, you need to be able to back up that belief with good reasons. You need to be able to provide reasons for thinking that your belief is true. In other words, you have to be able to give an argument for your belief.

 

Suppose you say that in general, theft is immoral. If I ask you why you think this is the case, then you ought to be able to give me a reason, e.g., “It harms the person from whom something is being stolen.” This may be a good argument in support of the claim that, in general, theft is wrong. (A worse argument in support of that claim is: “Sometimes you end up stealing low quality goods and it’s really not worth the effort.”) If you can give no reason for asserting that theft is wrong, then I am within my rights to ignore you. This illustrates that morality is based on reasons.

 

This is much different than saying, e.g., “Turkey & Gravy flavored soda is delicious![2]” or “Rancid goat’s milk is tasty.” These are acceptable statements, even if I have no reasons to give in support of them. In this way, moral claims are much different than claims of personal preference.

 

This is a point that the author of EMP, James Rachels, emphasizes when he describes what he calls the Minimum Conception of Morality:

 

Morality is, at the very least, the effort to guide one’s conduct by reason—that is, to do what there are the best reasons for doing—while giving equal weight to the interests of each individual affected by one’s decision. (13)

 

This combines two ideas:

  1. “moral judgments must be backed up by good reasons”;
  2. “morality requires the impartial consideration of each individual’s interests.” (10)

 

 

[2.2.] Arguments About Baby Theresa.

Once again, here are the arguments about Baby Theresa... (these are discussed in ch.1 of Elements of Moral Philosophy (EMP), one of your two textbooks; here I’m quoting directly from EMP p.3, although I’m wording and formatting the arguments a bit differently):

 

The Benefits Argument

1.      If we can benefit someone, without harming anyone else, we ought to do so.

2.      Transplanting the organs would benefit the other children without harming Baby Theresa.

3.      Therefore, we ought to transplant the organs.

 

But it is important to be able to evaluate such arguments, i.e., to tell whether they are good or bad. One reason this is so important is that frequently there are competing arguments, i.e., arguments with opposite conclusions. This argument’s conclusion disagrees with the conclusion of the Benefits Argument (quoting from EMP, p.4):

 

The Wrongness-of-Killing Argument

1.      It is wrong to kill one person to save another.

2.      Taking Theresa’s organs would be killing her to save others.

3.      So taking the organs would be wrong.

 

Part of your reading for today (EMP ch.1) describes arguments relevant to two other controversial cases: Jodie and Mary (the conjoined twins) and Tracy Latimer (the 12-year-old girl with cerebral palsy[3]).

 

Rachels makes an important point about these three cases:

 

The cases of Baby Theresa, Jodie and Mary, and Tracy Latimer are liable to arouse strong feelings. Such feelings are often a sign of moral seriousness and may be admired. But they can also get in the way of discovering the truth: When we feel strongly about an issue, it is tempting to assume that we just know what the truth is, without even having to consider the arguments on the other side. Unfortunately, however, we cannot rely on our feelings, no matter how powerful they may be. Our feelings may be irrational; they may be nothing but the products of prejudice, selfishness, or cultural conditioning. At one time, for example, people’s feelings told them that members of other races were inferior and that slavery was God’s plan.

Moreover, people’s feelings can be very different. In the case of Tracy Latimer, some people feel very strongly that her father should have been given a long prison term, whereas others feel equally strongly that he should never have been prosecuted. But both of these feelings cannot be correct. (EMP 10-11, emphasis added)

 

Because people sometimes disagree about what is morally right, and because it is usually possible to give arguments for each side of a moral issue, we must be able to evaluate moral arguments. In other words, we must be able to tell good arguments about morality from bad ones.

 

To do this, we will need to take a lengthy detour out of ethics and into logic and consider some basic logical concepts. In particular, we need to fully understand the following concepts from logic:

·         validity and invalidity

·         soundness.

 

 

[2.3.] Validity.

 

Consider the following simple argument:

 

A.

  1. All mammals are animals. (premise)
  2. All dogs are mammals. (premise)
  3. Therefore, all dogs are animals. (conclusion)

 

NOTE: Like the arguments about Baby Theresa, Argument A is displayed in a way that makes it very explicit which statements are the premises and which is the conclusion. But most of the time, when you come across an argument in your reading (even in your philosophy reading), it will not be indented from the margin, with each statement on a separate line. Normally, it will be written in prose form.  Further, the conclusion may come before the premises. For example, Argument A could be written: “Of course dogs are animals; they’re mammals, and all mammals are animals.”

 

The word “therefore” indicates that the conclusion is supposed to be supported by the premises.

 

Notice that in argument (A) there is a

·         very tight connection between premises and conclusion; more specifically:

·         the conclusion follows from the premises; this means that

·         if the premises were true, then the conclusion would have to be true as well.

 

The same is true of Rachels’ argument #1 (RTD, p.19): if the premises were true, then the conclusion would have to be true, as well.

 

This “follows from” property shared by arguments (A) and (1) is known as validity.

 

validity (df.): A valid argument is one in which

1.      if the premises were true, then the conclusion would have to be true as well.

2.      the truth of the premises would guarantee the truth of the conclusion;

3.      it is impossible for the premises to be all true and the conclusion to be false at the same time.

·         These are three equivalent ways of defining validity.

 

·         To say “the conclusion follows from the premises” is NOT an adequate definition of validity. To really explain what validity is, you must give at least one of the definitions cited above.

 

·         IMPORTANT: In logic and philosophy, the word “valid” does not mean exactly the same thing that it does in ordinary English. For the purposes of this class, “valid” means only what it is defined to mean above: if the premises were true, then the conclusion would have to be true, as well. [Sometimes, this sort of validity is called deductive validity.]

 

It is important to remember this point, because some valid arguments have false premises…

 

 

[2.5.] Valid Arguments With False Premises.

 

Another example of a valid argument:

 

B.        

  1. All US Presidents are from Chicago. (premise)
  2. Barack Obama is a US President. (premise)
  3. Therefore, Barack Obama is from Chicago. (conclusion)

 

Despite the fact that this argument has a false premise, it still has the same tight connection between premises and conclusion: the conclusion follows from the premises. In other words, it is valid. The same is true of Rachels’ argument #2 (RTD, p.20): it is a valid argument with a false premise.

 

In summary: the validity of an argument does not depend on whether the premises are actually true or false.  So far as validity is concerned, it does not matter whether all of the premises are actually true, some of them are actually true, or none of them is actually true. When you think about whether an argument is valid, do not ask whether the premises are actually true or false. Instead, ask: if the premises were true, would the conclusion then have to be true, as well?

 

It is important to define validity this way:

1. if the premises were true, then the conclusion would have to be true as well.

2. the truth of the premises would guarantee the truth of the conclusion

 

 …instead of this way:

(*)  if the premises are true, then the conclusion must be true as well;

the truth of the premises does guarantee the truth of the conclusion.

 

(*) are not good definitions of validity, because they imply that the premises must actually be true in order for the argument to be valid. But that’s wrong: the premises do not actually have to be true in order for the argument to be valid.

 

 

[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.20).  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.

 

Stopping point for Thursday January 9.  For next time:

·         study today’s lecture notes;

·         continue reading RTD chapter 2: pp.21-24 only.

You may have a pop quiz over all of this material (today’s lecture notes and the assigned reading) at the beginning of the next class. Also, if you have not already done so, read the syllabus thoroughly.

 

 



[1] I say that philosophy does not usually depend on these things because of the so-called experimental philosophy movement. See “The Experimental Philosophy Page,” URL = < http://pantheon.yale.edu/~jk762/ExperimentalPhilosophy.html >, retrieved on August 23, 2012.

[2] This is a real thing. See http://content.time.com/time/specials/packages/article/0,28804,1913612_1913610_1913571,00.html .

[3] A recent summary and update of the case of Robert Latimer, who killed his daughter Tracy, is here: “'Compassionate homicide': The law and Robert Latimer,” CBC News, URL = < http://www.cbc.ca/news/background/latimer/ >, accessed August 23, 2011.




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