1. Analyzing Arguments 80-100: Introduction to Philosophy June 1, 2009 Instructor: Karin Howe Carnegie Mellon University

2. Statements vs. Arguments Statements are … –true or false Arguments are … –valid or invalid –sound or unsound

3. Evaluating Arguments All arguments have two different features that must be separately evaluated: form and content: The evaluation of the form of an FORMargument asks whether the conclusion follows from the premises. The evaluation of the content of CONTENTan argument asks whether all of the premises are true.

4. Recalling Definitions: Validity –A valid argument is one having the form such that it is impossible that all of its premises are true and its conclusion false. –An invalid argument is one having the form such that it is possible that all of its premises are true, and yet the conclusion is false. Soundness –An argument is sound if and only if (iff): it is valid and has all true premises. –An argument is unsound if and only if (iff): it is either invalid, or has one or more false premises.

5. Steps for Argument Analysis 1.Map the argument 2.Ask the question: sound or not?  Two Methods:  Quick-and-Dirty Method  Rigorous Method

6. Step 1: Map the Argument 1.Highlight the conclusion and subconclusion indicators 2.Highlight the premise indicators 3.Identify the conclusion (and the subconclusion(s), if there are any) 4.Identify the explicit premises 5.Break the argument down into separate statements 6.Rewrite the statements 7.Map the argument 8.(Optional) Identify any implicit premises and add them to your map  For further details, see the slides from May 19th.

7. Step 2: Sound or not? To show an argument is unsound: –Show that either some or all of the premises are (likely) not true, or that the argument is invalid. To show an argument is sound: –Show that the argument is both valid AND all the premises are (likely) true.

8. Two Methods: Quick-and-Dirty Method Rigorous Method

9. Quick-and-Dirty Method Pick whichever aspect (boxes or arrows) seems easiest to critique, and do that. It's that easy!! Note: If the aspect that you look at first turns out to be fine, then you must default to the rigorous method.

10. Rigorous Method Look at form (validity) –Showing validity: Valid forms (see handout) Using the definition of validity –Showing invalidity: Invalid Forms (see handout) Using the definition of invalidity Look at content (truth of the premises)

11. Advantages of the Rigorous Method If an argument is sound, then the rigorous method is the ONLY way to show this. If an argument is unsound because of content (untrue premises) only, then you will look really fair-minded by granting the validity of the argument, even if the argument fails because some or all of the premises are false. Most importantly, however, you will have taken those false premises off the table for future arguments. If an argument is unsound because of validity only, then you will again look fair-minded by acknowledging the truth of the premises, even if the argument fails because of its logical structure. If an argument is unsound because it fails on both counts, then you’ve proven it (sort of) doubly unsound, and you can now go neener neener neener.

12. Bottom Line Some important things to keep in mind when analyzing arguments: –Be fair-minded and charitable. –Be clear about what you are objecting to (box or arrow) - don’t leave your reader guessing. –Use clear, unambiguous language to articulate your objections. Use technical vocabulary correctly in order to not distract or confuse your reader. –If you are objecting by making a counter-claim, make sure you provide more support for your claim than the author does for his or her claim. –Objecting to a missing premise is (generally) a fairly weak objection. –If you think that the form is good (valid) but there is something “fishy” about the conclusion, then there must be something that you object to in the content of the premises (by the definition of validity!). Note that you can have a valid argument with false premises and a false conclusion - that’s no problem (at least from the point of view of questions about validity). Think kangaroos! –At the end of the day - don’t leave your reader guessing!! Was the argument sound... or not?!

13. Last but not least… Have fun!!