Loading presentation...

Present Remotely

Send the link below via email or IM


Present to your audience

Start remote presentation

  • Invited audience members will follow you as you navigate and present
  • People invited to a presentation do not need a Prezi account
  • This link expires 10 minutes after you close the presentation
  • A maximum of 30 users can follow your presentation
  • Learn more about this feature in our knowledge base article

Do you really want to delete this prezi?

Neither you, nor the coeditors you shared it with will be able to recover it again.


Make your likes visible on Facebook?

Connect your Facebook account to Prezi and let your likes appear on your timeline.
You can change this under Settings & Account at any time.

No, thanks

Monty Python and the Quest for the Perfect Fallacy

Disclaimer... some clips may be a bit insulting... it is for a reason!

Katherine Rica Hagen

on 1 May 2013

Comments (0)

Please log in to add your comment.

Report abuse

Transcript of Monty Python and the Quest for the Perfect Fallacy

This lesson will focus on 5 fallacies

and 5 booby traps
that represent
the most common

types of mistakes in thinking Dr. Roy Spencer, who is a prominent climate scientist at the University of Alabama and winner of NASA's medal for Expectional Scientific Achievement, doesnt think that humans are causing global warming. So, humans are probably not causing global warming... what is the problem? Types of Fallacies Genetic Fallacy For example... Red Herring An argument that pretends to establish a particular conclusion but that really argues for something else entirely. The origin of the term derives from fox-hunting, where a smoked herring (which the smoking process renders red) would be dragged across the trail of the fox to throw off the hounds. Straw Man A subcategory of red herring that involves misrepresenting an opponent’s position to make it easier to attack. The origin of the phrase derives from soldiers who learn to use bladed weapons by attacking straw-filled dummies – a much easier target than live people who are attempting to stab back. Examples? False Cause Labeling one thing as the cause of another thing on insufficient or unrepresentative evidence or using evidence that conflicts with established higher-level truths or theories. Undistributed Middle ? Dan White ate a lot of Twinkies and then killed the Mayor of San Francisco.
If I were a mayor, I’d ban Twinkies
so no one would kill me. Examples? Booby Traps A subcategory of vagueness that consists of using a term or expression in an argument in one sense in one place and in another sense in another. Monty Python and the Quest for the Perfect Fallacy A failure to mention or otherwise acknowledge important, relevant evidence. Suppressing evidence is not always a fallacy (for instance, defense lawyers are professionally obligated to ignore evidence of their client’s guilt), but ignoring relevant facts is often a sign of an attempt to mislead. Suppressed Evidence ANALYSIS: The problem, of course, is that selling a stock requires a purchaser for that stock. So if the holder of shares doesn’t sell them, it’s true that she has less money to reinvest, but it ignores the fact that the person who would have bought her shares now has whatever money he would have paid her to invest elsewhere. image unchecked... Example: Capital gains taxes keep people locked into their investments rather than moving to more productive investments. Someone who has to pay a large tax on her gains may be less inclined to sell stock, leaving her with less money to invest in new ventures. Appeal to Authority Accepting the word of authorities when we lack good reasons for thinking that they have the information we need or when we think that they might be biased, or when we ought to figure the matter out for ourselves, or when the authority in question is not really an expert in the relevant area. | - | - | - Questionable Use of Statistics - | - | - | Find the fallacy (or booby trap!) Fallacy: an argument that relies upon falty reasoning

Booby trap: an argument that, while not a fallacy, might lead

an inatentive reader to commit a fallacy Arguments can be bad for one of several reasons. They might fail because one of the premises was false or because they offer reasons that fail to support their conclusions OR because they are suppressing important evidence It appeals to authority, but the problem is that the argument leaves out an important
bit of information: overwhelming consensus in the scientific community is that global warming is being caused by humans... by suppressing important evidence,
the argument is potentially a booby-trap for unwary readers. Rejecting an argument based on its origins rather than on its own merits. A related form accepts or rejects arguments based on others who endorse or reject those same arguments. Examples? You think labor unions are good? You know who else liked labor unions? Karl Marx, that’s who.

ANALYSIS: The argument rejects labor unions on the grounds that Marx liked unions without making any reference to any of the present arguments for or against labor unions. Examples? You say that Coach Smith pressured teachers to give his students passing grades. But don’t you agree that athletics are important to schools? Don’t they build character?

ANALYSIS: The speaker shifts the subject from Coach Smith’s actions to the importance of athletics. Feminism is part of “a socialist, anti-family political movement that encourages women to leave their husbands, kill their children, practice witchcraft, destroy capitalism and become lesbians.” (Statement from Pat Robertson)
ANALYSIS: Well certainly we’d have good reason to oppose a political movement of that sort; fortunately, though, feminism does not hold any of those things. The argument assumes that eating Twinkies somehow causes mayors to be assassinated when no such causal connection has been demonstrated. (Note that White’s actual murder trial did invoke Twinkies as part of a diminished capacity argument, leading to what is now known as “the Twinkie defense.” Contrary to legend, however, the defense did not really argue that Twinkies caused White to commit murder. An argument in which the middle term is undistributed, meaning that not all the instances of things that are C are also instances of things that are A or of B. In other words, the first premise tells us that everything that is an A is also a C. It doesn’t tell us anything about whether things that are C are also things that are A. Similarly, in the second premise, we are told that everything that is a B is also a C. But again, we know nothing about things that are C.
A is a C.
B is a C.
Therefore A is a B.
The argument is seductive because of its surface similarity to a valid argument form:
A is a C.
C is a B.
Therefore A is a B.
In this argument, we know something about A (namely, that every instance of A is also an instance of C). And we also know something about C (namely, every instance of C is also an instance of B). Since the C is distributed in the second premise, we can correctly link A with B. EXAMPLE: Most Arabs are Muslims and all the 9/11 hijackers were also Muslims. Therefore most Arabs are hijackers. ANALYSIS: The conclusion doesn’t follow from the premises. To show this, substitute the following argument: My 5-year-old enjoys watching television, and teenagers also enjoy watching television. Therefore my 5-year-old is a teenager. Vagueness A lack of clarity or precision in language. Words or groups of words are vague when their meanings are inexact or when it is unclear to which things the word or words apply. Example? Your horoscope today: Small talk sometimes makes the world go 'round. A casual conversation at work or at a dinner party can spark something much greater than the sum of its parts. Go ahead and talk to multiple people about about many things ANALYSIS: What does it mean for a conversation to “spark something much greater than the sum of its parts”? It could mean just about anything, making the prediction true, but rather empty. Equivocation Any law can be repealed by the proper legal authority. The law of gravity is a law. Therefore, the law of gravity can be repealed by the proper legal authority.
ANALYSIS: The word “law” is being used in two different senses. EXAMPLE: Hi, I’m Troy McClure. You might remember me from such films as The Day the Peacock Died. After filming scenes with feathered co-stars all day, there’s nothing I enjoy more than a bucket of Buster’s Chicken. It’s chickentastic! ANALYSIS: While Troy might be an expert on making bad films, he has no particular expertise on fast food. Thus the fact that Troy McClure enjoys a particular sort of food is not a good reason for thinking that I ought to buy some. Employing statistics that are questionable without further support. There are several subcategories here. Hasty Conclusion: Accepting an argument on the basis of too little evidence. Small Sample: Drawing conclusions on the basis of a sample that is too small to be reliable. Unrepresentative Sample: Reasoning from a sample that is not representative of the general population. Women shouldn’t be concerned with wandering around in back alleys at night, since studies indicate that half of the rape committed takes place in the victim’s own home, while only one-twelfth happens in alleys. The argument uses statistics poorly; the argument is really about the likelihood of being raped in a back alley. Since women are in their homes far more frequently than they are in back alleys, it stands to reason that the sheer number of rapes will be higher in a victim’s home. But that tells us nothing at all about how likely it is that a woman wandering around a back alley will be raped. Example? What is the argument being offered? It is sometimes helpful to paraphrase it. You might consider writing down each premise as a separate line. Keep in mind that sometimes a larger argument might contain smaller sub-arguments. Remember a helpful tip for thinking about arguments: Look at a statement and then ask yourself, “Why should I believe that?” Then read the rest of the argument. If no other statement provides a reason for believing the one you just read, then the statement you’re looking at is probably a premise. If there is another statement that offers an answer to the why question, then the statement answering the why question is a premise, and the one you’re looking at is a conclusion.

Look at each conclusion. Now assess the reasons (premises) being offered for that conclusion. Ask yourselves two questions about those premises. (1) Do I have any cause to believe that the premises are true? (2) Do the premises logically support the conclusion?

Assess the arguments for fallacies and/or booby-traps. Do any of the arguments make logical errors? Might the arguments lead you to commit a fallacy? This is a special instance of the genetic fallacy, one common enough that some lists of fallacies include it as a separate instance. The basic structure of the argument is something like the following:

Person X did/said/believed some particular thing Y.
Hitler also did/said/believed Y.
Therefore, we ought to reject Y.

Therefore, person X is just as bad as Hitler.
The first of those conclusions is a genetic fallacy. The second possible conclusion is an undistributed middle. The “Bush-Hitler” ad is doing the second of those two things. This is a (humorous) instance of a false cause fallacy. In the commercial, drinking a Coke causes the old man to go out and do all the things that he’s never done before. Obviously, though, there is no evidence that drinking a Coke will actually cause this sort of behavior. This ad is fairly typical of a whole class of commercial advertisements. It is one long (very well done) red herring. The general approach is always the same: Invoke a number of positive images and then place your product at the very end. Many ads use sex in this way (e.g., Axe commercials, most beer commercials, Hardee’s/Carl’s Jr. ads, etc.) The Lexus spot provides quick cuts of multiple good images, with corresponding voice-over. At the end viewers are invited to savor all of life’s moments…while being treated to an image of a Lexus driving down the road. This ad from a 2006 House candidate commits too many fallacies to list individually. Easy examples: equivocating on “aliens,” suppressed evidence (that it is not, in fact, illegal to say “under God” in the pledge of allegiance; that Jackson and Sharpton support racial quotas which are, in fact, already illegal), and straw men (“you can burn the American flag and kill babies” pretty seriously oversimplifies the arguments at issue). Breakdown of the Argument
1. All witches are things that can burn.
2. All things that can burn are made of wood.
3. Therefore, all witches are made of wood. (from 1 & 2)
4. All things that are made of wood are things that can float.
5. All things that weigh as much as a duck are things that can float.
6. So all things that weigh as much as a duck are things that are made of wood. (from 4 & 5)
7. Therefore, all witches are things that weigh as much as a duck. (from 3 & 6)
8. This thing is a thing that weighs as much as a duck.
9. Therefore, this thing is a witch. (from 7 & 8) There are actually four arguments being made here. Lines (3), (6), (7) and (9) are all conclusions, with (9) being the main conclusion of the argument. Let’s take them one at a time.
The first argument:
1. All witches are things that can burn.
2. All things that can burn are made of wood.
3. Therefore, all witches are made of wood.
This is a valid argument. That is, (3) really does follow logically from (1) and (2). That’s not to say that it’s an especially convincing argument because premise (2) is rather obviously false. Still, if (2) were true, then the conclusion would have to be true as well. So this step is valid but unsound. The second argument:
4. All things that are made of wood are things that can float.
5. All things that weigh as much as a duck are things that can float.
6. So all things that weigh as much as a duck are things that are made of wood.
This argument commits the fallacy of the undistributed middle. The structure of the argument is the old familiar
All A is C.
All B is C.
Therefore, all A is B.
And that, of course, isn’t a valid argument. The third argument:
3. Therefore, all witches are made of wood.
6. So all things that weigh as much as a duck are things that are made of wood.
7. Therefore, all witches are things that weigh as much as a duck.
This argument has the same problem as the second argument. It’s also an undistributed middle. The fourth argument:
7. Therefore, all witches are things that weigh as much as a duck.
8. This thing is a thing that weighs as much as a duck.
9. Therefore, this thing is a witch.
Yes, once again, it’s an undistributed middle. Handout...
can you find the fallacy!?
Full transcript