Logic should not be trusted.

[Seraiah]

[Why is it that when I click ‘save’ it destroys my post? Grrrrr.]

Quick version:
@gotlucky
Our disagreement sounds like symantics.

While logic isn’t a “purpose” in itself, it does have a purpose, and that purpose is to produce accurate conclusions if the premises are accurate and complete.

Since we can not know if the premises are accurate and complete, we can not trust logic to produce an accurate conclusion.

This is precisely why we perform experiments.

[gotlucky]

@Seraiah

While logic isn’t a “purpose” in itself, it does have a purpose, and that purpose is to produce accurate conclusions if the premises are accurate and complete.

The definition of logic, first from wikipedia:

Logic (from the Greek λογική logikē) is the study of valid reasoning. Logic is used in most intellectual activities, but is studied primarily in the disciplines of philosophy, mathematics, semantics, and computer science. It examines general forms that arguments may take, which forms are valid, and which are fallacies. In philosophy, the study of logic is applied in most major areas: metaphysics, law, ontology,epistemology, and ethics. In mathematics, it is the study of valid inferences within some formal language. Logic is also studied inargumentation theory.

Logic was studied in several ancient civilizations, including India, China, and Greece. In the West, logic was established as a formal discipline by Aristotle, who gave it a fundamental place in philosophy. The study of logic was part of the classical trivium, which also included grammar and rhetoric.

Logic is often divided into three parts, inductive reasoning, abductive reasoning, and deductive reasoning.

The definition of logic, from wiktionary:

Noun

Wikipedia has an article on:
Logic

logic (countable and uncountable; plural logics)

1. (uncountable) A method of human thought that involves thinking in a linear, step-by-step manner about how a problem can be solved. Logic is the basis of many principles including the scientific method.
2. (philosophy, logic) The study of the principles and criteria of valid inference and demonstration. [quotations ▼]
3. (uncountable) (mathematics) The mathematical study of relationships between rigorously defined concepts and of proof of statements.
4. (countable) (mathematics) A formal or informal language together with a deductive system or a model-theoretic semantics.
5. (uncountable) Any system of thought, whether rigorous and productive or not, especially one associated with a particular person.

   It’s hard to work out his system of logic.

6. (uncountable) The part of an electronic system that performs the boolean logic operations, short for logic gates or logic circuit.

   Fred is designing the logic for the new controller.

What you will notice is that logic is not a purpose, it is a tool. Logic is either the study of reasoning or it is method, a tool.

@Seraiah

Since we can not know if the premises are accurate and complete, we can not trust logic to produce an accurate conclusion.

I hope you get around to reading that essay I linked for you, as it really is very interesting. Two great sections from Asimov’s essay:

My answer to him was, “John, when people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together.”

The basic trouble, you see, is that people think that “right” and “wrong” are absolute; that everything that isn’t perfectly and completely right is totally and equally wrong.

However, I don’t think that’s so. It seems to me that right and wrong are fuzzy concepts, and I will devote this essay to an explanation of why I think so.

Naturally, the theories we now have might be considered wrong in the simplistic sense of my English Lit correspondent, but in a much truer and subtler sense, they need only be considered incomplete.

[Serpentis-Lucis]

@ Luminar

You still haven’t adequately addressed the issues I pointed out in my last post. Attempting to undermind logic is a very big task, requiring extensive thought on epistemology, which I am fairly certain you haven’t studied enough. The argument you presented in your last post still didn’t explain why Occam’s Razor is essential to logic, or rather it wasn’t a valid explanation.

[JackCuyler]

@Seraiah

A is B
C is B
Therefore
A is C

This is only true because it has always been true in testable, repeatable, observations.

Actually, you have that exactly backwards. It’s been true in testable, repeatable, observations because it’s true.

[gotlucky]

You both are wrong. That is an invalid argument:

Men are humans.

Women are humans.

Therefore, men are women.

It is an invalid argument.

[Laughing_Man]

“U trollin bro? I’m obviously not referring to the concepts or definitions.”

No I am being flippant.

[Aristophan3s]

@Torsten

I’m going to quote myself again:

@gotlucky

A false inference is a false conclusion, which can only result from a set of premises that has at least one false premise or is an incomplete set of premises, or the argument is invalid.

Now let’s look at what you said:

@Torsten

No, one can make false conclusions, while all stated premises are correct. People are just more difficult to convince that something is wrong, when they check the premises and find them to be correct. Take ad hominem fallacies for instance.

Person A is stupid, Person A makes statement B, Hence statement B is false.

Premis A and B maybe correct after testing. It doesn’t however follow that said statement is false by the virtue of those fallacies.

This falls under the part of my quote where I said “or the argument is invalid”. Even if Person A is stupid and makes B statement, ad hominem is a logically fallacy. In other words, it is a non sequitur. The conclusion does not follow from the premises.

Logical fallacy = invalid argument

QFT

This (below).

http://www.youtube.com/watch?v=3see39jS-fM

[Friedmanite]

I can’t believe the astonishing stupidity of some of the posters here. I mean

"A is C

B is C

Therefore A is B"

sounds like a valid argument to some of you dimwits? Jesus Christ.

[Seraiah]

sounds like a valid argument to some of you dimwits?

If a = c and b = c, then a = b is wrong in your mind. And you call me a dimwit?

I didn’t say a is like c, or b is like c, or a has attributes of c or… BAHHH. Do you two even speak English?

I said A IS C

[gotlucky]

See my post, Seraiah. What you have is an invalid argument.

[Seraiah]

If it makes you feel better it’s hereby ammended with what I obviously meant:

if A = B
And
C = B
Then
A=C

You leave out a damn comma around here and suddenly everyone becomes irrational hyperventilating monkeys.

@JackCuyler

Actually, you have that exactly backwards. It’s been true in testable, repeatable, observations because it’s true.

And what would the universe look like if it was like how I said it? Isn’t that a destinction without a difference?

[gotlucky]

It is still invalid. As I said before:

If Men are Humans.

And

If Women are Humans.

Then

Men are Women.

[Seraiah]

men =/= humans

woman =/= humans

men =/= woman

men is not synonomous with humans.

[Friedmanite]

Seriah, what I posted is the exact same, false argument you posted earlier. Look at it carefully.

[Friedmanite]

Oh and the fuck am I supposed to know what you “meant” when you put forth a logically invalid argument?

[Birthday_Pony]

“This statement is false.”

[gotlucky]

Friedmanite,

Actually, upon rereading Seraiah’s latest argument, it appears that he has actually switched his argument. Before he stated:

A is B

C is B

Therefore A is C.

But now he uses the “=” sign, which is “if and only if”.

So it appears that he has changed his argument, though I don’t think he realized it (neither did I, as I didn’t look closely when he restated it.) And Seraiah, I don’t know if you already knew this, but your original argument was, in fact, invalid.

Consider:

Socrates is a man.

We are not saying that Man = Socrates. We are saying that Socrates is in the category “men”. If this is not the way you intended to use the word “is”, then you should realize that your use is not how logicians treat that argument form.

[Friedmanite]

Gotlucky, an equals sign is most definitely not “if and only if”. The latter is a logical connective used with propositions. “Is” means equal, and to say that “A is B” or “A is equal to B” means that A and B are objects, not propositions.

[Torsten]

It is still invalid. As I said before:

If Men are Humans.

And

If Women are Humans.

Then

Men are Women.

That’s a category mistake. I think it’s only egalitarians that think as silly as that.

[gotlucky]

@Friedmanite

Gotlucky, an equals sign is most definitely not “if and only if”. The latter is a logical connective used with propositions. “Is” means equal, and to say that “A is B” or “A is equal to B” means that A and B are objects, not propositions.

I was taught to use ↔ for iff, but I was made aware that some people use = to mean that, not that we should. Anyway, it sounds like Seraiah is trying to say iff, even if he isn’t demonstrating it properly. His argument as he first stated it was certainly invalid, and I suppose you might be right about “=”, but I’ve heard that some people have used it to mean iff.