Douglas Walton Assumption University Chair in Argumentation Studies

1. Elements and Methods of Argumentation TheoryUniversity of Padua Lecture Padua, Italy, Dec.1, 2008. Douglas Walton Assumption University Chair in Argumentation Studies Centre for Research in Reasoning, Argumentation & Rhetoric (CRRAR) University of Windsor

2. What is an Argument? • An argument is a social and verbal means of trying to resolve, or at least contend with, a conflict or difference that has arisen between two parties engaged in a dialog by eliciting reasons on both sides (Walton, 2007). • According to this definition, an argument necessarily involves a claim that is advanced by one of the parties, typically a claim that the one party has put forward as true, and that the other party questions. • Arguments have premises and conclusions, they can be of different kinds, they can be stronger or weaker (have weights), and different standards of proof can be required of them in different contexts of use.

3. Deductive Argument • Premise: Luigi is an Italian soccer player. • Premise: All Italian soccer players are divers. • Conclusion: Luigi is a diver. • It is logically impossible for the premises to be true and the conclusion false. • But is the first premise true?

4. Inductive Argument • Premise: Luigi is an Italian soccer player. • Premise: Most Italian soccer players are divers. • Conclusion: Probably Luigi is a diver. • It is improbable for the premises to be true and the conclusion false.

5. Deductive, Inductive, and the 3rd Type: Abductive? Wigmore (1931, p. 20) considered arguments of a kind that are commonly used in collecting evidence in law. Last week the witness A had a quarrel with the defendant B, therefore A is probably biased against B. A was found with a bloody knife in B’s house, therefore A is probably the murderer of B. Clue: Backward Reasoning by Explanation?

6. Defeasible Reasoning • Birds fly. • Tweety is a bird. • Therefore Tweety flies. • Subject to exceptions (Tweety = penguin). • Based on non-absolute generalizations. • Nonmonotonic: valid arguments can become invalid by adding premises.

7. Defeasible Linked Argument

8. Typical Argumentation Schemes • Common schemes include such familiar types of argumentation as argument from lack of knowledge, argument from example, argument from a rule to a case, argument from a verbal classification, argument from position to know, argument from expert opinion, argument from analogy, argument from precedent, argument from correlation to cause, practical reasoning, abductive reasoning, argument from gradualism, and the slippery slope argument. • Other schemes that have been studied include argument from waste (also called sunk costs argument), argument from temporal persistence and argument from appearance. • In addition to presumptive schemes, it is possible to treat deductive and inductive forms of argument as schemes. • All are linked arguments.

9. Argument from Expert Opinion • Dr. Phil is an expert in psychology. • Dr. Phil says that Bob has low self-esteem. • Therefore Bob has low self-esteem.

10. Scheme: Arg. from Expert Opinion • Major Premise: Source E is an expert in domain D containing proposition A. • Minor Premise:E asserts that proposition A (in domain D) is true (false). • Conclusion:A may plausibly be taken to be true (false).

11. Araucaria • Araucaria is a software tool for analyzing arguments. It aids a user in reconstructing and diagramming an argument using a simple point-and-click interface. The software also supports argumentation schemes, and provides a user-customizable set of schemes with which to analyze arguments. • Once arguments have been analyzed they can be saved in a portable format called AML, the Argument Markup Language. • http://www.computing.dundee.ac.uk/staff/creed/araucaria/

12. Dr. Phil Argument Diagram

13. Corroborative Expert Opinions

14. Questionable Example • This alarming defense spending will lead to economic disaster. According to Einstein, heavy defence spending in a country is a sign of political instability that is not consistent with sound fiscal policies that can yield lasting financial recovery from a recession. • Einstein is cited as an expert. • But is he an expert in the right field for the argument? • Fallacy of argument from authority.

15. Critical Questions for Scheme • Expertise Question: How knowledgeable is E as an expert source? • Field Question: Is E an expert in the field D that A is in? • Opinion Question: What did E assert that implies A? • Trustworthiness Question: Is E personally reliable as a source? • Consistency Question: Is A consistent with what other experts assert? • Backup Evidence Question: Is E’s assertion based on evidence?

16. Screen Shot of Dr. Phil

17. Enthymemes • An enthymeme is an argument with an implicit premise or conclusion. • All physicians are college graduates, so all members of the AMA are college graduates. • MISSING PREMISE: All members of the AMA are physicians. • Roadside sign: “The bigger the burger, the better the burger. The burgers are bigger at Burger King.” • MISSING CONCLUSION: The burgers are better at Burger King.

18. Argument with Missing Premises • This example was found on a web site called animal freedom. • Animals in captivity are freer than in nature because there are no natural predators to kill them. • Conclusion: animals in captivity are freer than in nature. • Explicit Premise: there are no natural predators to kill animals that are in captivity. • Implicit Premise: there are natural predators to kill animals that are in nature. • Implicit Premise: if animals are in a place where there are no natural predators to kill them, they are freer than if they are in a place where there are natural predators to kill them.

19. Common Knowledge & Commitment

20. How Arguments are Evaluated • Burdens of proof and standards of proof, along with argument weights, determine how to evaluate the argumentation in a dialog. • The burden and standard of proof are set at the opening stage, and depend on the type of dialog. • In the argumentation stage, each side presents reasons supporting its view and attacks the opposed view by raising critical questions and rebuttals. • The burdens and standards are then applied at the closing stage to determine which side won and which lost the dialog.

21. Some Further Reading • Douglas Walton, ‘The Three Bases for the Enthymeme: A Dialogical Theory’, Journal of Applied Logic, 6, 2008, 361-379. • Douglas Walton, Fundamentals of Critical Argumentation, Cambridge, Cambridge University Press, 2008. • Douglas Walton, Chris Reed and Fabrizio Macagno, Argumentation Schemes, Cambridge, Cambridge University Press, 2008.