sordavie

Further along those lines. We call it an informal fallacy because it's useful to make distinctions when studying these things. The argument there is also guilty of a formal fallacy, if there is such a thing.

We could just be very rough and label all arguments either "good" or "bad" without regard to how, specifically, it goes wrong. This is what I see you wanting to do, just not quite as roughly.

Informal fallacies came out of the study of informal logic. Informal logic started out as an educational development - a way to teach students how to analyze ordinary everyday arguments. Critical thinking courses were designed in such a way so that no formal logic was taught. Instead the cirriculum revolved around informal logic. This is why there's overlap. The relationship between informal logic and formal logic is pretty complicated. It's not as if a bad argument is (exclusively) either a formal or informal fallacy. Really there is no talk about fallacies in formal logic. We talk about validity, unvalidity, soundness, and unsoundness among other things.

Background on informal logic: http://plato.stanford.edu/entries/logic-informal/
Background on formal logic: http://plato.stanford.edu/entries/logic-classical/

__________________

CingularDuality

But you see, you've made Sordavie's point. Your "rational belief" is not based on the fact that "there's no evidence that UFOs don't exist". Your belief is probably based on statistical evidence based on human knowledge of the supposed infiniteness of the universe, which is quite a different argument from "there's no evidence that UFOs don't exist".

__________________

Become a supporting member!

Buy a Tactical Duck!
Take the world's smallest political quiz! "I was touched by His Noodly Appendage."
TacticalGamer TX LAN/BBQ Veteran:

Switchcraft

I'm a little concerned with your characterization of that argument as sound. Validity only guarantees that IF all of the premises of the argument are true, THEN the conclusion must be true. In order for the argument to be "sound" the premises actually have to be true. In this case, I think we could all be convinced there are other things to do with stolen money besides buy a new car.

Steeler

The logic is not sound, because your only given is that there is a causal relationship from A to B. There is no given stating if B, then A. Therefore the state of B is immaterial to the state of A. This would only work in a completely closed system with no further variables.

This would work:

Given: Only if A, then B
Given: Not B
Therefore: Not A

__________________

Switchcraft

Steeler, for the purposes of describing a logical syllogism, his argument as written was valid. (A valid argument being an argument constructed so that as long as the first two premises were true, the conclusion had to be true.) Your argument seems correct, but it's why I failed my first logic exam in college.

The easy way to prove it is to use premises you know to be true in place of the variables.

If A then B. (If it's a tiger, then it's a cat)
Not B. (It's not a cat.)
Therefore not A (There for it's not a tiger.)

The argument is valid because as long as you substitute true premises for the first two premises, the conclusion will always be true.

icky

How to spot a bad argument? Just look in this thread.

__________________
Peace through fear... since 1947!

Steeler

Ok, I can see how that would work for provable absolutes. It's when you calculate your outcomes without proving your premises that your case falls apart. But that's true of any argument. Thanks Switch.

__________________

xTYBALTx

What? It's true for any argument.

If A then B.
Not B.
Therefore not A.

If I went to Venus, I burned to death in a fiery ball of plasma.
I did not burn to death in a fiery ball of plasma.
Therefore, I did not go to Venus.

Or is that too provable and absolute?

If I was kidnapped by aliens, I'd have a chip implanted in my eyeball.
I do not have a chip implanted in my eyeball.
Therefore, I was not kidnapped by aliens.

If SWAT4 sucks, my mind is orange.
My mind is not orange.
Therefore, SWAT4 does not suck.

It's deductive logic. Like math, only for deductive arguments. Works for any deductive argument: provable, unprovable, absolute, not-absolute, green, black, tiger-striped, whatever. Note, please, that an argument does not have to be sound to be logically valid! See argument three, the one about my mind being orange, for an example of an unsound - but valid! - argument.

I have no idea whath your second sentence is supposed to mean. In fact, I don't know what a provable absolute is supposed to be. But if you want to prove the basic rules of logic wrong, well...you might want to take an introductory logic course first. :]

__________________
A policy of freedom for the individual is the only truly progressive policy. -F.A. Hayek

Steeler

Calm down. I understand now. But we are blending logic with rhetorical argument, and that is the source of confusion. In rhetoric, people often let a logically invalid statement stand without challenging its premises.

__________________

Buck Fush

You all got it wrong. To spot a bad argument just look <--over there and see if it says "leejo" next to it.

jk leejo, you've bested me too many times to really believe that.

Rincewind

I think the real lesson here is not to argue in a thread that defines what a poor argument is.



You beat me to it All of my <3 to leejo.

__________________
~~ Veritas simplex oratio est ~~
No matter how far a wizard goes, he will always come back for his hat. --T. Pratchett

<---- You know you're getting old when you rely on your forum meta-data to remind you how old you are.

Required Reading for all TG sandboxers

xTYBALTx

Steeler - I don't appreciate your tone. Nor do I understand what you mean when you reference "blending logic with rhetorical argument."

__________________
A policy of freedom for the individual is the only truly progressive policy. -F.A. Hayek

Steeler

I wasn't aware that my tone was in error. I don't know what I said to set you off, Tybalt, but you sound a lot more aggressive here than I thought was warranted. I meant that in this thread we are talking about two different aspects of communication. Notably, formal logic, which is inscrutable to many and has it's own language and forms of explanation. The other is rhetoric, in which knowledge of logical fallacy is only one of many tools available to a person attempting to influence the outcome of a debate.

__________________

Mateo

Oh SNAP!

xTYBALTx

Aggressive? "Set me off"? What? I have no idea what you're talking about.

__________________
A policy of freedom for the individual is the only truly progressive policy. -F.A. Hayek