The Structure of Arguments
An argument is a collection of statements, or claims, one of which is the conclusion, and the other statements are reasons, evidence, premises, or supporting statements. The aim is to show that the conclusion is True or that it is more Reasonable to accept it as true.
1) If Bill Clinton is a bulldog,
then he has four legs.
2) Bill Clinton is a bulldog!
3) Therefore, . . . Conclusion? You know the answer: Bill has four legs.
How did you know that? Not because if any empirical facts you know. For you probably know that Bill is a man. But the conclusion follows logically from the premises. IF the premises are true, THEN the conclusion is true. Why? Because the reasoning follows the rules of deductive logic:
1) If A, then B
2) A
3) Therefore B
But it is not a Sound
deductive argument, although it is logically valid, all its premises are not
true. A Sound deductive argument
must be both logically valid and its premises must be true.
Now we want valid arguments even if we are not sure if the supporting premises are true. So when we are reading an argument, or hearing someone’s argument, we need to ask if we have a valid deductive argument.
How do we detect a valid argument?
The easiest way is to ask questions, questions that propose counter examples.
Example:
IF Joe took a shower, then he got wet. (If A then B)
Joe didn’t take a shower (Not A)
Therefore, he did not get wet. (Therefore, not B)
Is this a valid deductive argument?
It is easy to see that it is not. The premises may well be true. But we can see that the conclusion does not follow from the premises. Maybe Joe got wet in the rain. The problem is that this argument does not follow valid rules of deductive reasoning.
Usually, however, we encounter arguments that are valid but they are not sound because the premises are not true, as in the Clinton example.
And premises are usually established by inductive reasoning.
With inductive arguments the conclusion is established by supporting evidence or grounds. And we call a good inductive argument Warranted.
The errors in inductive arguments are not simply related to false evidence, but there are typical problems with the reasoning:
Joe takes two aspirin every day.
Joe never has a cold
Therefore, aspirin prevents colds.
The conclusion is that aspirin prevents colds. But let’s analyze the reasoning. We might say that we are trying to establish why Joe does not have colds. We know that Joe never has a cold; we know this to be true from our long experience with him. So let’s say that that piece of supporting evidence is true. But what is the explanation for this? We are looking for a casual relationship; a relationship between cause and effect. The effect is Joe has no colds, but what is the cause of this? And of course here is where that argument goes bad.
2. Second, might there be other explanations for Joe’s good health? No care has been taken to rule out other explanations—no control group.
3. As well, with causal generalizations we must remember that statistical links are not necessary causal links; more experiments might be needed.
In general we are trying to reason as the scientist reasons, we are trying to pile up evidence, collect supporting reasons, use numerous cases, for our general thesis, or conclusion. The more evidence, the bigger our sample, the more reasonable our conclusion.
But we need to remember that inductive reasoning can never absolutely establish its conclusion, it can only to so to a greater or lesser degree. So we need to strive to construct the most warranted argument, or accept only the most well founded inductive argument. And always be humble in our conclusions.
Moral Reasoning
Let’s look at an example to see how all this applies to moral argumentation. When we look at the issues in the next sections, we will see many arguments, but they will not always be in neat logical form, and so we will take some effort to see if we can reconstruct the argument that author is putting forth. Generally that means trying to put the argument into a deductive form, and then examining the premises to see how they are established.
People often claim that Homosexuality is morally wrong. That, we might say, is their conclusion: “Therefore, homosexuality is morally wrong.” But how do they support it?
General premise (a
normative premise when making a moral argument.)
1. Unnatural activities are morally wrong
Particular empirical premise
2. Homosexuality is an unnatural activity
Conclusion
3. Therefore, homosexuality is morally wrong.
All A is B; (A = unnatural
activities, B = morally wrong)
C is A. (C = homosexuality, A = unnatural)
Therefore C is B (C =
homosexuality, B = morally wrong)
Lets examine the premises
First the empirical premise.
“Homosexuality is unnatural.”
First critical question: what does this mean?
It means that this activity is 1)
never seen because it violates the laws of nature?
2) Tends not to happen since it is outside the unusual course of events?
3) Is not normal?
What is an example of an unnatural activity? Is shaving unwanted body hair unnatural? If it is, then it would be morally wrong; but that seems crazy.
There seems to be considerable doubt about the very meaning of the claim. The premise seems very doubtful.
Thinking of counter examples to a very general premise (whether empirical or normative) is one way to cast doubt on an argument; we are breaking down the generalization.
Then we need to think of a way to revise the premise if we can. Can we here?
Only if unnatural can be reconstructed to mean something like, “goes against what is known to lead to a good or fulfilling human life,” then we might have an argument.
If a key term in the factual premise (unnatural) is in doubt, then the normative premise (unnatural activities are wrong) is in doubt too!
Another way to challenge an argument is to challenge the moral premises or assumptions, and that is what we have also been doing here. The basic assumption has to do with making a distinction between natural and unnatural, and then calling the unnatural morally wrong.
But even if we accept the factual premise, how does the normative premise fare? How is it that unnatural activities are wrong? They might be stupid, but what do we need to say something is morally impermissible?
That it violates a plausible moral principle.
So one way to test our moral assumptions is to consider some hypothetical cases or counter examples and see if we still agree? We will do this extensively in the abortion debate.
Adapted from Barry and Olin, Applying Ethics, Wadsworth, 1999.