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Unformatted text preview: Ling 21: LANGUAGE & THOUGHT ARGUMENT STRUCTURE Logic: The study of arguments An argument is a sequence of statements One is the conclusion to the others. All the others are premises. The premises provide evidence for the conclusion. EXAMPLES All humans are mortal. Brad Pitt is human. Ergo, Brad Pitt is mortal. Sarah was not at the party. Ergo, it couldn't have been Sarah that Jack was dancing with. FORMAL vs INFORMAL LOGIC Formal logic: the study of argument forms abstract patterns common to many different arguments. valid If P, then Q P Ergo, Q invalid If P, then Q Q Ergo, P Informal logic: the study of particular arguments in natural language PREMISES Premises and conclusions are always propositions (statements) they can be true or false. They are not questions, commands or exclamations. Test: "It is true / not true that P" where P = a premise or a conclusion EXAMPLE
It is true that Sarah was not at the party. *It is true that Where was Sarah? *It is true that Don't you dare do that again!
Note: /*/ indicates that a statement is unacceptable. Exercise: Identifying statements. (ex. 2.1, p. 33) NOTE 1
At issue is the form of the statement, whether it CAN be true or false, not whether it IS true of false. These are PROPOSITIONS: Snow is green. I am Brad Pitt. These are NOT: *What color is snow? *Hey, look, there's Brad Pitt! NOTE 2
Although the premises, by definition, provide evidence for the conclusion, this evidence may be good or not. You have to let me go to the party; everyone is going to be there. NOTE 3 In standard form, the conclusion appears at the end. In practice, the conclusion may appear anywhere. Jack could not have been the murderer. The victim was shot from 40 feet away. Jack is blind and paralyzed from the neck down. Exercise: Identify premises and conclusions of arguments. (ex. 2.2.1, p. 37) CONCLUSIONS INDICATORES
Inference indicators: Indicate the role of a proposition in an argument. Conclusion indicators: There are no lights on. _____ no one is home. Therefore Thus Hence So For this reason Consequently It follows that Which proves/means that AS a result PREMISE INDICATORS
Premise indicators: ____ there are no lights on, no one is home. Since Because Assuming that Seeing that Granted that In view of the fact that Inasmuch as CAUTION
Conclusion and premise indicators don't always indicate conclusions and premises: *It has been ages since I ate really good sushi. *She's so cute! Exercise: Identify premise/conclusion indicators. (ex. 2.2.2, p. 37) IMPLICIT STATEMENTS
Sometimes arguments are not actually expressed or may be expressed incompletely. One of us will be cleaning the bird cage, and it won't be me. Implicit conclusion: You will be cleaning the bird cage. Alisha wears Birkenstocks, which proves that you don't have to be a tree-hugger to wear Birkenstocks. IMPLICIT ARGUMENTS Rules governing reading propositions into an argument Do so only if it is required to complete the arguer's thought. Do so only if the arguer would accept the proposition. Employ the principle of charity give the arguer the benefit of the doubt and make the argument as strong as possible. Minimize misrepresentation. NON-ARGUMENTS
1. 2. 3. 4. 5. Reports Unsupported Assertions Conditional Statements Illustrations Explanations REPORTS, ASSERTIONS Reports convey information Unsupported assertions are statements of what a speaker or writer happens to believe. CONDITIONAL STATEMENTS Conditional statements (if-then statements) Antecedent and consequent sometimes implicit: Should it rain, the picnic will be cancelled. Pete will graduate provided he passes calculus. May be parts of arguments but are not themselves arguments. ILLUSTRATIONS Illustrations: provide examples of a claim but do not prove or support it. Many wildflowers are edible. For example, daisies and day lilies are delicious in salads. There are borderline cases between examples and evidence. Many of the world's greatest musicians died at 27. for example, Jim Morrison, Janis Joplin, Jimi Hendrix and Curt Cobain. EXPLANATIONS
Explanations: try to show why something is the case, not to prove that it is the case. The Titanic sank because it hit an iceberg. (Explanation) Capital punishment should be abolished because innocent people may be mistakenly executed. (Argument) EXPLANATIONS 4 TESTS
1. The common knowledge test 1. The past-event test 1. The author's intent test 1. The Principle of Charity test COMMON KNOWLEDGE TEST
Is the explanandum (what is being explained) a matter of common knowledge? (Why would you try to prove something that is widely accepted as fact?) Many musicians die young because they `live hard.' PAST EVENT TEST
Is the explanandum an event that occurred in the past? Mel flunked because he never went to class. AUTHOR'S INTENT TEST Is the author trying ... To provide evidence for accepting the claim as true or To offer an account of why an event occurred or why something is as it is? Kevin is majoring in PoliSci because he wants to go to law school. PRINCIPLE OF CHARITY TEST
The Principle of Charity requires that we interpret unclear passages generously. Here that means not interpreting a passage as a bad argument when it would be reasonable to interpret it as a good explanation. CAUTION Not foolproof. No single shooter could have shot as quickly and as accurately as Oswald is alleged to have done in the Kennedy assassination. Therefore Oswald was not the lone shooter. Exercise: Identify arguments and explanations (ex. 2.4.1, p. 48) COMPLEX ARGUMENTS Arguments may proceed in stages. The conclusion of one set of premises may become the premise of another conclusion. All rational numbers are expressible as a ration of integers. Pi is not expressible as a ratio of integers. Ergo, Pi is not a rational number. Pi is a number. Ergo, there exists at least one non-rational number. Here the first two statements are basic premises. The third is a non-basic premise or intermediate conclusion. Exercise: Rewrite arguments in standard form Diagramming Arguments Diagrams represent inferential structure. Technique: Number all propositions. Circle all indicator words. 1 [Jane is in either New York or Paris.] But 2 [she can't be in New York] because 3 [she emailed me that she way Mark this morning], and I know 4 [Mark is in Pars. Therefore 5 [Jane must be in Paris.] 3+4 1+2 READING DIAGRAMS Read the plus signs as "together with" or "in conjunction with" Read the arrows as "is intended as evidence for" Exercise: Diagram complex arguments << IF ... THEN >>
Either ... or and if ... then statements are units. `If one batboy was found in a cave, then surely others will be found soon.' does not assert that one batboy was found or that others will be, only that if the one thing is true then the other follows. What is true or false is the asserted relationship between the two statements, not either of the statements themselves. `Either Paul is really innocent or he's a good liar.' does not assert that Paul is innocent or that he is a good liar. What is asserted is that if he's not one then he's the other. CONVERGENT ARGUMENTS
When each of the premises of an argument leads independently to the conclusion, they are not joined by plus signs. 1 [You should not shoot up.] 2 [It'll make you stupid] and 3[it'll make you poor.] 4 [It'll also break your mother's heart.] 2 3 4 1 Exercise: diagram convergent arguments ...
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