Text Table of Contents #5: Evaluating the Argument

 Arguments intend to convince us to accept a conclusion – i.e., a position, claim, belief, etc.  Why does the author want us to accept this conclusion?  The reasons tell us why that conclusion should be accepted.  Accepting the conclusion based on the reasons is reasoning.  But there are some presumptions we need to make in order to accept the reasoning.

 Are the reasons true?  Is the logical connection between the reason and conclusion strong? ◦ The conclusion must be true or probably true if the reason is true.  Are the reasons relevant to the conclusion? ◦ Truth of conclusion depends on the reason.  Circularity - the reason can’t depend on the conclusion ◦ Can’t say “the reason because of the conclusion.”

 Infer  deduce or conclude (information) from evidence and reasoning rather than from explicit statements (Oxford dictionary)  Strength of Logic = Validity of Inference ◦ does not refer to truth of premise or conclusion ◦ refers to the form of the inference ◦ i.e., how the inference is drawn  A word about inference - induction vs. deduction  induction – results in probable conclusion  deduction results in certain conclusion

 All fruits are sweet.  A banana is a fruit.  Therefore, a banana is sweet.  For the conclusion to be necessarily true, the premises need to be true.  Strong Logic ◦ The conclusion is true or probable if the reasons are true. ◦ Ask yourself: Could the conclusion be wrong if the reasons are true?

 R1. When a muffler gets old the baffles loosen.  R2. Loose muffler baffles often rattle when idling.  R3. My muffler is old.  R4. A rattling noise is coming from underneath my car in the back or middle area when idling.  Conclusion: ◦ The rattling sound is coming from my muffler. ◦ Could the rattling not be coming from the muffler even if the reasons are all true? ◦ Could anything else be explained by the reasons?

 State data show that average state funding for colleges has shrunk by 20-30% in the last five years.  Based on recent alcohol industry data, selling alcohol on campus has increased revenues by several percentage points for colleges that permit on-campus alcoholic beverage consumption.  Conclusion: ◦ Colleges can offset reduced state funding by permitting alcohol consumption in college-operated on-campus venues.

 Leading from true premises to a false conclusion.  All apples are fruit. (correct)  Bananas are fruit. (correct)  Therefore, bananas are apples. (incorrect)  Weak Logic ◦ The reasons are true ◦ But the conclusion does not follow

 Students who served in the military deserve a beer.  It (alcohol consumption on campus) will create a more diverse environment on campus.  Conclusion: ◦ College students should be able to consume liquor.

 Logical strength is: ◦ Does the conclusion have to be true (or probable) if the reason(s) is(are) true?  Relevance is: ◦ Do the reasons have to be true for the conclusion to be true?  In the muffler example assume that the car has nothing else in the area described that could come loose and rattle.

 R1. When a muffler gets old the baffles loosen.  R2. Loose muffler baffles often rattle when idling.  R3. My muffler is old.  R4. A rattling noise is coming from underneath my car in the back or middle area when idling.  Conclusion: ◦ The rattling sound is coming from my muffler. ◦ Could the muffler be rattling and it not be broken baffles? ◦ Got the right conclusion – but has nothing to do with reasons.

 When the conclusion serves to support a reason. ◦ Typically the conclusion is contained in a single assumption.  Most obvious circularity when the conclusion is simply another way of stating (or very similar to) the reason. ◦ R1. I am an A student. ◦ Concl: You can’t give me a C. ◦ Another way of stating the argument is: You can’t give me a C because I am not a C student. ◦ R1. There is a law against stealing. ◦ Concl: Therefore stealing is wrong. ◦ We wouldn’t make something illegal if it’s “right” would we?