Category Archives: Logic


After I read Stephen’s Guide to Logical Fallacies, I think logic is a very useful tool. In simple terms, I understood that “the flow of thought until a conclusion is reached”.

In Stephen’s Guide to Logical Fallacies, there is some example,

  1. Fred, the Australian, stole my wallet. Thus, all Australians are thieves. (Of course, we shouldn’t judge all Australians on the basis of one example.)

I think this is very exaggerated and not logical. The good logical analogy is “This store is always lined up” → “It must be popular” But both can be said to be logical because there is a way to get results.

“This store is always lined up” → “It must be popular”

“Australian store my wallet” → “All Australian are thieves”


Logic generally refers to the laws and rules of thinking and is also important in our daily lives. In class, we know two arguments, deductive and inductive.

All odd numbers are integers.
All even numbers are integers.
Therefore, all odd numbers are even numbers.

This is an example in the text, I think it is too hasty to use inductive.

Slothful Induction

The part that struck me as the most interesting thing that we read in class was the section about slothful induction. it is about denying something that obviously happened.

Hugo has had twelve accidents in the last six months, yet he insists that it is just a
coincidence and not his fault. (Inductively, the evidence is overwhelming that it is his
fault. This example borrowed from Barker, p. 189) [pg. 3]

I particularly liked this example because it made me laugh and made me think of how often I have come across this form of induction. I think that this is the easiest form of induction because to use it you just have to deny that whatever happened is not your fault.

The mind is not designed for thinking

In the real life, most of people think that the ability to reason is the most obvious thing to set human apart from other species. However, a seemingly correct view has certain flaws. Years after Shakespeare or other famous people made their points that Thinking is the hardest work,a growing number of scientists assert that human dont think frequently because our rbrains are designed for avoidance of thought. That is true.

Your brain serves many purposes, and thinking is not the one it serves best. Your brain also supports the ability to see and to move, for example, and these functions operate much more efficiently and reliably than your ability to think. It’s no accident that most of your brain’s real estate is devoted to these activities. The extra brain power is needed because seeing is actually more difficult than playing chess or solving calculus problems.

The examples that follow in the text prove this point that the ability to see and move is more essential perfectly. Like machines almost can do everything about thinking,especially for some repetitive calculation that our human need to think. But they cannot see,and dont know how to configure themselves or to think about novel ways to move or something like that,but our human just are able to accomplish this kind of thing,so these things are most valuable for us.


The text shows us how some logical fallacies and generalizations work. For example, if in Spain bullfighting is a tradition, then everyone must like it. Another topic we covered is how humans dislike thinking,  we like to take the easy way. That’s why teenagers dislike school, we go there to reconfigure our brain to think when it is against our nature.


I read all the handouts and I found that the contents of Stephen’s Guide to Logic’s Paradox have the greatest impact on me. In this handout, the author shows me how people abuse logic in several ways through practical examples. I think he is very right because these things can be said to be very common in my real life. People simply point out that something is logical, or that it contains some logic to think that something is real. For example, in China, my older generation thought that the length of an indoor umbrella would not be high. When I ask them why, they always tell you that this is what their parents told them. This is a very stubborn generalization, which means that the sample size is not large enough to support the conclusion. So something that people believe does not mean that it is correct.

TOK logic

In the last class discussion, we were talking about what people don’t like to think about. I agree with that, and I would say its human nature to make things easier for us, and less complicated. As an example, some people would say “teenagers don’t like going to school, because they have to train their brain and think, and people don’t like thinking”. Personally, I think it’s not true, and it also depends on a person and his abilities. TOK is that type og class, where people have to disagree or agree with statements or make their own.


I want to talk about a interesting concept in logiacal fallacies, here is the defination of it:”The person presenting an argument is attacked instead of the argument itself.” This happened a lot in our life, when people are arguing to eachothers one of them tend to attack their opponents directly,which is unfair since one of them already deny the person himself so whatever he said will become pointless.

Logic – Deductive Reasoning

I like deductive reasoning because it is simple and can be used in a variety of ways. I also like it because you can deduce that something is true because something similar is also true. This example stood out to me the most.

 if you know the general principle that the sum of the angles in any triangle is always 180 degrees, and you have a particular triangle in mind, you can then conclude that the sum of the angles in your triangle is 180 degrees.[3]

This quotation stood out to me the most because it made the most sense to me. Another example could be that is a particular square has four sides, then a square that is in your mind must also have four sides. This made the most sense to me.

Thinking logically

Thinking logically is to organizing causal relationships and considering them in order, or explaining them clearly.

For example, “I feel stomachache in summer”. “summer” and “feel a stomachache” does not have a relation.  It has be like this,

I eat ice-cream a lot in summer.→ Eating ice-cream makes stomachache.→So in summer when I often eat ice-cream, my stomach hurts.

It made easier to understand by  understanding the causal relationships between “summer” and “feel a stomachache”.

Logic posts

In the three articles we have read in the class from the past two classes, I like “Stephen’s Guide to the Logical Fallacies” the most. It introduces various inductive fallacies with clear definition and explanation, and give several examples for each fallacies, makes me understand each fallacy easily. After I read through the text, I found that those fallacies are always be used while people are trying to argue with somebody or to proof something.  Especially “Anonymous Authorities”(p.6), rumors are usually created based on this logic fallacy for example, “A government official said today that the new gun law will be proposed tomorrow. “. It is sound so persuasive because it is said by “Authorities”, but the point is the “Authorities” is anonymous, people can not confirm that the authority is an expert.


In document Stephen’s Guide to the Logical Fallacies, he introduced Inductive Fallacies and Changing the Subject. In part one Inductive Fallacies. He defined it means inferring from the properties of a sample to the properties of a population as a whole. It contains “Hasty Generalization”, the size of the sample is too small to support the conclusion; “Unrepresentative Sample”, the sample used in an inductive inference is relevantly different from the population as a whole; “False Analogy”, two objects A and B are similar, then if A has property P, B must have property P; “Slothful Induction”, the proper conclusion of an inductive argument is denied despite the evidence to the contrary; and “Fallacy of Exclusion”, important evidence which would undermine an inductive argument is excluded from consideration.

The Inductive fallacies happens all around us. We may defined the whole group by just meet a few of them; defined the quality of one dozen of apple by just try one of them.

Logic Fallacies (By Kirill)

Logic Fallacy: Unrepresentative Sample.

Often hear: “He was bad at school but now owns biggest company somewhere”. This is a great example, cause we better to look not onto the individuals, but statistics and trends. Such statement does not include that other 99%, who studied bad, now have no work, no salary. Nothing. It works because people want to believe in bright and wonderful future, ignoring reality and pretending to be somewhat spacial in comparison to others.

Logical Fallacies

Logic Fallacy: False analogy.

In my opinion, false analogy is one of the most common, tricky and hypocritical argument . From personal experience would say that it is common for parents to say: “If your friends would be jumping out from windows, you would do so to?”. But when some one needs you to do or not do something they give you false analogy of smokers/drug addicted/alcohol addicted not reaching the same social status as some actors or etc.

Logical thinking

I like it best and think the best article is Stephen’s Guide. This article provides several examples for us to refer to, and it is also good to know what is abusive reasoning. Some of the reasoning is not true, some of the reasoning is true, and the final answer is determined by the current situation.

There are two kinds of reasoning that are most common, inductive reasoning and deductive reasoning. These are the simplest and most commonly used, especially inductive reasoning, but with varying degrees of accuracy.

No inductive inference is perfect. That means that any inductive inference can sometimes fail. Even though the premises are true, the conclusion might be false. Nonetheless, a good inductive inference gives us a reason to believe that the conclusion is probably true.

A thought on Logical Fallacies

From the past two lessons in TOK, the most intriguing article to me was Stephen’s Guide to the Logical Fallacies. This article, not only defines the fallacies individually but also, gave examples for each to let the readers comprehend it better. Not only the format is really well made, but the content was even more interesting for our daily learning. Take science experiments, how do we make sure that the results we’ve got are fair and square? Were they achieved only under certain conditions (unrepresentative sample) or are they even scientifically valid (hasty generalization). Or take Geography, how will we know if a questionnaire’s results are trustworthy? Say, is it okay to say that the policies working in a More Economically Developed Country are definitely suitable for the Less Economic Developed Countries?

Thus, the importance of using correct logical reasoning matters crucially towards the difference between a persuasive, reasonable argument and some kid yapping about.


Logic is reasoning. It explains by reasoning from general to specific as we learn in class:


On the other hand,


is just from general to specific without any reasoning or explanation.

Meaning of Logic

I think logic refers not only to the law of thinking, but also to the subject of studying the law of thinking. On the other hand logic refers to law generally speaking, including the law of thinking and the law of objectivity. However there are many different kinds of explanation of logic. You could find another definition for logic in many things for example doing homework can let you know some logic work for paper writing or typing letter on the laptop.


Logic. It’s something not everybody seems to have. Especially in the common sense form. We use logic as a tool to justify something or to give something reason. For example, in math you may use previous knowledge as a form of logic to prove why your answer is correct. We use logic in our everyday lives all the time without even noticing. It’s as if it has been programmed into our brains that doing something logically or with reason is always better than without. Which of course seems obvious for us because we’ve been taught that our whole lives. The problem with logic, however, is that we use it for most if not everything, so we tend to stereotype when using it. For example, in the handout we saw the example of a hasty generalization. In the example, Australians were stereotyped to be thieves. Of course we know that that stereotype is not correct, therefore it is a wrong assumption. In more recent years we have become more aware of our stereotypes and how we are generalizing people, so assuming people’s spirituality, gender, sexuality, etc. has become more of a rocky topic to talk about due to the possibility of offending others. The reality is, we use logic for every decision and thought we make about pretty much everything and sometimes that results in wrong assumptions being made about a person or a place and that’s when logic becomes harmful.

Logical Fallacies: Changing the Subject Kelvin M.

Though referred to in Stephen’s Guide to Logical Fallacies as a logical fallacy, the technique of changing subject is very effective in debate. Or at least, I, personally, find it very effective when used correctly in my past debate experiences within class and is quite fond of practicing it unto my opponents.

Changing the subject subtly during debate can become a trap for the opponent to step into. Once the opponent chases you into it, it would be easy to disrupt his train of thought or even turn around to call your opponent guilty of changing the subject and drifting afar the debate question. This often works in a debate as both sides are actively engaged it thinking about their points, so that sometimes they ignore a subtle dirty move that is changing the subject, quote out of context, or simple misinterpretation.The most important aspect of applying this technique to real use is to do it subtly. If the intention is discovered by the opponent, it would become a flaw in your argument and let the opponent gain the upper hand.

Though when unknowingly used, changing the subject is a typical logical fallacy, it cannot be denied that it is a effective technique in debate when successfully executed.


One topic that we covered while learning about logic was reasoning. I found this topic in treating because before we started talking about this in class I did not know that there were more than 1 type of reasoning. The two types of reasoning that we talked about in our lessons about Logic were inductive and deductive reasoning.

Inductive reasoning is when you form a conclusion based on observations. When using inductive reasoning you form the conclusion that something must be true because something else that you observed was true. The problem with Inductive reasoning is that there is no proof to support the conclusions that you have formed. Although Inductive reasoning is not logically valid it is an important part of making discoveries in math.  Inductive reasoning can not show certainty but it is part of a discovery process where people are making observations and forming conclusions based on those observations that help to make new discoveries even if they are not proved.

Deductive reasoning is like the opposite of inductive reasoning. When using Deductive reasoning conclusions are formed when you know for certain that something is true it means that something else has to be true. Deductive reasoning is used if you are trying to prove with certainty that something. deductive reasoning is often used in mathematics. This can be helpful when you are needing to show that if one thing is true it would be impossible for something else to not be true as well.

Both Inductive and Deductive reasoning can be useful in different ways. They both relate to our lesson on logic because we learned that deductive reasoning is logical and Inductive is not.


unrepresentative sample

The definition of unrepresentative sample is that the sample used is very different from the population as a whole. For example: a lot of Canadians like hockey. That must mean that all Canadians like hockey. I chose this one because it shows that a lot of the time, people put groups of people, cultures, or things in one big box, like if one part of Canada normally votes mostly Liberal, then everyone in that part of Canada votes Liberal. That is probably not true, because everyone supports different political parties. The issue with unrepresentative sample is that it makes you think that everyone in Canada likes hockey, or everyone in the US is arrogant and does not care about the environment. This is a fallacy because it does not show that everyone has different personalities, and likes and dislikes, and instead it paints them all in the same colour.

TOK Plato’s ‘Meno’ Part 5 – Anh Tai Trang

Part 5 summarizes the entire Plato’s ‘Meno’ reading. The main point of this reading is that Socrates found a way to convince others by asking them different questions but in the end came back to the main topic and the people who were asked were completely convinced.


” Then the result of our reasoning, Meno, is found to be that virtue comes to us by a divine dispensation, when it does come. But the certainty of this we shall only know when, before asking in what way virtue comes to mankind, we set about inquiring what virtue is, in and by itself. It is time now for me to go my way, but do you persuade our friend Anytus of that whereof you are now yourself persuaded, so as to put him in a gentler mood; for if you can persuade him, you will do a good turn to the people of Athens also “. [page 47].