Other Info on Making Arguments

1. Other Info on Making Arguments Deductive vs. Inductive Sound vs. Unsound Cogent vs. Uncogent Valid vs. Invalid

2. Deductive vs. Inductive

3. To distinguish the difference… • Look for special indicator words. • Address the actual strength of the link between the premises and conclusion.

4. Indicator Words

5. To determine the link… • This is the “actual strength” of the link between the premises and the conclusion. • This does not require indicator words • Deductive: the conclusion does, in fact, follow necessarily, from the premises • Inductive: if the conclusion does not necessarily follow the premises, but it does follow probably, then apart from other criteria, the argument is inductive

6. Valid Arguments • This is determined by form. A = B B = C A = C If terms are uniformly substituted in place of the letters, it can still be valid. This is called “substitution instance of the form”.

7. Invalid Arguments • Not every set of terms result in an argument having two premises and a false conclusion – but it is always possible to find terms that give this result. • INVALID = true premises, false conclusion A = B C = B A = C

8. Random Note • The word “some” in logic means “at least one” • You’ll have to watch the language within arguments more than anything. People use charged words to confuse and mislead.

9. Sound vs. Unsound • Sound = if the argument is valid and all premises are true SOUND = VALID + ALL TRUE PREMISES All cats are mammals. All mammals are animals. ---------------------------------- All cats are animals. SOUND

10. Sound vs. Unsound • Unsound = the argument is invalid (or) has one or more false premises (or both) All cats are mammals. All cats are animals. ---------------------------------- All mammals are animals. UNSOUND

11. Sound Arguments • Good deductive argument: True premises Good reasoning Therefore, true conclusion

12. To evaluate sound.. • Check for validity. • If valid, check to ensure that all premises are true.

13. Strong vs. Weak • Strong = Inductive arguments • It is improbable that the premises be true and the conclusion false. • It’s an assumed truth, based on that assumption, it is probable that the conclusion is true. All previously discovered emeralds have been green. Therefore, probably the next emerald to be discovered will be green. STRONG

14. Degrees of Strength with Probability • If the probability is more than 50% likely, it is a STRONG argument. • If the probability is less than 50%, it is a WEAK argument. • Determine the relationship between premises and conclusion, not by truth or falsity of the premise.

15. Cogent vs. Uncogent • Cogent = strong + all true premises (inductive) • Cogent = True premises Good reasoning Therefore, probably true conclusion • Uncogent = is weak or has one or more false premises (if either is missing, it is uncogent)

16. Apply this in your own writing… • This is not formulaic writing. • It’s all common sense, which relies on you doing simple math to ensure that one point leads smoothly to the next point. But more importantly, the idea is that you show and prove a logical and accurate point is made.