A Note on Logic

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Quasi_Tenebrous

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The Umbravian University of St. Philip in the Shade has been commanded by His Opaque Highness Quasitenebrous VI to resolve for the good people of CAF a misconception regarding logic that is epidemic on these forums.

Logic is about correct reasoning, not correct answers. If someone says “all trees belong in antique shops,” it will not do any good to say “that’s not logical.” That is because the person may have arrived at his conclusion using means that are perfectly logical. For example:

“All trees are made of brass.”
“All things made of brass belong in antique shops.”
“Therefore, all trees belong in antique shops.”

The conclusion is logically valid; the fact that it is also inaccurate is because the premises are incorrect, not because he erred in reasoning.

So, the next time somebody says “all trees belong in antique shops,” your enlightened response should be “however did you come to think that?” You can then have a delightful exchange on just what brass is, or trees are, or if this sentence has any meaning anyway.

In a nutshell:
Logic = the method of reasoning
Accuracy = Is it right or wrong

This concludes the instruction in Logic 101 by the Umbravian University of St. Philip in the Shade. Go Shadowcats!
 
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All syllogisms have two premises and a conclusion.
Anything that has a conclusion is finished.
Therefore syllogisms are finished.
 
Quasi_Tenebrous said:
“All trees are made of brass.”
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Can a statement based on an illogical premise like “All trees are made of brass” actually be considered logical?

I say “nope”. Logic isn’t just the means by which you get to Point D from Point A.
 
Raxus said:
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Quasi_Tenebrous:
“All trees are made of brass.”
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Can a statement based on an illogical premise like “All trees are made of brass” actually be considered logical?

I say “nope”. Logic isn’t just the means by which you get to Point D from Point A.
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I think you are confusing knowledge and reasoning. Your knowledge, based on your experience, tells you that not all trees are made of brass. If you knew nothing at all about trees, no amount of reasoning would tell you what they are made of.
 
Alice: “That zebra is covered with stripes.”

Bob: “Yes, at least on this side.”
 
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Raxus said:
Can a statement based on an illogical premise like “All trees are made of brass” actually be considered logical?
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The court philosopher is instructed to reply:
A premise cannot be illogical, only incorrect. The word logic is misused by many people.

The reason logic has value is that its study preserves the truth of the arguments. It is possible to have correct premises, and an incorrect conclusion. Like this:

All bushes are plants.
All dandilions are plants.
Therefore, all bushes are dandilions.

That argument is illogical, because it involves a formal fallacy - which is only an error in reasoning.

The trees and brass example shows that you can also have false premises and a false conclusion, even if you’ve used logic properly. The only case that is impossible is to have true premises, and a valid argument, and yet have an incorrect conclusion. That is why logic is valuable; it preserves the truth of arguments.
 
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Maybe. It all starts to seem like semantics at this level, to me. I can understand why some would need to break it down that way, much like some folks break the English language down to minute levels; but for the vast majority of folks talking to each other about things, it doesn’t exactly serve a lot of purpose.
 
Beryllos said:
If you knew nothing at all about trees, no amount of reasoning would tell you what they are made of.
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I get what you’re saying, but I also feel like we’re almost focusing on the microscopic to point these kinds of things out. Anyone who’s ever seen a tree knows at the very least that they’re not made of metal, and it’s going to be a rare few who don’t. I don’t see much value in changing the entire way I phrase what I say for the sake of a very select few, in other words.

But there again, that’s more of a personal philosophy on my part than an logical argument. shrug Oh well.
 
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Raxus said:
Maybe. It all starts to seem like semantics at this level, to me.
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Well, that’s unfortunately the problem. If logic did not function this way, your computer would not work. “This is illogical” does not mean “I do not think this is right.” There is really no maybe about it.

The principles that determine if an argument is valid or fallacious are confirmed by many tools which logicians use such as truth tables, Ven diagrams, and Equivalence rules. Unlike many fields of study, though, the same logical rules are useful in specialized fields (e.g. computer science and analytics) and in everyday life (e.g. using logic to analyze an advertisement’s claims).

There are specialized parts of logic, which the ordinary person does not have much need for (Modal logic, or even predicate logic are examples), and it’s certainly not necessary for an amateur to know how to prove the validity of six-statement arguments using truth tables. That is not the same as knowing a few basic rules.
 
Raxus said:
Anyone who’s ever seen a tree knows at the very least that they’re not made of metal, and it’s going to be a rare few who don’t.
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You are too hung up on the example. Clearly, nobody believes that trees are made of metal. The example was chosen precisely because nobody believes trees are made of brass (nor that all brass things belong in antique shops). Its purpose was to demonstrate that logic is involved in reasoning, not in the truth-value of the propositions.

For that reason, the second example given by the Court Philosopher is drawn from true propositions. It is true that “all bushes are plants.” It is also true that “all dandelions are plants.” But you cannot, from that, extrapolate that “all bushes are dandelions.” Logic is the set of rules that demonstrates the difference between correct reasoning and incorrect thinking.
 
Ok. Words are wordy, and that level of extrapolation isn’t going to reach most, I think. Carry on.
 
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