Review Test Submission: Quiz 8 University of British Columbia PHIL 120 (Questions and Answers)

Review Test Submission: Quiz 4 – 2015WC-PHIL120-... H Learning Modules Module 4: Elementary Logic Review Test Submission: Quiz 4 Review Test Submission: Quiz 4 User Shu Kai Yan Course 2015WC­PHIL120­99C­Introduction to Critical Thinking­99C Jan 2016 Test Quiz 4 Started 2/8/16 10:30 PM Submitted 2/8/16 10:40 PM Due Date 2/8/16 11:59 PM Status Completed Attempt Score 47.9997 out of 54 points Time Elapsed 10 minutes out of 1 hour and 30 minutes Instructions General Instructions: Quiz 4 consists of 9 questions. You are given 1.5 hours (90 minutes) to complete the quiz. Question 1: Determine the truth value of the given propositions relating to the definition of a valid / invalid argument. Questions 2­3: Compute the truth value of the given compound propositions given the information about the truth values of their constituent parts (atomic propositions). Question 4: Using any of the truth table methods, determine whether the given arguments are valid or invalid. Questions 5­9: Translate the following statement into symbolic form, using the abbreviations provided, and match it with one of the propositions in the list. IMPORTANT: Please note that the quiz must be finished and submitted before the corresponding deadline as in the schedule, not just started ­ once the deadline is reached, the system will automatically stop the quiz and you will no longer be allowed to continue with the quiz (so you might lose your points for the quiz). Also, when you are done, make sure you press the Submit button ­ unless you do so, the quiz may not automatically be submitted to the system (and you risk losing all the points for this quiz)! If, while taking the Quiz, you experience any technical problems which prevent you from completing the Quiz, you must immediately report your issue to the IT­people responsible for the technical issues (not the instructor!) by following the "DL Help Desk" link on the main course menu. The Help Desk people monitor and record the current situation and they will then send their report to me, the instructor, with all the relevant information. If not reported to the DL Help Desk, I, the instructor, will not be able to verify any issues with the Quiz, and, as such, will not be able to change your grade or give you any other attempt to finish the quiz. My Connect Courses Library Resources Content Collection Shu Kai Yan 27 4/28/2016 Review Test Submission: Quiz 4 – 2015WC-PHIL120-... Results Displayed All Answers, Submitted Answers, Correct Answers, Feedback, Incorrectly Answered Questions Question 1 Determine whether the following propositions are True [T] or False [F]. Question Correct Match Selected Match “No invalid arguments have true conclusions.” 2. False 2. False “No valid arguments have false conclusions.” 2. False 2. False “An argument has all the premises true and the conclusion false only if it is invalid.” 1. True 1. True “An argument has all the premises and the conclusion true, if it is invalid.” 2. False 2. False “Valid arguments may preserve falsity.” 1. True 1. True All Answer Choices 1. True 2. False Response Feedback: 1. "No invalid arguments have true conclusions." – [F] Feedback: (Counter) Example: Prem. 1: Today is Monday. [May be T, may be F, depending on whether or not today is Monday. Here it doesn’t matter.] Concl.: [Therefore, it logically follows from the premise 1 that] Jupiter is the biggest planet in the Solar system. – T The conclusion here is true but this is so not due to the truth of the premise; there is no relation of logical entailment between the information in the premise and the information in the conclusion, thus invalid argument. Informally, to check whether there is logical entailment, try inserting the phrase "Therefore, it logically follows from the premise(s) that" in front of the conclusion and see whether the resulting argument sounds good. 2. "No valid arguments have false conclusions." – [F] Feedback: (Counter) Example: Prem. 1: (All) people have no less than 15 legs. – F Prem. 2: George Bush is human. – T Concl.: [Therefore, it logically follows from the premise 1 that] George Bush has no less than 15 legs. – F Though the conclusion (as well as one of the premises) is false, clearly, there is a relation of logical entailment between the premises and the conclusion, thus invalid argument. Indeed, the "Therefore, it logically follows from the premises that" test makes perfect sense; the logic cannot be blamed for the falsity of the conclusion; it 10 out of 10 points 4/28/2016 Review Test Submission: Quiz 4 – 2015WC-PHIL120-... is the falsity of the information in the premises that is responsible for the failure. (In fact, the only way when a valid argument can have a false conclusion is when not all of the premises are true, i.e., at least one of the premises is false. Good logic (i.e., using valid arguments) cannot change truth to falsity ("valid arguments preserve truth"). Yet, even perfectly good logic cannot guarantee the truth of its conclusions if it is given some false information in the premises to manipulate with.) 3. "An argument has all the premises true and the conclusion false only if it is invalid." – [T] Feedback: Whenever you have "only if" phrase, the easiest way to analyze it is to replace this expression with "therefore / then" and keep everything else (including the order of the remaining parts) intact. I.e., in our case, after the replacement we have: "An argument has all the premises true and the conclusion false THEN it is invalid." So, the part that goes after THEN is the consequent (the "THEN­part") of a bigger conditional; the part that goes in front of THEN, correspondingly, becomes the antecedent of this conditional (the "IF­part"). Adding the missing (or implied) "IF" to the first part, we get: "IF an argument has all the premises true and the conclusion false THEN it is invalid." Now it is clearly seen that it is a true proposition. Indeed, assuming you are given an argument in which all the premises are true while its conclusion is false, there is no way it can be valid (lest the truth would not be preserved). Note that the analysis of the situation would be totally different if we had mere "if" instead of "only if". This is, in fact, the next subquestion 4, below. 4. "An argument has all the premises and the conclusion true, if it is invalid." – [F] Feedback: Let's rearrange the parts of this sentence so that "IF" appears in front, and the missing (or implied) "THEN