Phil 102: Lecture concerning Arguments with Sub-Arguments PDF

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Philosophy 102: Critical Thinking/Reasoning Instructor’s Lecture on Arguments with Sub-Arguments

There are at least two reasons an argument might have a sub-argument. Here is one reason: Someone has actually challenged a premise of an argument, and the author of the argument has supported the challenged premise with another statement. The reason a premise is vulnerable to a challenge is because it is an unsupported claim. Here is another reason: The author of an argument needs a particular premise for his argument, but he also knows that the premise is somewhat provocative and no one would accept it on its own terms. So, the author of the argument supports the premise with one or more claims.

We can now define an argument with a sub-argument: An argument has a sub-argument when there is at least one statement in the argument which functions both as premise and conclusion. The following diagram reflects an argument with a sub-argrument. Diagram A

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Why is Diagram A an argument with a sub-argument? It is because it has at least one statement that functions both as a premise and as a conclusion. What statement is that? It is statement 2. Statement 2 is a conclusion for statement 1, and statement 2 is a premise (along with statement 3) for statement 4. Statement 2 functions both as a premise and as a conclusion, and therefore, Diagram A displays or represents an argument with a subargument by definition.

An important question is this: How is one going to recognize an argument as having a subargument? Let’s consider the following argument: 1 (A computer cannot cheat in a game,) because 2 (cheating requires deliberately breaking rules in order to win.) 3 (A computer cannot deliberately break rules,) because 4 (a computer has no freedom of action.) If we know that this is an argument, then because of the use of the word ‘because’ in this argument, we know that 2 and 4 are premises. And, because statement 2 is found in a sentence connected to another statement (statement 1) by the use of the word ‘because,’ we know that the conclusion statement 2 is supporting is 1; the same reasoning holds for 4 in regards to 3. In terms of a diagram what we have so far is this:

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What to do now? Let’s just put these diagrams together in arbitrary ways. Diagram A

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Diagram B

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Diagram C

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Diagram D

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Let us now test these 4 diagrams. We do not have to test 2 supports 1 and 4 supports 3, because we know this is right: 2 is a premise because it is immediately preceded by ‘because’ a premise indicator (went it is found in arguments), and it is found in a sentence with another statement connected to it with the word ‘because,’ so the other statement must be what the premise is supporting; and the same reasoning holds for 4 and 3. Therefore, we have a partial check on final diagram we come up with; if it doesn’t contain 2 supports 1 and 4 supports 3, then it can’t be right. Still, how do we test these diagrams?

Let’s begin with Diagram A. We don’t have to test 2 supports 1 and 4 supports 2 for the reasons just given. But what about 1 supports 4? We do have to test this. But, how do we do it? We do that by reading the argument the way we have diagram it, and then asking the fundamental question: Does this statement support that statement? Does 1 support 4? Suppose we can’t tell on first reading. Let’s then suspend judgment and move on.

Let’s consider Diagram B. We do not have to test 2 supports 1 and 4 supports 3 for the reasons we have already given. But, what we do have to test is 3 supports 2. Let’s read it the way we have diagram it and asked the fundamental question: Does 3 support 2? Does ‘A computer cannot deliberately break rules;’ support ‘cheating requires deliberately breaking rules in order to win’? If we can recognize that 3 does not support 2 (‘A computer cannot deliberately break rules;’ is not a reason or evidence for what cheating requires.), then we can dismiss Diagram B as a candidate for best reflecting the argument.

Let’s consider Diagram C. Here again we do not have to test 2 supports 1 or 4 supports 3, we already know that this is right and we have already given our reasons. But what about 1 and 4 together supporting 3, do we have to test this? We do. Nothing up to this point has told us that 1 and 4 together supports 3. We test it by reading the argument the way we have diagramed it and asking the fundamental question: Does 1 and 4 together give any support at all to 3? Perhaps on first reading it is not clear to us. Let’s suspend judgment and move on.

Let’s consider Diagram D. Here again we have 2 supports 1 and 4 supports 3, and we do not have to test them (again, for the reasons we have already given). But we do have to test 3 and 2 together support 1. Let’s test it. We do so by reading the argument the way we have diagram it , and then asking the fundamental question: Does ‘A computer cannot deliberately break rules;’ and ‘cheating requires deliberately breaking rules;’ together support, ‘A computer cannot cheat;’? Well, if a computer cannot break rules and to break rules is to cheat, then a computer cannot do that either. Diagram D seems to be the best diagram for the argument.

Let’s return to Diagram C for a moment. 1 and 4 together do not support 3. Can you see why? There is something in the conclusion (deliberately breaking rules) not even found in the premises? ‘deliberately breaking rules’ is found in 2, but 2 supports 1, it does not support 3 in Diagram C. Diagram C contains a sub-argument. A sub-argument is an argument; 2 supports 1 is an argument. But, 1 and 4 together supports 3 is an argument too, and in this argument there is no statement 2....