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Lecture 9: Analyzing Arguments – Diagramming Short Arguments.

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Presentation on theme: "Lecture 9: Analyzing Arguments – Diagramming Short Arguments."— Presentation transcript:

1 Lecture 9: Analyzing Arguments – Diagramming Short Arguments

2 This is a bit of historical documentation of what Spring Breaks were like when I was an undergraduate (well, really when I was still in high school) …. Welcome Back from Spring Break

3 Today: Analyzing Arguments But first, a fallacy in the news … Can you spot it? What kind of fallacy is this? What Obama said re. Trayvon Martin What Gingrich said Obama said re. Trayvon Martin What Gingrich said Obama said re. Trayvon Martin

4 Arguments – Review Arguments consist of premises and conclusions. Premises and conclusions are statements.

5 Arguments – Review Premise indicator words: since, because, for, given that, seeing that, considering that, inasmuch as, as, in view of the fact that, as indicated by, judging from, on account of Conclusion indicator words: therefore, thus, hence, consequently, so, accordingly, it follows that, for this reason, that is why, which shows that, wherefore, this implies that, as a result, this suggests that, this being so, we may infer that.

6 Diagramming Short Arguments Argument: The death penalty should be abolished because it’s racially discriminatory, there’s no evidence that it’s a more effective deterrent than life imprisonment, and innocent people may be executed by mistake.

7 Diagramming Short Arguments Step 1: Identify (circle, underline, etc.) all premise and / or conclusion indicators. The death penalty should be abolished because it’s racially discriminatory, there’s no evidence that it’s a more effective deterrent than life imprisonment, and innocent people may be executed by mistake.

8 Diagramming Short Arguments Step 2: Number the statements consecutively as they appear in the argument. 1)The death penalty should be abolished 2)because it’s racially discriminatory, 3)there’s no evidence that it’s a more effective deterrent than life imprisonment, and 4)innocent people may be executed by mistake.

9 Diagramming Short Arguments Step 3: Arrange the numbers on a page with the premises placed above the conclusion(s) they claim to support. 2)3)4) 1)

10 Diagramming Short Arguments Step 4: Omit any logically irrelevant statements. Step 5: Use arrows to mean ‘is offered as evidence for’ to show relationship of argument support. 2)3)4) 1) Here 2), 3), and 4) offer independent support for the conclusion.

11 Diagramming Short Arguments A premise provides independent support for a conclusion when the amount of support it provides would not be weakened or destroyed by the removal of any other premise in the argument. A premise provides linked support when it works conjointly with another premise to support the conclusion: EXAMPLE: No member of the SJSU community is a fan of the Leland Stanford Junior University Marching Band. Maurice is a member of the SJSU community. So, Maurice is not a fan of the Leland Stanford Junior University Marching Band.

12 Diagramming Short Arguments – Linked Support 1)No members of the SJSU community is a fan of the Leland Stanford Junior University Marching Band. 2)Maurice is a member of SJSU community. 3)So, Maurice is not a fan of the Leland Stanford Junior University Marching Band.

13 Diagramming Short Arguments Linked Support: 1) +2) 3)

14 Linked or Independent Support? Linked: Omission of one premise cancels / reduces support provided by the other. Example: No student in Ling 21 is a Rhodes Scholar. Josue is a Rhodes Scholar. So, Josue is not a student in Ling 21. Independent: Neither premise would provide less support for the conclusion if the other were omitted. Example: Nick doesn’t own a car. Nick is legally blind. So Nick probably won’t drive a car to the game.

15 Linked or Independent Support? Ten witnesses say they saw Blotto rob the bank. The stolen bank money was found in Blotto’s car. Blotto’s fingerprints were found at the Teller’s window. Therefore, Blotto probably robbed the bank. If Amy runs marathons, then she’s probably very fit. Amy does run marathons. So Amy probably is very fit.

16 Other Kinds of Support 1)Jim is a senior citizen. 2)So, Jim probably doesn’t like hip-hop music. 3)So, Jim probably won’t be going to the Ashanti concert tonight. 1) 2) 3)

17 Other Kinds of Support Example: Most Democrats are liberals, and Senator Dumdiddle is a Democrat. Thus, Senator Dumdidle is probably a liberal. Therefore, Senator Dumdiddle probably supports affirmative action in higher education, because most liberals support affirmative action in higher education.

18 Other Kinds of Support Example: 1)Most Democrats are liberals, and 2)Senator Dumdiddle is a Democrat. 3)Thus, Senator Dumdidle is probably a liberal. 4)Therefore, Senator Dumdiddle probably supports affirmative action in higher education, 5)because most liberals support affirmative action in higher education.

19 Other Kinds of Support Premises and conclusions: 1)+2) 3)+5) 4)

20 Other Kinds of Support Cheating is wrong for several reasons. First, it will lower your self-respect, because you can never be proud of anything you got by cheating. Second, cheating is a lie because it deceives other people into thinking you know more than you do. Third, cheating violates the teacher’s trust that you will do your own work. Fourth, cheating is unfair to all the people who aren’t cheating. Finally, if you cheat in school now, you’ll find it easier to cheat in other situations later in life – perhaps even in your closest personal relationships.

21 Other Kinds of Support 1) Cheating is wrong for several reasons. 2) First, it will lower your self-respect, 3) because you can never be proud of anything you got by cheating. 4) Second, cheating is a lie 5) because it deceives other people into thinking you know more than you do. 6) Third, cheating violates the teacher’s trust that you will do your own work. 7) Fourth, cheating is unfair to all the people who aren’t cheating. 8) Finally, if you cheat in school now, you’ll find it easier to cheat in other situations later in life – perhaps even in your closest personal relationships.

22 Other Kinds of Support Notice the use of because in 3) and 5): 3)5) 2)4)

23 Other Kinds of Support Note that 2), 4), 6), 7), and 8) all provide independent support for the main conclusion 1): 3)5) 2)4)6)7)8) 1)

24 Tips on Diagramming Short Arguments Find the main conclusion first Pay close attention to premise and conclusion indicators. Remember: sentences containing the word ‘and’ often contain two or more separate statements. Treat conditional statements (if-then) and disjunctive statements (either-or) as single statements. Don’t number / diagram any sentence that is not a statement. Don’t diagram irrelevant statements. Don’t diagram redundant statements.

25 Practice Critical Thinking, p , Exercise 7.1 Step 1: Identify (circle, underline, etc.) all premise and / or conclusion indicators. Step 2: Number the statements consecutively as they appear in the argument. Step 3: Arrange the numbers on a page with the premises placed above the conclusion(s) they claim to support. Step 4: Omit any logically irrelevant statements. Step 5: Use arrows to mean ‘is offered as evidence for’ to show relationship of argument support.


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