FallaciesS谬误

Logical Fallacies,Do you find these statements convincing?,1. All people in China like drinking tea.,3. I was watching TV and saw Yao Ming was introducing Pin-an Insurance. I am going to buy Ping-an Insurance because it must be the best (insurance).,2. Every Chinese speaks Putonghua.,3. Last year, I ate ice-cream before I took the final, and I failed in the exam. Last month, I ate ice-cream before the mid-term, and I failed again. I should not eat ice-cream before any examinations.,4. I went to the police station yesterday. I saw a policewoman in front of the door, another policewoman by the door, and another two policewomen was sitting behind the desk. All the officials of the station are female!,What does the man believe?,Logical Fallacies Mistakes in reasoning,Logical fallacies occur in our daily life. To make a strong argument, it is essential to learn identifying logical fallacies,We are going to learn eleven common logical fallacies.,Ad Hominem,Attacking or praising a person rather than the argument itself.,1. A: Which lecture do you like, Lis or Zhangs? B: Lis lectures are not good, he is old and short. But Zhangs lectures are good, because she is very pretty and charming.,For example:,2. You should not support the presidents policy. He is a heavy smoker. Besides, he is from a remote area.,Either or arguments (false dichotomy),Reduce complex issues to black and white.Present only two options as being possible when there may be other options.,e.g.1. If you dont get into 清华北大, it is not worth studying at any other universities.,2. Either you donate money to the project or you leave the community.,Slippery slope ( Ad Continuum),This fallacy suggests that one step will inevitably lead to more negative steps. It argues that the descent is inevitable and unalterable.,Father said to son, “ If you are not able to pass the final exam, you will not be accepted to a good high school, and you will not be able to go to a university, then you will not get a good job. Eventually, you will not be able to survive!”,Appeal to celebrity,This fallacy implies that something or somebody is good because a popular celebrity endorsed it (him/her).,e.g.Pepsi is the best drink because it is Zhou Jieluns choice!,Appeal to Popularity,This fallacy suggests that an idea must be true because a lot of people believe it. However, the idea quite often is mistaken.,e.g.1. A lot of people believe that the more tea you drink, the more health you will be.,2. Private vehicle control is bad, because many citizens oppose it.,This is the way we have always done it. Therefore, it is the right way!”,Appeal to tradition / Past /Antiquity,Believing that something is better because it is older and traditional.,e.g. Ginger姜 tea is good for fever发烧 because people have been drinking it for thousands of years.,Japanese fishermen defend the killing of whales and dolphins海豚 for food because it is “a cultural tradition that our ancestors祖先 used to do.”,Sweeping generalization,This fallacy is making assumptions about a whole group based on an inadequate and unqualified generalization. Applies a general statement too broadly, without considering possible exceptions.,1.All Americans have blue eyes and golden hair.,2. Terrorism happens everywhere in the world and it is a problem for all countries.,3. It is common knowledge that pollution has become a serious problem all over the world.,Hasty generalization,This fallacy draws a conclusion from too few examples,李明, 王红, 陈云, and 张强 are Level 5 students, they can speak French. All Level 5 students can speak French.,According to a study by the University of Hong Kong, fertilizer 肥料 is toxic 有毒 to humans. The solution is to stop using fertilizers.,Comment: The speaker jumps into a conclusion based on one study only!,Post hoc (false cause),This fallacy assumes a faulty causal relationship. One event following another in time does not mean that the first event caused the later one.,Last April, Mary went camping野营 with us, and it rained. Last month Mary went camping with my friends, and it rained. Lets not invite Mary to our out-door party, it will rain when she comes!,The percentage of engineers in Guangdong is 80% male and 20% female. If women are smart enough to work as engineers, there would be more female engineers.,Does x really caused y ?,Post Hoc: Relation does not equal cause,does not cause,The Rooster Crows,The sun rises,vaccine 疫苗 autism自闭症,Post hoc (false cause),Other Possible Causes?,Faulty analogies (1),Faulty analogies lead to faulty conclusions, relating situations that are not really similar or that are not similar in relevant ways.,1 is a number , 2 is a number. Therefore, 1 = 2.,Apples are fruit. Bananas are fruit. So, Apples are bananas.,The employees receive their salary. Now they are fighting for a higher income. It is like children demand more ice-creams after they have had one.,Trying to prepare a couple to be married without allowing them to live together first is like trying to teach kids how to swim without letting them get in the pool.,Comment: Statistics have shown that not living together before marriage leads to happier marriages.,Faulty analogies (2)For example:,Straw Man (1),A makes an argument (holds position/claim) x. B intends to defeat A and tries to do the following:,1. In order to misrepresent歪曲 As x, B claims y .,2. B attacks y in order to show:,3. As x is false / weak / incorrect.,Person A and Person B are having a debate.,For example:,Straw man (2),A: People should be careful with information from the Internet. x,B: 1. The Internet contains rubbish information. y 2. The Internet is of no value. 3. People should not get information from the Internet.,Bs first premise前提 misrepresents歪曲 As x (y). Bs second premise attacks his misrepresentation of x (y). Bs conclusion states that x is weak.,Straw Man (3),Misrepresenting歪曲 (exaggerating, over-simplifying, etc.) a position in order to m