[3.] Moral Reasoning.
Last week we considered three arguments about the Baby Theresa case, and we discussed whether any of those arguments is good or bad.
In this module, you will learn some new concepts that are essential to a precise examination and assessment of moral arguments—or arguments about any other subject matter.
These concepts come from another branch of philosophy:
logic (df.): the branch of philosophy that investigates arguments, especially how different kinds of arguments work and what distinguishes good arguments from bad ones.
There are two questions we must ask about an argument to tell whether it is good or bad.
First question: Are the premises true, or are they false? If all of the premises are true, then that is a good thing. If you are using an argument to try to convince someone that a claim (the argument's conclusion) is true, you definitely want to cite reasons (premises) that are true. But if an argument has one or more false premises, then it is a bad argument.
Consider this simple argument (RTD p.19)[1]:
(A) 1. All human beings are mortal.
2. Socrates was a human being.
3. Therefore, Socrates was mortal.
In argument (A), both premises are in fact true. All human beings are mortal. And Socrates (the ancient philosopher who was the teacher of Plato) was in fact human.
So far, so good: all of the premises in the argument are true, and that’s a good thing. But we have to consider something in addition to whether the premises are true, and that’s whether the premises logically support the conclusion. That’s what our second question is about:
Second question: Does the conclusion logically follow from the premises? In other words, if the premises were all true, would that guarantee that the conclusion is also true?
In argument (A), the conclusion does follow from the premises as a matter of logic: the premises being true forces the conclusion to be true. In other words, there is no way that the premises could be true without the conclusion being true too. Given that all humans really are mortal, and given that Socrates really was a human, then, as a matter of logic, it must be the case that Socrates was mortal. So in argument (A), the truth of the premises would guarantee the truth of the conclusion.
An argument in which the truth of the premises would guarantee the truth of the conclusion is said to be logically valid, or simply valid. It has:
validity (df.): A valid argument is one in which
1. the truth of the premises would guarantee the truth of the conclusion;
2. if the premises were true, then the conclusion would have to be true as well;
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 logically follows from the premises" is NOT an adequate definition of validity. To really understand what validity is, you must be able to state at least one of the definitions cited above.
· IMPORTANT: In logic and philosophy, the word "valid" does not mean the same thing that it means in ordinary English. For the purposes of this class, "valid" describes an argument that has the quality described 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.]
So argument (A) has all true premises and it is valid.
Here is another argument that has all true premises and is valid:
(B) 1. All mammals are animals.
2. All dogs are mammals.
3. Therefore, all dogs are animals.
Like the arguments about Baby Theresa, Arguments (A) and (B) are displayed in standard form: premises and conclusion are stated on separate, numbered lines and arranged so that the conclusion comes at the end.
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. What’s more, the conclusion might come before the premises. For example, Argument (B) could be written: "Of course dogs are animals; they're mammals, and all mammals are animals."
As we saw above, Arguments (A) and (B) have two characteristics: they have true premises, and they are logically valid.
But (and this is HUGELY IMPORTANT!) those two things have nothing to do with one another. Whether an argument has true premises doesn’t depend on whether it is valid. And whether an argument is valid does not depend on whether it has true premises. True premises, on one hand, and validity, on the other, are completely different things.
Consider this argument, which is valid (RTD p.20):
(C) 1. All people from Georgia are famous. [false!]
2. Jimmy Carter is from Georgia.
3. Therefore, Jimmy Carter is famous.
Despite the fact that this argument has a false premise, it still valid: if the premises were all true, then the conclusion would have to be true as well.
The same is true of this argument:
(D) 1. All US Presidents are from Chicago. [false!]
2. Barack Obama is a US President.
3. Therefore, Barack Obama is from Chicago.
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?
Here are some examples of arguments that are not logically valid … in other words, they are invalid:
(F) 1. Atlanta is located in Georgia.
2. The moon orbits the earth.
3. Therefore, Joe Biden is President.
Both premises are true, but this in no way indicates that the conclusion is true.
Here is another argument that is not valid, even though it has premises that are all true, and even though its premises are talking about the same subjects:
(G) 1. Some US Presidents are from Georgia.
2. Joe Biden is a President.
3. Therefore, Joe Biden is from Georgia.
Now, if the word “Some” in the first premise were replaced with the word “All”, then the argument would be valid … but that would just replace one problem (invalidity) with another: it would change the first premise from true to false:
(H) 1. All US Presidents are from Georgia. [False!]
2. Joe Biden is a President.
3. Therefore, Joe Biden is from Georgia.
OPTIONAL VIDEO: “Fundamentals: Validity” (Wi-Phi, 7:07) – I highly recommend that you watch this video!
When we critically evaluate an argument, we will be asking two related questions:
a) Are all of the premises true?
b. Is the argument logically valid?
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) has all premises all of which are actually true AND (2) is valid.
But if the answer to either question is "no," then the argument is unsound, and it has failed to prove that its conclusion is true.
The fact that an argument is unsound does not mean that its conclusion 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 this argument:
(I) 1. Atlanta is located in Georgia.
2. The moon orbits the earth.
3. Therefore, Kendrick Lamar is famous.
This argument has a true conclusion. But it is unsound because it is invalid. (It does have two true premises, but it is still unsound.)
It is also illustrated by this argument:
(J) 1. Beyonce is a nuclear engineer.
2. All nuclear engineers are famous.
3. So, Beyonce is famous.
This is valid, but it is still unsound (because it has false premises) – it also has a true conclusion.
OPTIONAL VIDEO: “Fundamentals: Soundness” (Wi-Phi, 5:14) – I also highly recommend that you watch this one!
There are some arguments that are good in their logical aspect, even though they are not valid. These are sometimes called inductive arguments.
· In these arguments, the truth of the premises would provide a very good reason for thinking the conclusion is true, but would not guarantee the truth of the conclusion. 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.[2]
Earlier we asked which of the following arguments is best:
The Benefits Argument (EMP p.3)
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.
The Argument that We Should Not Use People as Means (EMP p.3)
1. It is wrong to use people as means to other people's ends.
2. Taking Theresa's organs would be using her to benefit the other children.
3. Therefore, it should not be done.
The Argument from the Wrongness of Killing (EMP pp.4-5)
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.
QUESTION FOR FURTHER THOUGHT: which, if any, of these arguments about Baby Theresa is sound? In other words, which, if any, of these arguments (a) has premises that are both true and (b) is logically valid?
Information contained in these footnotes is provided in case you are interested in further reading. You will not be quizzed on the information given in these footnotes or on the websites to which they link.
[1] All of the cited material in this lecture comes from something that’s not in our textbook: James Rachels, “Some Basic Points about Arguments,” in The Right Thing to Do, 7th ed., ed. James Rachels and Stuart Rachels. New York: McGraw-Hill, 2015. In each citation, “RTD” stands for The Right Thing to Do.