When we talk about logic, we usually think of logic from the 19th century onwards.
However, this book is one that guides readers to easily acquire logical knowledge while restoring traditional logic represented by Aristotle and Kant.
Logic, which was established after the 19th century by mathematicians and some philosophers in response, has a narrow scope of inquiry.
Unlike traditional logic, which has a history of over 2,300 years, it is called mathematical logic, which reduces logic to the study of 'determining truth and falsity' among expressed sentences, excluding the subjective and psychological aspects in the human mind.


Humans think about anything and express those thoughts.
Everything in life is made up of thoughts and expressions, and the results of these thoughts and expressions influence happiness, wealth, and social status.
So, various skills were developed regarding how to think and how to express.
However, existing knowledge that has been known so far has not been well organized because it differs from person to person and its usefulness varies depending on the situation.
And although mathematical logic deals only with 'what has already been expressed' and guides us to which expressions are 'true' and which are erroneous, it is difficult to apply in real life because countless lies and errors naturally exist in the 'human mind'.
Are there no standards for human thought and expression? How do thoughts arise and how do errors arise? How do lies spread at breakneck speed and how does knowledge expand? Why do people persist in absurdity and even react emotionally? If we can find answers to these questions, we can gain valuable insights into humanity itself.
Through that insight, we can think better, choose more effective expressions, do better work, and achieve greater results.
You may also gain a better reputation by communicating better.
This book proposes such an answer under the name of logic.


Lessons 1 through 6 cover the basics of logic.
Here, it is stated that the logic dealt with in this book is not about sentences expressed outside the head, but about the “common human brain structure” inside the head.
A fascinating explanation is presented with various examples.
Lessons 7 through 13 are in-depth logic lessons.
Readers will gain a richer understanding of how humans acquire and expand knowledge, and how they become mired in error and cling to faulty knowledge.
In doing so, you gain a powerful weapon in terms of knowledge acquisition and communication.
How can we wisely apply our logical knowledge in real life? Lessons 14 through 17 answer this question with a variety of examples.
And there are four appendices.
Appendices are usually placed at the end of a book, but since readers tend not to read them, we intentionally changed the editing to place appendices in the middle of the book.
It corrects prejudices about logic and teaches the skills of reading logically and writing logically.
The final appendix examines the genealogy of philosophy using logic as its basic framework.
The reason why studying Western philosophy doesn't give us knowledge but instead just makes it all jumbled up in our heads is because we have a wrong understanding of logic.
To fully grasp the wisdom of Western philosophy, a restoration of logic is necessary, and this book faithfully fulfills that role.

There are various errors living and breathing in our heads, and we cannot logically eliminate them.
It is said that there are more bacteria living in our bodies than normal cells, but if we eliminate all the bacteria, humans will die.
The same goes for errors in the head.
A world of truth without any errors is not possible in the human mind.
Logic is a vessel that holds errors as well as truth, not a purifier that eliminates errors.

--- p.52

Studying logic will help you predict how far you can push your argument and what extent others will accept and be convinced.

--- p.71

There are three characteristics of the concept, so let's remember them well.
First, every concept has a size.
Let's use words of appropriate size.
Second, each concept has a different clarity in people's minds.
Let's use words with clearer meanings if possible.
Third, every concept has its own belonging.

--- p.109

In other words, if we want to know how we acquire knowledge and how we communicate (or should communicate), we have to go inside the human mind.
And the discipline that appears at that time is general logic, and the logic at that time is the logic that this book deals with.
Traditionally, logic deals only with forms, and this is no different whether it is general logic or mathematical logic.

--- p.118

The foundational structure model is a three-dimensional model, not a two-dimensional Venn diagram.
First there is the foundation, and then judgment is placed on it.
Universal concepts or principles form the foundation, and specific judgments arising from individual situations are placed on this foundation.
The universal that forms the foundation exerts its dominance over the individual.

--- p.169

There are countless major assumptions in the human mind and they are different for each person.
But if we assume that there is an immutable major premise that all humans have, then logic and metaphysics meet.

--- p.191

For a productive debate to occur, one must recognize the underlying assumptions that govern the argument.

--- p.219

The subject of the text is not 'me' but 'the persona I have chosen or must choose'.
Persona means mask, and is a word derived from the masks worn by characters in ancient Greek plays.
Psychologist Jung also claimed that humans have a thousand personas and that they use the appropriate persona depending on the situation and form social relationships.
'Mask Persona' is the 'Person' of writing.
As I said before, we write because we are in a situation where we have to write.
In that case, you choose a persona that fits the situation and write from that persona's perspective.

--- p.259

Conceptualization does not mean taking someone else's definition of meaning and bringing it into my head.
It's just simple memorization.
First, you have to discover the word through experience.
As in the previous example, if you are not attentive, the word will not be found.
Then you have to bring that word into your head.
And then make the meaning clear and remember it.
Training is needed.

--- p.297

In short, dialectics is a battle over priorities between major premises.
Apologetics is very important because the conclusion depends on what wins in this battle of priorities.

--- p.365

A fool who wastes time on useless thoughts should reduce the number of thoughts he has, and a person who lives his life with too narrow a focus or is at a loss to solve the problems he faces should expand the number of thoughts he has.
Just by reducing or increasing the size of your thought set, your life will change.

--- p.434

Therefore, we communicate with others through logic.
If you can express yourself logically, you are a good communicator. If you can't express yourself logically, you are a bad communicator.
People who are good at communicating gain empathy from others and are recognized for their abilities.

--- p.462

We must not forget that comparative logic can stimulate the other party's bias to our disadvantage and lead to the counterargument, "Isn't the situation different in this respect?"
If you use comparative logic incorrectly, the other person's argument will change from the validity of your argument to the validity of comparative logic.

--- p.478