1 / 14

Critical Reasoning Class Essay Submission and Final Exam Deadline

This is a reminder for students in the Critical Reasoning class taught by Paul Dickey, that the class essay is due today and Exercise 9-7 is to be completed. Student portfolios will also be returned. The final exam will be posted tomorrow on Quia, with some exercises that may require drawing. Next week, there will be no physical class, but students must submit the final essay and final exam by email before 11/18, 6:00 PM. Late submissions will result in grade reductions.

jillwright
Download Presentation

Critical Reasoning Class Essay Submission and Final Exam Deadline

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Philosophy 1100 Title: Critical Reasoning Instructor: Paul Dickey E-mail Address: pdickey2@mccneb.edu Website:http://mockingbird.creighton.edu/NCW/dickey.htm Today: Class Essay is due. Exercise 9-7 Student Portfolios returned. Finish Chapter 9. Tomorrow (11/12): Final Exam will be posted on Quia. There will be some exercises that may require drawing. Next week: No Physical Class. Submit Final Essay & FINAL EXAM by email BEFORE 11/18, 6:00 P.M. For every 4 hours the essay and/or exam is late, a full grade will be reduced. NO EXCEPTIONS. 1

  2. Class Workshop (Long Method) Exercise 9-7

  3. Laziness is the Mother of Invention • However there is often an easier way to demonstrate validity with truth tables. It is called the short truth-table method. • The basic principle of this method simply is to look for a row that makes the argument invalid. As soon as you find one, you are done. If you exhaust all opportunities and can’t, then the argument is valid. • Consider the argument: • P -> Q • ~Q -> R • ~P -> R • The argument could be invalid only if the conclusion is false while the premises are true. • P Q R • F T F • Thus, the argument is invalid.

  4. Now, consider the argument: • (P v Q) -> R • S -> Q • S -> R • The argument could be invalid only if the conclusion is false while the premises are true. • To make the conclusion false -- • P Q R S • F T • To make the second premise true -- • P Q R S • T F T • But there is no way now to make the first premise true, so the argument is valid.

  5. Exercises 9-8 • 1. K -> (L & G) • M -> (J & K) • B & M • B & G • To make the third premise true – • B M • T T • But to make premise 2 true • B M J K • T T T T • But to make premise 1 true, • B M J K L G • T T T T T T • But there is no way now to make the conclusion false, so the argument is valid.

  6. 2. L v (W -> S) • P v ~S • ~L -> W • P • To make the conclusion false – • P_ • F • But to make premise 2 true, • P S • F F • But to make premise 1 true, we have to introduce additional rows. There are three ways compatible with the truth-table so far, such that • L & W can be assigned so that premise 3 is true. • P S L W (W->S) • F F T T F *** • F F T F T *** • F F F F T *** • The first two of these rows makes premise 3 true, so the argument is • invalid.

  7. Class Workshop (Short Method) • Exercise 9-7 • Translation Exercise: • If Scarlet is guilty of the crime, then Ms. White must have left the back door unlocked and the colonel must have retired before ten o’clock. However, either Ms. White did not leave the back door unlocked, or the colonel did not retire before ten. Therefore, Scarlet is not guilty of the crime. • Now, is is this valid? Look at page 318 for the long proof. Wow! Now, let’s be “lazy”…

  8. Deductive Arguments:Rules of Induction

  9. Deduction: Group 1 Rules • The basic valid argument patterns of deductive logic • (If doubted, all the rules we discuss below can be confirmed by the • truth-table method) is another method to prove a deductive • argument (that is, to show that it is valid). • Modus Ponens (MP) • P -> Q • P____ • Q • -- Affirming the antecedent • P Q P->Q • T T T • T F F • F T T • F F T

  10. Deduction: Group 1 Rules • Modus Tollens (MT) • P -> Q • ~Q____ • ~P • -- Denying the consequent

  11. Deduction: Group 1 Rules • Okay, now that we have two rules to play • with, let’s stop for a minute and see how we • prove an argument valid using the rules. • (P & Q) -> R • S • S -> ~R / .’. ~ ( P&Q) • ~R 2,3, MP • ~ (P & Q) 1,4, MT

  12. Chain Argument (CA) • P -> Q • Q -> R____ • P -> R • Disjunctive Argument (DA) • P v Q P v Q • ~P ~Q__ • Q P • Simplification (SIM) • P & QP & Q • P Q • Conjunction (CONJ) • P • Q__ • P & Q

  13. Addition (ADD) • P Q • P v Q P v Q • Constructive Dilemma (CD) • P –> Q • R -> S • P v R • Q v S • Destructive Dilemma (DD) • P –> Q • R -> S • ~Q v ~S • ~P v ~R

  14. Exercises 9-10 • #1 • R -> P • Q -> R / .’. Q -> P • Q -> P 1,2, CA • #2 • P -> S • P v Q • Q -> R / .’. S v R • S v R 1,2,3, CD • #10 • (T v M) -> ~Q • (P -> Q) & (R-> S) • T / .’. ~P • T v M 3, ADD • ~ Q 1, 4, MP • P -> Q 2, SIMP • ~P 5, 6, MT

More Related