Aetherous

Study of Logic

15 posts in this topic

This thread will serve as an ongoing group study of Khan Academy's free Critical Thinking course, which is a study of Logic.

I will post one video each Friday, and plan on writing some notes from the video (might not happen due to having a busy life)...at that pace, the study of the course should end within a year.

After that time, I might move on to a Logic textbook for continuing the study here.

I've created this thread with the intention to keep it on track, so I applied for Owner Permissions to ensure that's the case. Please keep discussion confined to the lessons in the course. It's totally acceptable to discuss old lessons that we've moved on from.

If a conversation starts going off topic, please create a new thread for that conversation. I will edit it out of this thread, because the purpose here is the study of the course material.

I invite every Daobum to follow along, and at least watch the short weekly video which just takes a few minutes.

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  • Critical Thinking or being rational = making sure we have good reasons for our beliefs.

    • "Good" reasons = more probable, or certainly true.

  • "Bad" reasons = less probable, or absolutely untrue.

Argument = a set of statements called premises, which together comprise a reason for believing a conclusion. Arguments can be called good or bad.

  • Good argument = premises support the conclusion.

Bad argument = premises don't support the conclusion.

Deductive argument = where the truth of the premises guarantees the truth of the conclusion.

  • "If the premises are true, then the conclusion MUST be true".

But if the conclusion turns out to be false, then it was a bad argument (and therefore not a deductive argument), most likely due to the premises somehow being false.

Ampliative argument = Where the truth of the premises makes the conclusion probable, but not guaranteed.

  • Ampliative can be a "good argument", despite its conclusion sometimes being false. A conclusion being probable can still be a good reason for believing it.

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This is a good idea Aetherous, I have long advocated the study of logic in relation to esoteric subjects.  Here is a post that I did a while back on some games, many around since the Sixties when I first heard of them, that can make proficiency in thinking fun:
 

I don't think anyone has really noticed that the exemplar of the these "Ten Commandments" of logic, the Ten Commandments of the "Old Testament" are largely negative and state what one "Shalt not do", which is why these are a collection of logical fallacies, things which you shouldn't do in reasoning.  So all of this talk about these not being a guide to logic are misplaced, they are a guide to the rocky shoals which should be avoided.
 
As for waiting 'til a ripe old age to study dusty, boring books on logic, why not start now with your family and friends playing games such as "WFF 'n' Proof", a game of propositional calculus, or the game that deals with logical fallacies, "The Propaganda Game", you noobs can find out about what us Sixties math/science nerds have known for decades by going here:
 
Games for Thinkers
 
Then you can learn how to give a "Thinker's Damn".

 
Some discussion of these might be useful to this topic.
 
Also, a while back thelerner had the idea of using the Chat Room for investigation of the Socratic Method, a way of using logic to investigate belief structures, an investigation which I have called in several places on the Dao Bums, the most important form of self inquiry:
 

I was thinking about uses for chatroom. Something with a little more focus then the usual random conversations.

I read a book awhile back on the Socratic Method. Specifically people getting together to politely discuss specific ideas and concepts.

There were certain protocols to it. Maybe a leader whose job was to ask questions and keep the conversation lively.

Maybe we could experiment with that here. Pick a subject and time, do a count down and see how it goes. Subjects could.range fro. Simplicity to Karma.

Idea 2
Live lectures. Perhaps some could be led by teachers here. Set up a time, and discuss a system and allow for a Q and A afterwards. Doesn't have to be a teacher, anyone could set up a Lecture.

I find most of the time Chat is empty. Having a few specific events a week might be a good way to develop community.


This is an interesting suggestion, and for those who want to know more about "The Socratic Method", without buying a book, this site is virtually on online book on its history and uses:

The Socratic Method Research Portal

It is very well written, and useful resource for understanding what is really at the root of Western Philosophy.

Though people might still object to chat being taken up in a such a single issue way for long periods of time, so maybe this is another good reason to investigate the possibility of multiple chat rooms.

 

You might want to look at the site I mention for further ways this can develop.

 

Good luck to you, and all others who join you, in this most noble endeavor.

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II

 

Valid argument = "if the premises are true, then the conclusion must be true". An argument could have false premises (and therefore, a false conclusion) and still be considered to be "valid". Note that this is also the definition of a deductive argument.

Sound argument = a valid argument with true premises, and therefore a true conclusion. The prerequisite of being a sound argument is being valid.
Invalid argument = where both premises are true, but the conclusion is false.

Edited by Aetherous

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III

 

Abductive arguments = a kind of ampliative argument, where the premises don't guarantee the conclusion. It tries to provide the best explanation for something, rather than something we could rely on as absolute truth...and the explanation could be wrong despite being reasonable. The conclusion is supposed to be the best explanation for the premises.

Good explanations = they fit with what you already know, and they're not overly complicated.

How to make an abductive argument better = add more premises/more evidence, or come up with a better explanation. With half of the evidence, one could make a case for a certain explanation...but with more evidence, new things may come to light, and a different explanation may be required.

Edited by Aetherous
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Posted (edited)

IV

 

Necessary conditions

  • "Q is true only if P is true"...an example is that you can only be accepted to a university if you're a human. Being a human is necessary for that.

Sufficient conditions

  • "If P is true, then Q is true". The video uses the example of a 17 year old winning a science prize, and being accepted to the university because of that. It was sufficient to impress the university enough to accept them, but it wasn't necessary for all students to do the same in order to be accepted there.

Necessary but not Sufficient conditions

  • Example...steering well is one aspect of driving well, but if you only steer well you could still be a bad driver for other reasons.

Sufficient but not Necessary conditions

  • Example...boiling potatoes is sufficient for cooking them, but it's not necessary. There are other ways to cook a potato.

Both Necessary and Sufficient

  • Example...getting all of the answers right on the test is necessary for getting a perfect score. Why? Because it's necessary to get all answers right in order to get a perfect score. It's also sufficient if you get all answers right in order to get a perfect score.
Edited by Aetherous

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V

 

Necessary conditions

  • "P is necessary for Q, because P being true is needed for Q to be true".

Sufficient conditions

  • "R is sufficient for S, because R is all you need to get S; R is enough to get S".

Four potential combinations of necessary and sufficient:

  1. Necessary and Sufficient.
    1. Placing an order and paying for food is both necessary and sufficient for receiving that food.
  2. Necessary but not Sufficient (something that's needed for something else, but not enough for it)
    1. Moderate exercise on its own is necessary for health, but it's not sufficient because other things are needed as well...like a good diet.
  3. Sufficient but not Necessary
    1. Giving your dog a treat is sufficient to make him happy...but it's not necessary. He can be happy because of other reasons, such as throwing a ball.
  4. Neither Necessary nor Sufficient
    1. Mixing ingredients together is not sufficient to get a piece of cake, and it's also not necessary when you can just as easily go to the store and buy a piece of cake.

Background assumptions

  • We assume that things are working in a normal way...for instance, when ordering food at a restaurant, we assume that a meteor won't hit it. Or we assume that there aren't free french fries offered that day.
Edited by Aetherous

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VI



I'll be honest...my attention span was lost with those last two videos. I'll try to set aside some extra time to dig deep into them and get caught up here.

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Logic problems are fun:

 

http://www.puzzles.com/Projects/LogicProblemsArchive.html

 

You can write them out or do them in your head - either way they require a bit of stick-to-it-ness in the head to pull them off in one fell swoop. Most people can't stay tuned long enough for them.

 

I was a philosophy major 40 years ago - used to do these things for fun.

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VII

 



edit...life has been moving in fast forward, took the week off from posting these videos Edited by Aetherous

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