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Effective Argumentation Prof. R. Cherubin

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Effective Argumentation Prof. R. Cherubin

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    1. Effective Argumentation Prof. R. Cherubin

    3. Evidence is only the beginning For an argument to be effective, in the sense used in this course, you must do more than present the information that you take to be evidence for the truth or validity of your conclusion. You also need to show how – by what reasoning – that evidence makes your conclusion true or valid.

    4. Evidence is only the beginning Even valid evidence can be used ineffectively or deceptively to reach unsupported or incorrect conclusions. Therefore correct and adequate reasoning is also part of effective argument.

    5. How to Argue Well – And How Not To Do It Ineffective or incorrect arguments can appear in your sources. Do not be lulled into trusting everything a distinguished author says, just because he or she is distinguished or presents things in an impressive manner. It’s also possible that you may develop an ineffective or incorrect argument concerning the data you have gathered. This lecture will show you some common problems, and how to detect and avoid them. If an author is worthy of distinction, he or she will show you how he or she reached the conclusions you are reading, and why those are appropriate and warranted conclusions to reach.If an author is worthy of distinction, he or she will show you how he or she reached the conclusions you are reading, and why those are appropriate and warranted conclusions to reach.

    6. The Logical Fallacy “Post Hoc Ergo Propter Hoc” (“After this, therefore because of this”) A “post hoc ergo propter hoc” argument asserts that since event A happened (or always happens) before event B, A must cause B. While it may be true that A is the cause of B, it also may not be true. In any case, the fact that A happened (or always happens) before B does not BY ITSELF show that A is a cause of B. More information and reasoning are needed to show whether A causes B.

    7. The Logical Fallacy “Post Hoc Ergo Propter Hoc” (“After this, therefore because of this”) Example: “Global temperatures have risen since the founding of McDonald’s® restaurants. Therefore McDonald’s is a cause of temperature change.” Is it true that McDonald’s causes temperature change? -- Perhaps, perhaps not. Is the argument above enough to show that McDonald’s causes temperature change? –No. – What other evidence and reasoning are needed? Other evidence and reasoning needed: showing that something that McDonald’s does, or something that McDonald’s requires, affects climate. Probably the connection would involve several steps – for example, showing that McDonald’s requires vast amounts of beef that would not otherwise be needed or that is farmed in a way unique to McDonald’s and that this cattle farming does something (produces methane, or requires deforestation) which in turn can by means of demonstrable and repeatable experiments be shown to affect the atmosphere in a way that brings about (not merely correlates with) climate change.Other evidence and reasoning needed: showing that something that McDonald’s does, or something that McDonald’s requires, affects climate. Probably the connection would involve several steps – for example, showing that McDonald’s requires vast amounts of beef that would not otherwise be needed or that is farmed in a way unique to McDonald’s and that this cattle farming does something (produces methane, or requires deforestation) which in turn can by means of demonstrable and repeatable experiments be shown to affect the atmosphere in a way that brings about (not merely correlates with) climate change.

    8. The Logical Fallacy “Cum Hoc Ergo Propter Hoc” (“With this, therefore because of this”) A cum hoc ergo propter hoc argument claims that since A and B occurred together, A must cause B. (A variant of this fallacy suggests that if A and B occur together every time they are observed, then they must occur together.) While it may be true that A caused B, it may instead be true that B caused A. Or it may be the case that neither of them caused the other. It may be the case that they occurred together by coincidence, or because of some third factor that the arguer has not identified.

    9. The Logical Fallacy “Affirming the Consequent” This is conceptually related to the previous two, but covers in addition arguments that do not involve temporal relationships. An argument that “affirms the consequent” begins with a statement of the form “If A, then B.” It then produces evidence that B is the case. From that, it concludes that A is the case. As before, it may in fact be true that A is the case. But more is needed to show that it is true.

    10. The Logical Fallacy “Affirming the Consequent” Example 1: “It is raining, therefore the streets are wet.” (If it is raining (A), then the streets are wet (B).) “The streets are wet.” (B) “Therefore it is raining.” (Therefore A) What’s wrong with this?

    11. The Logical Fallacy “Affirming the Consequent” (this image comes from cpgis.gmu.edu)

    12. The Logical Fallacy “Affirming the Consequent” Example 2: “If an animal is moving its tail (A), then the animal is alive (B).” “The animal is alive.” (B) “Therefore it is moving its tail.” (Therefore A) What’s wrong with this chain of reasoning?

    13. The Logical Fallacy “Affirming the Consequent” Thus in general, when you have an “if-then” statement and the consequent (the “then” part) is true, that does not BY ITSELF make the antecedent (the “if” part) true. If you want to show that the antecedent is true, you need to find more evidence and show how that evidence makes the antecedent true.

    14. Logical Fallacy “Circular Reasoning” “Circular” arguments look as though they are proving something, but on closer inspection one finds that they are simply repeating something without proving it. The antecedent (the “if” part) is actually the same as the consequent (the “then” part, or the “therefore” part). One common kind of circular argument is known as “begging the question” (i.e. begging off from the question, avoiding a question). In this kind of argument, something questionable is assumed to be true, and the conclusion of the argument simply repeats this assumption without supporting it.

    15. Logical Fallacy “Circular Reasoning” Example 1: “The SAT is a good indicator of intelligence. Intelligence varies directly with test scores.” “Therefore the students who do well on the SAT are more intelligent than those who do not.” What’s wrong with this reasoning? - It may be that high SAT scores correlate with higher intelligence (whatever that is) and lower scores with lower intelligence. But the argument does not show that; it simply repeats the (questionable) claim that higher intelligence correlates with high SAT scores. Even if the correlation were verifiable, it still would not be enough to prove a causal relationship (such that every high-scoring student would be more intelligent than those with lower scores).- It may be that high SAT scores correlate with higher intelligence (whatever that is) and lower scores with lower intelligence. But the argument does not show that; it simply repeats the (questionable) claim that higher intelligence correlates with high SAT scores. Even if the correlation were verifiable, it still would not be enough to prove a causal relationship (such that every high-scoring student would be more intelligent than those with lower scores).

    16. Logical Fallacy “Circular Reasoning” Example 2: “There is conservation of matter and energy.” “No thing can come from nothing.” “There has been no thing or process that lacked a predecessor, and there has been no thing or process that disappeared leaving nothing behind.” “Therefore the sum of matter and energy in the universe remains, and always will remain, the same.” - What’s wrong with this reasoning? – Note that the second, third, and fourth steps really echo the first step in one way or another; and the fourth step is simply a restatement of the first. – Note also that the poor quality of the argument does not mean that there is NOT conservation of matter and energy (though if there isn’t...you heard it here first).

    17. “Fallacy of Composition” “Fallacy of Division” In the fallacy of composition one assumes that if the parts of a thing have a certain quality or attribute, then the whole thing (that of which the parts are parts) has that quality or attribute too. In the fallacy of division one assumes that if a thing as a whole has a certain quality or attribute, then its parts (or a specific part of it) has that quality or attribute too.

    18. “Fallacy of Composition” “Fallacy of Division” Example 1 (“composition”) “No state, territory, or protectorate in the U.S. can grant passports to citizens. Therefore the U.S. cannot grant passports to its citizens.” Example 2 (“division”) “A healthy cat can play with string. Therefore its appendix can play with string.”

    19. “Fallacy of Composition” “Fallacy of Division” There are of course cases where the whole and its parts do have characteristics in common. For example, if every square inch of a car’s exterior is red, then the whole of the car’s exterior is red. And if one part of a person’s body has a certain DNA sequence, the person’s whole body has that sequence.

    20. “Fallacy of Composition” “Fallacy of Division” But the difference between committing the fallacy of composition or the fallacy of division on the one hand, and making a true statement about the relationship between a whole and its parts on the other, is this: In the fallacies, one assumes that because the whole has a characteristic, the part must have it, or vice-versa, without investigating whether the characteristic in question is one that must be shared by part and whole.

    21. Argumentative Fallacy “False Dichotomy” An argument commits the fallacy of false dichotomy when it suggests falsely that there are only two possibilities in a given situation, and then claims that if one of the two is not fulfilled, the other must be. Sometimes the assumption that only two possibilities exist is not made explicit, but it becomes clear from the way the argument proceeds.

    22. Argumentative Fallacy “False Dichotomy” Example 1: “Everyone in this country is either a Democrat or a Republican.” “Senator Jeffords is not a Republican.” “Therefore he is a Democrat.” What’s wrong with this? Senator Jeffords is listed as an Independent. He was first elected as a Republican, but left the party. It is a false dichotomy to suggest that Democrat and Republican are the only possible political parties (or positions) in this country. Senator Jeffords is listed as an Independent. He was first elected as a Republican, but left the party. It is a false dichotomy to suggest that Democrat and Republican are the only possible political parties (or positions) in this country.

    23. Argumentative Fallacy “False Dichotomy” Example 2: According to Plato, Socrates was accused of atheism by someone who argued in the following way: “Socrates does not believe in the gods of Athens, therefore he is an atheist.” Leaving aside the question of whether Socrates actually believed in the gods of Athens, it’s clear that his accuser assumed...

    24. Argumentative Fallacy “False Dichotomy” ...that the gods of Athens are the only gods, so that one who does not believe in them does not believe in any gods. In assessing others’ arguments, and in constructing your own, take time to ask whether there are alternative possibilities that have not been considered.

    25. Logical Fallacy “Undistributed Middle” An argument commits the fallacy of undistributed middle if it claims falsely that because all A’s are B’s and all C’s are B’s, all A’s are C’s. (Or: because all A’s are B’s and person C is a B, person C is an A.) Example 1: “All wombats are marsupials.” “All sugar gliders are marsupials.” “Therefore all wombats are sugar gliders.”

    26. Logical Fallacy “Undistributed Middle” Example 2: “All atheists support the separation of church and state.” “George Mason supported the separation of church and state.” “Therefore George Mason was an atheist.” What’s wrong with this inference?

    27. Logical Fallacy “Undistributed Middle” “That religion, or the duty which we owe to our Creator and the manner of discharging it, can be directed by reason and conviction, not by force or violence; and therefore, all men are equally entitled to the free exercise of religion, according to the dictates of conscience; and that it is the mutual duty of all to practice Christian forbearance, love, and charity towards each other.” George Mason, Virginia Declaration of Rights, Article XVI. In other words, George Mason was not an atheist, but strongly supported separation of church and state.In other words, George Mason was not an atheist, but strongly supported separation of church and state.

    28. Argumentative Fallacy “Argument from Authority” An argument from authority claims that the reader should accept something just because a person who is distinguished or accomplished or experienced (in a relevant field, or, in the more egregious cases, in any field) says it is true. But if the purported authority really is credible in this case, he or she (or the author citing him or her) will provide the reasoning and evidence to show why his or her claims are correct.

    29. Argumentative Fallacy “Argument from Authority” Remember, the fact that someone has a Ph.D., even from a great institution, does not mean that everything that he or she writes reflects the standards of research that merited the Ph.D. Or, perhaps there is some research of which he or she is unaware. Or perhaps the piece you are reading was written some time ago, and later research showed flaws in what you are reading.

    30. Then if a writer commits a fallacy or if for some other reason we don’t know whether what he or she says is true, should we conclude that what he or she says is false? For example, if a writer claims that a new sub-species of capybara has been discovered, but does not show that the new sub-species is any different from the ones already known, should we conclude that the new kind of capybara does not exist?

    31. Known capybaras – from the Phoenix Zoo www.phoenixzoo.org/images/animals/capybara.jpg

    32. No – that’s the fallacy of Argument from Ignorance. In an argument from ignorance, a writer falsely assumes that since we do not know that something is true, or that something exists, we are justified in concluding that it is not true. But in fact, absence of evidence is not evidence of absence. The fact that we have not seen evidence of the new kind of capybaras does not mean that they do not exist – and it does not mean that they do exist. It means we do not have enough information to tell.

    33. Tips for Arguing Well Become aware of your starting assumptions, and the starting assumptions of the authors you are reading. Ask yourself whether these assumptions are true; if you don’t know, try to find out. If you can’t find out, consider that the author’s arguments will be at best conditionally true: true if the assumptions are true. Examine all arguments and explanations – your own and the ones you read. Can you see how the conclusions follow from the starting-points? If not, why not?

    34. Tips for Arguing Well Examine all arguments and explanations – your own and the ones you read. Can you see how the conclusions follow as inferences from the starting-points? If not, why not? Is the problem a gap in reasoning? A gap in the evidence the author gives? Something else? Examine the principles that you (and the authors you read) use to make inferences. Try to articulate them. For example, does the author seem to reach the conclusion that kangaroo migrations cause tsunamis because he or she has observed that tsunamis often follow kangaroo migrations? If so, he or she is reasoning fallaciously, in that…

    35. Tips for Arguing Well … ‘after’ does not by itself imply ‘because.’

    36. Tips for Arguing Well Show all work. Show how and why your data support your conclusion. Make sure you understand how (or whether) other authors’ data support their conclusions. The end of an argument neither justifies nor replaces the means. Take extra care to examine the reasoning of authors whose ideas or conclusions you agree with. The fact that you are sympathetic to someone’s position does not mean that this person has presented a valid argument, or accurate evidence, for what he or she is saying. It’s easy to take for granted that someone who agrees with you has good reasons to do so.

    37. Tips for Arguing Well Ask a friend – or better still, an enemy – to read what you’ve written, and ask if he or she thinks you’ve supported your conclusions adequately. Then return the favor.

    38. “By no means did the gods reveal all things to mortals from the beginning, but in time, by searching, mortals discover better.” - Xenophanes (6th century BCE)

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