Logic 101

El_mariachi

I little logic, I found is sorely needed in the fourm.
shamelessly ripped from http://www.theskepticsguide.org/logicalfallacies.asp

What is a logical fallacy?
All arguments have the same basic structure: A therefore B. They begin with one or more premises (A), which is a fact or assumption upon which the argument is based. They then apply a logical principle (therefore) to arrive at a conclusion (B). An example of a logical principle is that of equivalence. For example, if you begin with the premises that A=B and B=C, you can apply the logical principle of equivalence to conclude that A=C. A logical fallacy is a false or incorrect logical principle. An argument that is based upon a logical fallacy is therefore not valid. It is important to note that if the logic of an argument is valid then the conclusion must also be valid, which means that if the premises are all true then the conclusion must also be true. Valid logic applied to one or more false premises, however, leads to an invalid argument. Also, if an argument is not valid the conclusion may, by chance, still be true.
Top 20 Logical Fallacies (in alphabetical order)
1. Ad hominem An ad hominem argument is any that attempts to counter anothers claims or conclusions by attacking the person, rather than addressing the argument itself. True believers will often commit this fallacy by countering the arguments of skeptics by stating that skeptics are closed minded. Skeptics, on the other hand, may fall into the trap of dismissing the claims of UFO believers, for example, by stating that people who believe in UFO's are crazy or stupid.
2. Ad ignorantiam The argument from ignorance basically states that a specific belief is true because we don't know that it isn't true. Defenders of extrasensory perception, for example, will often overemphasize how much we do not know about the human brain. UFO proponents will often argue that an object sighted in the sky is unknown, and therefore it is an alien spacecraft.
3. Argument from authority Stating that a claim is true because a person or group of perceived authority says it is true. Often this argument is implied by emphasizing the many years of experience, or the formal degrees held by the individual making a specific claim. It is reasonable to give more credence to the claims of those with the proper background, education, and credentials, or to be suspicious of the claims of someone making authoritative statements in an area for which they cannot demonstrate expertise. But the truth of a claim should ultimately rest on logic and evidence, not the authority of the person promoting it.
4. Argument from final Consequences Such arguments (also called teleological) are based on a reversal of cause and effect, because they argue that something is caused by the ultimate effect that it has, or purpose that is serves. For example: God must exist, because otherwise life would have no meaning.
5. Argument from Personal Incredulity I cannot explain or understand this, therefore it cannot be true. Creationists are fond of arguing that they cannot imagine the complexity of life resulting from blind evolution, but that does not mean life did not evolve.
6. Confusing association with causation This is similar to the post-hoc fallacy in that it assumes cause and effect for two variables simply because they are correlated, although the relationship here is not strictly that of one variable following the other in time. This fallacy is often used to give a statistical correlation a causal interpretation. For example, during the 1990’s both religious attendance and illegal drug use have been on the rise. It would be a fallacy to conclude that therefore, religious attendance causes illegal drug use. It is also possible that drug use leads to an increase in religious attendance, or that both drug use and religious attendance are increased by a third variable, such as an increase in societal unrest. It is also possible that both variables are independent of one another, and it is mere coincidence that they are both increasing at the same time. A corollary to this is the invocation of this logical fallacy to argue that an association does not represent causation, rather it is more accurate to say that correlation does not necessarily mean causation, but it can. Also, multiple independent correlations can point reliably to a causation, and is a reasonable line of argument.
7. Confusing currently unexplained with unexplainable Because we do not currently have an adequate explanation for a phenomenon does not mean that it is forever unexplainable, or that it therefore defies the laws of nature or requires a paranormal explanation. An example of this is the "God of the Gapsâ" strategy of creationists that whatever we cannot currently explain is unexplainable and was therefore an act of god.
8. False Continuum The idea that because there is no definitive demarcation line between two extremes, that the distinction between the extremes is not real or meaningful: There is a fuzzy line between cults and religion, therefore they are really the same thing.
9. False Dichotomy Arbitrarily reducing a set of many possibilities to only two. For example, evolution is not possible, therefore we must have been created (assumes these are the only two possibilities). This fallacy can also be used to oversimplify a continuum of variation to two black and white choices. For example, science and pseudoscience are not two discrete entities, but rather the methods and claims of all those who attempt to explain reality fall along a continuum from one extreme to the other.
10. Inconsistency Applying criteria or rules to one belief, claim, argument, or position but not to others. For example, some consumer advocates argue that we need stronger regulation of prescription drugs to ensure their safety and effectiveness, but at the same time argue that medicinal herbs should be sold with no regulation for either safety or effectiveness.
11. The Moving Goalpost A method of denial arbitrarily moving the criteria for "proof" or acceptance out of range of whatever evidence currently exists.
12. Non-Sequitur In Latin this term translates to "doesn't follow". This refers to an argument in which the conclusion does not necessarily follow from the premises. In other words, a logical connection is implied where none exists.
13. Post-hoc ergo propter hoc This fallacy follows the basic format of: A preceded B, therefore A caused B, and therefore assumes cause and effect for two events just because they are temporally related (the latin translates to "after this, therefore because of this").
14. Reductio ad absurdum In formal logic, the reductio ad absurdum is a legitimate argument. It follows the form that if the premises are assumed to be true it necessarily leads to an absurd (false) conclusion and therefore one or more premises must be false. The term is now often used to refer to the abuse of this style of argument, by stretching the logic in order to force an absurd conclusion. For example a UFO enthusiast once argued that if I am skeptical about the existence of alien visitors, I must also be skeptical of the existence of the Great Wall of China, since I have not personally seen either. This is a false reductio ad absurdum because he is ignoring evidence other than personal eyewitness evidence, and also logical inference. In short, being skeptical of UFO's does not require rejecting the existence of the Great Wall.
15. Slippery Slope This logical fallacy is the argument that a position is not consistent or tenable because accepting the position means that the extreme of the position must also be accepted. But moderate positions do not necessarily lead down the slippery slope to the extreme.
16. Straw Man Arguing against a position which you create specifically to be easy to argue against, rather than the position actually held by those who oppose your point of view.
17. Special pleading, or ad-hoc reasoning This is a subtle fallacy which is often difficult to recognize. In essence, it is the arbitrary introduction of new elements into an argument in order to fix them so that they appear valid. A good example of this is the ad-hoc dismissal of negative test results. For example, one might point out that ESP has never been demonstrated under adequate test conditions, therefore ESP is not a genuine phenomenon. Defenders of ESP have attempted to counter this argument by introducing the arbitrary premise that ESP does not work in the presence of skeptics. This fallacy is often taken to ridiculous extremes, and more and more bizarre ad hoc elements are added to explain experimental failures or logical inconsistencies.
18. Tautology A tautology is an argument that utilizes circular reasoning, which means that the conclusion is also its own premise. The structure of such arguments is A=B therefore A=B, although the premise and conclusion might be formulated differently so it is not immediately apparent as such. For example, saying that therapeutic touch works because it manipulates the life force is a tautology because the definition of therapeutic touch is the alleged manipulation (without touching) of the life force.
19. Tu quoque Literally, you too. This is an attempt to justify wrong action because someone else also does it. "My evidence may be invalid, but so is yours."
20. Unstated Major Premise This fallacy occurs when one makes an argument which assumes a premise which is not explicitly stated. For example, arguing that we should label food products with their cholesterol content because Americans have high cholesterol assumes that: 1) cholesterol in food causes high serum cholesterol; 2) labeling will reduce consumption of cholesterol; and 3) that having a high serum cholesterol is unhealthy. This fallacy is also sometimes called begging the question.


More to come!

No More , we believe you !!

monkeyfudge

El_mariachi

More like

Haven't broken out this bad boy yet:
Stanford Encyclopedia of Philosophy

Oryx

Im still digesting that post, but this sentence sticks:

The structure of such arguments is A=B therefore A=B, although the premise and conclusion might be formulated differently so it is not immediately apparent as such

. If A=B, then inarguably, A=B. Or am I not grasping your point here?

???

An example is God exists because God created man therefore creationism is true because God created man.

Riamfada

??? wrote: »

An example is God exists because God created man therefore creationism is true because God created man.

Yeah you know it is

lotsapockets

Here is the question that caused be to be ejected from catechism class when I was a child. If everything exists because God created it, then would it be fair to say nothing can exist without being created? If so who created God?

???

Agreed!!! Though that is a logical falacy! There is no reason that a 'creator' couldn't have evolved! (Though don't suggest it, it doesn't go down well!)

I was just using it as an example of a tautology. Religon is the big area you find tautologies.

Eschatologist

??? wrote: »

An example is God exists because God created man therefore creationism is true because God created man.

Lol! Sure just head on over to the Bible, Creationism and Prophecy thread to see most of these fallacies in action :pac:

Sad but true.

johnsix

Though I should continue this.
Still sorely needed.

http://en.wikipedia.org/wiki/Burden_of_proof#Science_and_other_uses

http://en.wikipedia.org/wiki/Negative_proof

Take for example, I state there is a large purple dragon in my sitting room. Your logically default position for such a ridiculous claim is "no, there is not a dragon in the sitting room."
Before it can even be considered to be possible some evidence must be shown, say a picture or what not.
Still more proof is required before the dragon can be said for certain to be in the sitting room, say actually producing the dragon.

It true that "A supernatural force does not exist, because there is no proof that it does exist." is a logical fallacy, the reverse "A supernatural force must exist, because there is no proof that it does not exist", is also a fallacy.
To continue the example.
Say I bring you home to show you the dragon. However you see no dragon in the sitting room. My excuse is that the dragon is invisible. You suggest touching the dragon and feeling its shape to prove it's existance. I, however say the dragon is intangible as well. You next suggest using a thermal camera to detect the dragons fire breath. I say that unfortunately the dragon breathes room temperature fire. And so on.
Given that all proposed experiments cannot detect the dragon, there are other more likely explanations than a large undetectable dragon is actually there.
The first explanation, and most likely one, is that I simply am lying.
Second, I am mentally ill.
Thrid, and least likely, is that someone is playing an elaborate and cruel trick on me, using various methods to convince me there is a dragon there.
All of these are much, much more likely then there actually being a dragon in my living room.

As for the paranormal, proposed experiments either don't work or wouldn't work. And there has always been a much more likely explanation for paranormal phenomenon.
So baring actual evidence of it, it is reasonable to assume that there is no supernatural forces.

johnsix

http://en.wikipedia.org/wiki/Scientific_method
http://www.freeinquiry.com/intro-to-sci.html

For all those who go on paranormal "investigations"

Riamfada

Ive wasted my life :eek:

johnsix

Grimes wrote: »

Ive wasted my life :eek:

So you don't use the scientific method?
No wonder....

Riamfada

Well Johnsix. My main method of obtaining recordings is to bring my grandmother with me when I am trying to capture EVP. Shes very good, whenever she is there I always get a rhaspy low voice on my recordings. Secondly I like to throw things and then pretend its poltergeist activity. I believe Im a scientific researcher and that every other part time paranormal enthusiast is pathetic for not holding high standard qualifications and obtaining tenure for massive research into paranormal research.

RANK AMATURES!

Its just you and me johnsix. Only we know the definitive secrets of the universe.

johnsix

Grimes wrote: »

I believe Im a scientific researcher and that every other part time paranormal enthusiast is pathetic for not holding high standard qualifications and obtaining tenure for massive research into paranormal research.

So you needs these things to apply the scientific method.... because?
It's honestly not that hard.

Then again the more it's applied to paranormal research, the results seems a little less paranormal.
Funny that.

Riamfada

johnsix wrote: »

Then again the more it's applied to paranormal research, the results seems a little less paranormal.
Funny that.

Well if we found ghosts then what would you have to post about eh? Research dosnt always prove exactly what you want it to prove. Proving the non existence of the paranormal is just as good as have a ghost spurt its ectoplasm in your face in my eyes. I just try to weigh up the facts from both sides of the arguement rather than linking to wikipedia. The most unreliable source, a clearly unscientific method imo.

???

Disagree with you there. http://npg.nature.com/nature/journal/v438/n7070/full/438900a.html

johnsix

Grimes wrote: »

Well if we found ghosts then what would you have to post about eh? Research dosnt always prove exactly what you want it to prove. Proving the non existence of the paranormal is just as good as have a ghost spurt its ectoplasm in your face in my eyes. I just try to weigh up the facts from both sides of the arguement rather than linking to wikipedia. The most unreliable source, a clearly unscientific method imo.

Who said linking to wikipedia was scientific?
I link to wikipeida because it is concise and gives a good starting point on many subjects like this: http://en.wikipedia.org/wiki/Ad_hominem.

The results of scientific research are independent of what you want to prove it just show the facts.

If you read the other posts in this thread you'd see that you can't prove a negative. I can't prove 100% the is no such thing as the paranormal. It is up to the claimant to show evidence, I can refute said evidence through logic and counter-evidence.

I'd be perfectly happy with saying I was wrong about the paranormal, but I'm not going to say that without some good solid proof.