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2 Day 1Intro Day 2Chapter 1 Day 3Chapter 2 Day 4Chapter 3 Day 5Chapter 4 Day 6Chapter 4 Day 7Chapter 4 Day 8EXAM #1 40% of Exam 1 60% of Exam 1 warm-up
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4 science of reasoning Logic is the science of reasoning, which is to say: the academic discipline that investigates reasoning.
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5 reasoning is inferring (deducing) to infer is to draw conclusions (output) from premises (input).
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6 words/ideas related to ‘draw’ both words mean to pull an often used cognate of ‘draw’ is ‘draft’ (‘draught’)
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8 You see smoke, (input) and you infer (deduce) that there is fire. (output) You count 19 in a group, (input) which originally had 20,(input) and you infer (deduce) that someone is missing.(output)
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9 arguments Logic evaluates reasoning in terms of arguments.
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10 ar·gu·ment (är “ gy … -m … nt) n. 1.a. A discussion in which disagreement is expressed; a debate. b. A quarrel; a dispute. c. Archaic. A reason or matter for dispute or contention: “sheath'd their swords for lack of argument” (Shakespeare). 2.a. A course of reasoning aimed at demonstrating truth or falsehood: presented a careful argument for extraterrestrial life. b. A fact or statement put forth as proof or evidence; a reason: The current low mortgage rates are an argument for buying a house now. 3.a. A summary or short statement of the plot or subject of a literary work. b. A topic; a subject: “You and love are still my argument” (Shakespeare). 4. Logic. The minor premise in a syllogism. 5. Mathematics. a. The independent variable of a function. b. The amplitude of a complex number. 6. Computer Science. A value used to evaluate a procedure or subroutine. [Middle English, from Old French, from Latin arg ¿ mentum, from arguere, to make clear. See ARGUE.] [American Heritage Dictionary]
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11 argument an argument is a collection of statements, one of which is designated as the conclusion, and the remainder of which are designated as the premises.
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12 statement A statement is a declarative sentence, i.e., a sentence that is capable of being true or false. Kinds of sentence declarative interrogative imperative exclamatory performative Example the window is shut is the window shut? shut the window $%&@!!!! I hereby …
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13 there is smoke(premise) therefore, there is fire (conclusion) there are 19 persons currently(premise 1) there were 20 persons originally (premise 2) therefore, someone is missing(conclusion)
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14 1.are all the premises true? 2.does the conclusion follow from the premises? 1.do the premises rest on the facts? 2.does the conclusion rest on the premises? Alternatively,
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16 it is both factually correct and valid. sound its conclusion follows from its premises valid all its premises are truefactually correct if and only ifan argument is
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17 therefore McHale is taller than Bird Parish is taller than McHale Parish is taller than Bird
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19 Example 1 YESsound? YESvalid? YESfactually correct? T / Parish is taller than Bird T McHale is taller than Bird T Parish is taller than McHale
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20 Example 2 NOsound? YESvalid? NOfactually correct? F / Bird is taller than Parish F McHale is taller than Parish F Bird is taller than McHale
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21 Example 3 NOsound? NOvalid? YESfactually correct? T / McHale is taller than Bird T Parish is taller than Bird T Parish is taller than McHale
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22 Example 4 NOsound? NOvalid? NOfactually correct? F / Bird is taller than Parish F McHale is taller than Bird F McHale is taller than Parish
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23 Whether an argument is valid or invalid is determined entirely by its form. validity is a function of form
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24 If an argument is valid, then every argument with the same form is also valid. If an argument is invalid, then every argument with the same form is also invalid.
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25 In order to show that an argument is invalid, counterexample it is sufficient to find a counterexample to it.
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26 Consider an argument; call it . counterexample Then a counterexample to is (by definition) any argument * with the following properties: same form 1. * has the same form as ; true premises 2. * has all true premises; false conclusion 3. * has a false conclusion.
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27 Argument is taller than Parish is taller than McHale is taller than Parish is taller than Bird is taller than / McHale is taller than Bird T T T T T F Form is taller than is taller than is taller than X is taller than Y X is taller than Z / Y is taller than Z Counterexample is tallerthan The Library is taller than PeeWee Herman is taller than The Library is taller than Arnold Swarzenegger is taller than / PeeWee H. is taller than Arnold S.
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29 Argument allare all UMass students are high school graduates someare some high school graduates are athletes someare / some UMass students are athletes T T T T T F allare someare someare Form all X are Y some Y are Z / some X are Z Counterexample allare all UMass students are high school graduates someare some high school graduates are U.S. senators someare / some UMass students are U.S. senators
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