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Logic Logical Fallacies

Oct 09, 2015



Adham Benhawy

Logical Fallacies- Presentation
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How to avoid bias and logical fallacies

How to avoid bias andlogical fallacies

Arguments persuade your audience that your ideas are valid or more valid than someone elses.

Strong arguments are logical and credible, but not all arguments are strong. Weak arguments rely on illogical statements called fallacies.

Logical FallaciesFallacies are statements that weaken arguments. Fallacy comes from the Latin word fallacia which means deceit, lead into error or trick. Fallacy is an error in reasoning. These flawed statements often sound true. Do not fall victim to such errors.Fallacies are defects that discredit argumentsA logical fallacy is an error in reasoning that makes the argument invalid.

1) False causes - Non sequitur (Latin for it does not follow) -the error is due to lack of logical connection

-to describe a statement in which premise and conclusion are totally unrelated but which is used as if they were

1) False causes - Non sequitur (Latin for it does not follow) - example

1) False causes - Non sequitur (Latin for it does not follow)-examples The President graduated from Harvard. He cant make mistakesBill lives in a large building, so his apartment must be large.Mona is a very petite lady, however she drives a huge car / truck.

1) False causes - Non sequitur (Latin for it does not follow)-examples "I hear the rain falling outside my window; therefore, the sun is not shining." (The conclusion is a non-sequitur because the sun can shine while it is raining.)Smoking cigarettes is dangerous, but nearly everything in life has some danger, such as driving a car or crossing a street. So, if you are willing to drive a car, you should be also willing to smoke.2) Oversimplification-multiple causes are reduced to just one or a few (oversimplification)2) Oversimplification - exampleThe overpopulation in Egypt is the main cause for poverty and unemployment.(this issue is more complex, there are many more factors for poverty, plus big countries like China, India, Brasil have flourishing economies;Communities and companies with many people, if well organized, produce and market better)

2) Oversimplification-exampleSchool violence has gone up and academic performance has gone down ever since organized prayer was banned form public schools. Therefore prayer should be reintroduced, resulting in school improvement. (This is an oversimplification because there are a handful of causes for school violence but the absence of organized prayer in schools.)2) Oversimplification - example

Mubarak dies and meets Nasser and Sadat in the afterlife. They ask him, "Poison or parade?" (Conspiracy theorists allege Nasser was poisoned; Sadat was assassinated during a military parade.) Mubarak shrugs and answers: "Facebook." 3) Camels nose- Slippery slope

-there is a saying about how if you allow a camel to poke his nose into the tent, soon the whole camel will follow. The fallacy here is the assumption that something is wrong because it could slide towards something that is wrong. -asserting that some event must be inevitably follow from another without any argument for the inevitability of the event in question. -the arguer claims that a sort of chain reaction, usually ending in some dire consequence, will take place, but there's really not enough evidence for that assumption. The arguer asserts that if we take even one step onto the "slippery slope," we will end up sliding all the way to the bottom; he or she assumes we can't stop halfway down the hill.

3) Camels nose- Slippery slopeOne cold night, as an Arab sat in his tent, a camel gently thrust his nose under the flap and looked in. Master, he said, let me put my nose in your tent. Its cold and stormy out here. By all means, said the Arab, and welcome as he turned over and went to sleep. A little later the Arab awoke to find that the camel had not only put his nose in the tent but his head and neck also. The camel, who had been turning his head from side to side, said, I will take but little more room if I place my forelegs within the tent. It is difficult standing out here. Yes, you may put your forelegs within, said the Arab, moving a little to make room, for the tent was small. Finally, the camel said, May I not stand wholly inside? I keep the tent open by standing as I do. Yes, yes, said the Arab. Come wholly inside. Perhaps it will be better for both of us. So the camel crowded in. The Arab with difficulty in the crowded quarters again went to sleep. When he woke up the next time, he was outside in the cold and the camel had the tent to himself

3) Camels nose- Slippery slope - exampleAnimal experimentation reduces our respect for life. If we don't respect life, we are likely to be more and more tolerant of violent acts like war and murder. Soon our society will become a battlefield in which everyone constantly fears for their lives. It will be the end of civilization. To prevent this terrible consequence, we should make animal experimentation illegal right now.

3) Camels nose- Slippery slope - examplesIf I fail English 101, I won't be able to graduate. If I don't graduate, I probably won't be able to get a good job, and I may very well end up doing temp work or flipping burgers for the next year.If the current situation continues, the stock exchange will plunge further causing the Egyptian Pound to fall against the other currencies, the country will be in free fall, the economic life will collapse (being first terribly hit due to disablement of the mobile telecommunications and the Internet connection), no tourists will be visiting for years to come and Egypt will become one of the poorest countries in Africa.

3) Camels nose- Slippery slopeNOT ALWAYS THE INTERMEDIATE STEPS ARE MENTIONED-ExamplesWe have to stop the tuition increase. The next thing you know, they will be charging 40 000 $ per semester!You can never give anyone a break. If you do, they will walk all over you.Allowing abortion in the first week of pregnancy would lead to allowing it in the ninth month.If we legalize marijuana, then more people will try heroin.If I make an exception for you than I will have to make an exception for everyoneIf we allow doctor assisted suicide, then eventually the government will control how we die.

4) Black cat fallacy -Post Hoc Ergo Propter Hoc (Latin for after this, therefore because of this) -attributes a cause-effect relation simply because something occurs after something -it happened after, so it was caused by it.-A occurred, then B occurred. Therefore A caused B.

4) Black cat fallacy -Post Hoc Ergo Propter Hoc (Latin for after this, therefore because of this) - examplesA black cat crossed my path before I took the math test; I ended up failing the test because of that cat!

The cock always crows just before sunrise. The rooster crows, and therefore the sun rises.The rooster crowed and the sun came out. Therefore the rooster made the sun came up

4) Black cat fallacy -Post Hoc Ergo Propter Hoc (Latin for after this, therefore because of this) -examplesOur weather pattern changed since we began launching the space shuttle in space"Before women got the vote, there were no nuclear weapons.

4) Black cat fallacy -Post Hoc Ergo Propter Hoc (Latin for after this, therefore because of this) -examplesAfter Billy was vaccinated, he developed autism, therefore vaccine caused his autism

She got sick after she visited China, so something in China caused her sickness. (Similar to a non sequitur, but time dependent.) Perhaps her sickness derived from something entirely independent from China.

5) Circular reasoning repeats a premise rather than giving a valid reason-the conclusion of the argument merely restates a possibly false premise in a slightly different language, nothing new!-circular reasoning occurs when the reasoner begins with what he or she is trying to end up with. -a conclusion is derived from premises that presuppose the conclusion. Normally, the point of good reasoning is to start out at one place and end up somewhere new, namely having reached the goal of increasing the degree of reasonable belief in the conclusion. The point is to make progress, but there is no progress.

5) Circular reasoning - example

5) Circular reasoning - examples Ford Motor Company clearly produces the finest cars in the US. We know they produce the finest cars because they have the best design engineers. This is true because they can afford to pay them more that other manufacturers. Obviously they can afford to pay them more because they produce the finest cars in the US

5) Circular reasoning - examples Martha is a good supervisor because she supervises the companys personnel office effectively.Only a fatalist would bungee jump and the fact that bungee jumpers are fatalist is a proof of this.

Change is good because when things dont remain the same, it is beneficial.

5) Circular reasoning - example Women shouldnt fight bulls because a bullfighter is and should be a man said the Bullfighters Association president. The president is saying basically that women shouldnt fight bulls because women shouldnt fight bulls. This reasoning isnt making any progress.

5) Circular reasoning-example Active euthanasia is morally acceptable. It is a decent, ethical thing to help another human being escape suffering through death. (the arguer has really just said the same thing twice: "decent, ethical" means pretty much the same thing as "morally acceptable," and "help another human being escape suffering through death" means "active euthanasia." So the premise basically says, "active euthanasia is morally acceptable," just like the conclusion does! The arguer hasn't yet given us any real reasons why euthanasia is acceptable; instead, she has left us asking "well, really, why do you think active euthanasia is acceptable?" Her argument "begs" (that is, evades) the real question.)

6) Black or white reasoning (Either or reasoning) False dilemma or false dichotonomy

-a claim that presents an artificially limited range of choices, but most situations provide more than 2 possible outcomes -a person who unfairly presents too few choices and then implies that a choice must be made among this short menu of choices commits the false dilemma fallacy, as does the person who accepts this faulty reasoning.-reducing a set of many possibilities to only two-the arguer then eliminates the undesirable alternative, leaving the desirable one as the conclusion.-you either like it or you don't. He either stands guilty or not guilty. Many times, a continuum occurs between the extremes that people fail to see. The universe also contains many "maybes."

6) Black or white reasoning (Either or reasoning) False dilemma or false dichotonomy - examples

George Bush: You are either for us or against us (either you are with Americas fight against terrorism or you are Americas enemy) If you don't support our president invading Iraq then you must love Muslim terrorists."Vote for me or the terrorists will attack." You are given a choice between two things you might not want, but one choice being infinitely undesirable as to induce you to choose the other.Are we going to increase the number of police officers in this city or are we going to abandon it to thugs, gangs and drug dealers?

6) Black or white reasoning (Either or reasoning) False dilemma or false dichotonomy - examplesassuming Atheism is the only alternative to Fundamentalism being a traitor is the only alternative to being a loud patriot"Caldwell Hall is in bad shape. Either we tear it down and put up a new building, or we continue to risk students' safety. Obviously we shouldn't risk anyone's safety, so we must tear the building down.There are only 2 solutions for the question of how the Universe was created: the Big Bang or Creation

6) Black or white reasoning (Either or reasoning) False dilemma or false dichotonomy - exampleSuddenly a horrific security vacuum took place when the ex-minister of interior ordered his people to withdraw from the scene and just for every personnel to seek his own protection. There will be no protection without the police that is linked to the government: you either support it or you will risk your life at the hands of thugs and gangs storming the city

7) Personal attack -Ad hominem (Latin for against the man)

-attacks the person rather than the issue, name calling -an arguer who uses ad hominem attacks the person instead of the argument.-whenever an arguer cannot defend his position with evidence, facts or reason, he/she may resort to attacking the opponent.

7) Personal attack -Ad hominem (Latin for against the man) - example

7) Personal attack -Ad hominem (Latin for against the man)You feel that abortion should be legal, but I disagree, because you are uneducated and poor.He is physically addicted to nicotine. Off course he defends smoking.Mr Smith is not an effective leader because he has ugly pointed ears.Sam is divorced, so how can he make sound financial decisions for the city?Dr Browns books on plant genetics are worthless because he is a convicted forger and embezzler.

7) Personal attack -Ad hominem (Latin for against the man)BUT IN SCIENCE NAME CALLING DOES NOT HAPPEN

If Einstein were caught practicing witchcraft, this would not invalidate his theory of relativity 8) The Red Herring argument-named after a strong smelling fish - ringa?

-beside the point -distract the audience from the issue through the introduction of some irrelevancy. -draws attention away from the main issue by focusing on a side issue or something irrelevant-a deliberate attempt to divert a process of enquiry by changing the subject-the introduction of a topic not related to the subject at hand-the arguer diverts the attention of the reader or listener by changing the subject to a different but sometimes subtly related onechanging the subject to something unrelated to the question. take the focus away from the topic at hand.

8) The Red Herring argumentThe basic idea is to "win" an argument by leading attention away from the argument and to another topic. This sort of "reasoning" has the following form: -Topic A is under discussion. -Topic B is introduced under the guise of being relevant to topic A (when topic B is actually not relevant to topic A). -Topic A is abandoned. This sort of "reasoning" is fallacious because merely changing the topic of discussion hardly counts as an argument against a claim.

8) Red Herring - examplesPolice officer: Do you know why I pulled you over? Motorist: No, but shouldnt you spending your time going after real criminals like murderers and thieves?

Some say that auto insurance rates needs to be more strictly regulated, but how strict are regulations on health insurance?

-It is my contention that the Flying Spaghetti Monster does exist-What evidence do you have to support such assertion?-Oh, there is plenty of evidence. It is all around us. BESIDES, LOOK AT HOW I AM STANDING ON ONE LEG !

8) Red Herring fallacy- example8) Red Herring - examples You are not fair in denying me the opportunity to make up the quiz; after all, I am paying for my own education and I work 2 jobs, I have to raise my 6 children on my own.

"I don't think Professor Jones should be given tenure. After all, the tenure system only leads to lazy professors who spend too much time on research and not enough on teaching." The topic was about whether Jones has met the criteria established for granting her tenure, not about the tenure system itself.

8) Red HerringThe former Egyptian government was corrupted and the former president was not the best leader, but look at whats happening in Libya?

9)Straw man argument ridicule and twist your opponents views

-to create a position that is easy to refute, then attribute that position to the opponent -attributes untrue characteristics to an argument and then attacks the argument based on those characteristics.-the arguer sets up a wimpy version of the opponents position and tries to score points by knocking it down. But just as being able to knock down a straw man, or a scarecrow, isn't very impressive, defeating a watered-down version of your opponents' argument isn't very impressive either.

9) Straw man-an arguer distorts an opponents argument for the purpose of more easily attacking it. -twisting someones position or argument so that it sounds ridiculous-a weak argument is attributed to the opposition, and then (easily) refuted -- in order to make it appear that you've refuted the opponent's entire position-purposely exaggerating or caricaturing or mocking an argument as a way to make it easier to attack -"A refutation of a caricature can be no more than a caricature of a refutation." -- Amos Tversky

-it is easy to knock down, and it is a poor substitute for a real man-imagine a fight in which one of the combatants sets up a man of straw, attacks it, then proclaims victory. All the while, the real opponent stands by untouched.9) Straw man - examples If relativity was right, my car would get shorter and heavier when I drive it. This is absurd, therefore relativity must be false.Evolution is false! How could a mouse evoluate into an elephant? Evolution is a ridiculous theory! Macro-evolution says that a fish can just evolve into a bird! Clearly this is preposterous!

9) Straw man - example You are opposed to building more B2 bombers. But if you had your way, we would have no national defense at all! Our nation couldn't exist long without a national defense!"The conclusion is then drawn: "We should build more B2 bombers." (Notice what happens here. The original position (no need for more B2 bombers) is distorted or exaggerated to become the claim that we don't need a national defense. This position (a "straw man") is then easily attacked.)

10) Traditional wisdomdont rock the boat-we should continue to do things as they have been done in the past, -we shouldnt challenge time-honored customs or traditions; -uses the logic that the way things use to be is better than they are now, ignoring all the problems of the past a practice must be OK today simply because it has been the apparently wise practice in the past, you commit the fallacy of traditional wisdom

10) Traditional wisdom - examplesMs Rickey says that all electronic devices should be banned from school because it was better without them in 1965.Off course we have to play Here comes the bride at our wedding because thats always been the song that is played.The Egyptian state has traditionally had a strength and solidity that made its collapse seem unthinkable."These rules were written 100 years ago and we have always followed them. Therefore, there is no need to change them."Women should stay at home, because women have always stayed at home."

10) Traditional wisdom - examplesOf course we should buy IBMs computer whenever we need new computers. We have been buying IBM as far back as anyone can remember.We should have a military government because we had it since 1952

11) Bandwagon omniscience- creates the impression that everybody is doing it and so should you

Everybody is trying Mc Donalds new McMudBurger, so should you.The majority of people like soda. Therefore, soda is good.More and more people are buying sports utility vehicles. Isnt it time you bought one, too? (you commit the fallacy if you buy the vehicle solely because of this advertisement) You should vote for Joe Blow because most people areOur product is the best because more people are buying it.

11) Bandwagon

12) Appeal to pity arguer tries to get people to accept a conclusion by making them fell sorry for someoneIm positive that my work will meet your requirements. I really need the job since my grandmother is sick."I deserve a good grade in this course. If I don't pass, I'll flunk out of school and it will break my poor mother's heart."I did not murder my mother and father with an axe! Please don't find me guilty; I'm suffering enough through being an orphan

13) Argument from authority

Einstein was very impressed with this theoryThe experts sayNewton believed in Creation. He was a great physicist. Surely you are not going to argue with him.