http://www.physicsforums.com/topic.asp?ARCHIVE=&TOPIC_ID=9125

http://www.physicsforums.com/topic.asp?ARCHIVE=&TOPIC_ID=9125

That you work and find the time and energy to put as much as you do into this forum defies logic!

Thanks for the effort.

I'll be following quietly, myself, til I make myself heard.

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Originally posted by Tom:
Anyone have any thoughts on this?

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Logic is what justifies the link between ideas. What I observe here (and in life as well), are people who join true ideas improperly. In such a case, each individual idea is true, and because they don’t understand the rules of logic, debates seem to go on endlessly as they defend the individual ideas; meanwhile, opponents are actually questioning the logical connections they’ve made between the ideas (and consequently the conclusions).

It would wonderful for everyone who participates here were to weigh in on this, and help forge a consensus about the rules of debate. With general consensus, at least we could refer back to what was agreed upon.

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Originally posted by LURCH_001:
Not sure I agree with the choice of "prescriptive" over "descriptive".

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The thing is, the word "law" is in fact used in those two ways. There are, for example, the "laws of physics" and there is the "law of the land". They are not the same, as the former cannot be broken or repealed, while the former can.

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For example; we would not say that imagining two headed goats "should not be" logic, but rather, that it "is not" logic. However, perhaps this difference will not be important to our discussion.

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Imagining two headed goats wouldn't be subject to the dichotomy of 'descriptive vs. prescriptive' reasoning, because it was ruled out with the first dichotomy of 'reasoning vs. nonreasoning'.

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Originally posted by schwartzchildradius999:
Can logic be applied in the strictest sense, or is our concept of it a reflection of an abstract natural order?

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I honestly don't know. I have seen Ahrkron say that our logic is a consequence of our observations or something like that. As far as this thread goes, I just want to explore the correct use of logic, and save questions of the nature of logic for another time. I want to get through Goedel's theorem before I do that.

I'll wrap up the introduction tomorrow, then we'll get into syllogisms.

I suggest that you make two topics for this subject, one topic in which you will put the text (the long replies) and another topic for the members to comment and talk about the subject.

This way the first topic can become a permanent reference of Logic in the forums (it can be locked and sent to top by Kerrie).

I think in this way the subject will be better, cause reading the comments with the original text is a little confusing in such an important subject.

Thanks a lot Tom for your efforts.

Glad you like the topic. I'm trying to wait a few days between posts so that anyone who cares to can discuss them. However, if you feel that this thread is getting too cumbersome, feel free to start an offshoot thread to discuss any of the points in detail.

Thanks again,

Tom

I saw something in this section that I feel should be of particular interest to the scientifically minded. It was the example given of how an argument containing flawed logic can reach a correct conclusion (courageous, considerate men). Of great importance is the fact that, if we did not already know that this conclusion is correct, we still would not. A correct conclusion that is supported by an invalid arguement is still not known to be correct.

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Originally posted by LURCH_001:
I saw something in this section that I feel should be of particular interest to scientifically minded. It was the example given of how an argument containing flawed logic can reach a correct conclusion (courageous, considerate men). Of great importance is the fact that, if we did not already know that this conclusion is correct, we still would not. A correct conclusion that is supported by an invalid arguement is still not known to be correct.

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I believe you are generally correct, but I do know of a class of illogical reasoning that might serve as a counterexample. If my mother says I love you because you are the most wonderful son in the world, I can't possibly agree (knowing myself) with her logic but I know she knows she loves me. There are things people say which they know (i.e., not just believe) because they've had sufficient experience with something for it to have achieved the status of "known." Although they don't understand how to logically justify it, when I hear someone speak from such experience I tend to overlook the fact that they can't explain it properly.

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Originally posted by LURCH_001:
I saw something in this section that I feel should be of particular interest to scientifically minded. It was the example given of how an argument containing flawed logic can reach a correct conclusion (courageous, considerate men).

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The thing is, the argument didn't really reach the conclusion. It was really just asserted as a third premise, but the author inserted the word "therefore" and used it as a "blank check" of sorts to present the argument as valid. Unfortunately, way too many people here do that. When we fully develop the formal mechanical decision procedure, we will be able to analyze many kinds of arguments. Counterexamples are kind of clumsy.

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Of great importance is the fact that, if we did not already know that this conclusion is correct, we still would not. A correct conclusion that is supported by an invalid arguement is still not known to be correct.

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Yes, and that is why I am an empiricist.

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Originally posted by LURCH_001:
I saw something in this section that I feel should be of particular interest to scientifically minded. It was the example given of how an argument containing flawed logic can reach a correct conclusion (courageous, considerate men). Of great importance is the fact that, if we did not already know that this conclusion is correct, we still would not. A correct conclusion that is supported by an invalid arguement is still not known to be correct.

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Yes, and I can say "There are speeding ducks, so the oceans are blue." The conclusion just happens to be correct (we know this from experience), but the premises do not support the conclusion. It's really another argument not mentioned there that tells us that the oceans are blue. It would go something like this:

There are oceans.
There is light.
There are people.
People have subjective experiences.
Colors are subjective experiences that are determined by electromagnetic wavelength.
The names for colors are determined by society.
Most light eminating/reflecting from the oceans during the daytime is of a narrow range of wavelengths.
Society calls this set of wavelengths "blue".
Therefore, the oceans are (mostly) blue (during the daytime).

So, we have a completely different, sound, valid argument that validates calling the oceans blue. Using this argument, we know that the oceans are blue, but the original ducks thing is not how we know this. The ducks argument happens to have a conclusion supported by other premises, but not its own.

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Originally posted by Tom:
[b]It should be noted, however, that very often the premises of deductive arguments are conclusions of inductive arguments (especially in science). We will get into the scientific method in Part III: Induction.

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I look forward to that. Great topic.