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This will be the new version of my "Logic" thread in PF v2.0. I'll get my logic notes pasted into this forum ASAP, along with some of the more useful discussion from the old thread.
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Originally posted by ahrkron
I disagree. In a sense, the essence of logic is to find out what argumentative structures can definitely be "trusted" regardless of content, so that arguments can be analysed independently of how you "feel" about the conclusion they seem to produce.
Originally posted by quantumcarl
We have learned logic from the way the universe works. We are mimicing what we see in the sequence of events with which the universe unfolds.
We have called logical sequence "logical sequence" in an attempt to harness the incredible logic witnessed in the structure and efficency of the universe.
Thats what I think about logic.
In a sense, the essence of logic is to find out what argumentative structures can definitely be "trusted" regardless of content, so that arguments can be analysed independently of how you "feel" about the conclusion they seem to produce.
Originally posted by Tom
Hey folks, glad to see you all talking. My notes are coming up, slowly but surely, here:
https://www.physicsforums.com/showthread.php?s=&threadid=111
It is taking me a little while to translate all the color and smiley brackets to the new forum.
The more meaningful discussion in the PF v2.0 version of this thread centered on...
1. The Principle of Charity
This is an admonishment to make another person's argument as good as possible. This means, first and foremost, try to make the argument deductively valid whenever possible. If not possible, then try to make the argument a strong inductive argument. A strong inductive argument is preferable to a valid deductive argument with questionable premises.
Why do all this? Because the whole point of debate is to learn, not to be agreed with. If you make your opponent's argument as good as possible and, in the process, discover that he is correct, then you have learned something. If, on the other hand, you discover that his best argument is fallacious, then again, you have learned something.
2. The Difference Between Deductive and Inductive Arguments.
This was done via exercises that I posted. Audacity Dan posted his solutions, but unfortunately I did not copy them.
I'll put the exercises back up shortly, along with the rest of my notes.
All cattle are animals.Argument 1:
All paramecia are single-celled organisms.
No sea urchins are paramecia.
Therefore, no sea urchins are single-celled organisms.
Some people use logic.Argument 2:
Some Englishmen are Protestants.
Winston Churchill was a Protestant.
Therefore, Winston Churchill was an Englishman.
If a lifeform is a plant, then it reproduces.Argument 3:
If an animal is a mammal, then it bears its young live.
A gorilla bears its young live.
Therefore, a gorilla is a mammal.
Some oranges are rotten oranges.Argument 4:
Some dogs are good pets.
Some dogs are terriers.
Therefore, some terriers are good pets.
Originally posted by CJames
Argument 2:
Some Englishmen are Protestants.
Winston Churchill was a Protestant.
Therefore, Winston Churchill was an Englishman.
Some people use logic.
Lifegazer is a person.
Therefore, Lifegazer uses logic...I couldn't help it. I'm so rude. That was uncalled for.
Originally posted by Kerrie
i did not read through every single post of your last thread on logic tom, however, it would seem "right" to me that logic is subjective, at least when i am referring to the reasoning and rationalizing form of logic...
Originally posted by Tom
In PF v2.0, I posted some exercises to reinforce the material covered in the notes. Audacity Dan (now Dissident Dan) posted his solutions to the first set. If you would like to see them, then cough up the $20 for the archive CD.
Here are some exercises that cover Chapter 0 pretty comprehensively.
Disproof by Counterexample
Each of the following deductive arguments is invalid. Provide a counterexample for each.
Argument 1:
All paramecia are single-celled organisms.
No sea urchins are paramecia.
Therefore, no sea urchins are single-celled organisms.
Argument 2:
Some Englishmen are Protestants.
Winston Churchill was a Protestant.
Therefore, Winston Churchill was an Englishman.
Argument 3:
If an animal is a mammal, then it bears its young live.
A gorilla bears its young live.
Therefore, a gorilla is a mammal.
Argument 4:
Some dogs are good pets.
Some dogs are terriers.
Therefore, some terriers are good pets.
Deductive or Inductive?
Examine each argument below. Is the argument deductive or inductive? Explain.
Argument 1:
All human choices are determined, since all events in the universe are determined and all human choices are events in the universe.
Argument 2:
All birds can fly. I’ve never seen one that can’t.
Argument 3:
Today is Wednesday. You came 4 days ago, so that means you came on Saturday.
Argument 4:
I sent her the letter 3 weeks ago and have still received no answer; therefore, my letter must have been lost in the mail.
Argument 5:
A=B and B=C, therefore A=C.
Argument Analysis and Charity
Assuming ordinary context, examine each of the following arguments. Identify the conclusion and the premises, and supply a missing premise that would make the argument deductively valid.
Argument 1:
Bats are not birds, because birds have feathers.
Argument 2:
The baseball game was dull, since both teams played poorly.
Argument 3:
This liquid is not acid, for the litmus paper we placed in it did not turn red.
Argument 4:
He passed the examination; therefore, he must have lied.
Originally posted by Mentat
These are probably all wrong, but it was fun trying. [/B]
Originally posted by Tom
Thanks Mentat for "keeping me company".
No, they are all correct.
Originally posted by Mentat
Does the book ever touch on the fact that Inductive Logic shows Deductive Logic to be paradoxical, and that Deductive Logic does the same to Inductive Logic?
What is the name of the book that you were studying (it seems extremely informative).
Originally posted by Tom
No, and I've never heard of that. Can you explain?
It's called Logic, by David Baum. Just a first textbook on the subject.
So far, we slowly crawled through the introduction, and we are about half way through the first of two chapters on syllogistic logic. I'll post some more by the end of the week.
I really want to get to symbolic logic, because that's where the power of deductive reasoning gets a huge boost.
Originally posted by Mentat
And so it goes on. This is an Inductive approach, in that I am telling you that, no matter how many new propositions you produce, you will still never resolve this paradox.
3) Therefore, Inductive Logic is based on trying something an infinite amount of times, and is thus not "proof" of anything.
Originally posted by Tom
It seems that all this does is highlight incompleteness: that the formal system has axioms that cannot be proved within the system. That's not a paradox.
I don't want to get into Goedel here at all in this topic. Indeed, I have another dormant topic in the Math forum that is moving towards that (I think it's time to revive that one, too). This thread is about using logic, whereas discussions such as this are more along the lines of proving things about logic, which is not what I'm after here. Basically, I started this thread for people like Lifegazer and Alexander so I could stop repeating the same explanations of their fallacies, and instead cut and paste sections from the Logic Notes.
Now this is mentioned in the Introduction, and I covered it in the Logic Notes. It is openly admitted that induction is not proof, and the book stresses the fact that terms such as "sound" are reserved strictly for deductive arguments, and that such absolute terms would be misplaced on an argument that gives only partial support for its conclusion.
Originally posted by Mentat
True. However, it does show that Inductive Reasoning is required to show the flaw in Deductive Logic, and vice versa.
Side Note: Science is based on the Inductive Method, so shouldn't it be viewed as giving only "partial support", as you put it?