Logical Fallacies


 * Study this list to prevent others from making fallacious arguments against you.
 * Despite the fact these are fallacies, they are often good tools for argument (an argument can be won by embarrasing your opponent ("You're a thief though!") or other well placed fallacies).
 * Therefore, knowing how to use these effectively or in a non-fallacious form is just as important as preventing opponents from using them.
 * Avoid in discussions where both sides are being intellectually honest.
 * Note the full form of each argument is "Argument to" or "Argumentum ad..."
 * Using the latin the correct circumstances sounds intelligent and credible and is damning for the opposition, in the wrong circumstances pretentious
 * Note that even if a premise and conclusion are true, the argument may still be fallacious.
 * What follows is not complete list of fallacies, but rather those that may be used somewhat often and are useful to spot in an argument, because they may not be as obvious, or people will have a hard time "putting their finger" on the fallacy

Ad Hominem (To the Person)
In general a response about the person making the argument instead of about the actual logical progression of the argument itself. It has a few forms:

Abusive
Saying that the person making the argument is a bad person. For example, the following would be fallacious


 * Hitler says murder is wrong, so murder must be right.
 * Mengele says murder is right, so murder must be wrong.
 * Jane says that liver transplants for alcoholics are good, but we shouldn't listen to her because she has used cocaine.

Note that in the second case, while the conclusion is (generally accepted to be) true, the argument itself is fallacious.

Circumstantial
Claiming that a person/entity has a bias, therefore their argument must be wrong

The following are fallacies:


 * Tobacco companies argue that people have the right to smoke, but they only say that because they make money when people smoke. Ignore their argument.
 * You're too young to vote, what do you know about politics?
 * He used to be poor and he says the poor need more money, but you have never been poor and you say they don't. But you can't possibly understand the plight of the poor so he must be right.

The following is not a fallacy:


 * A Tobacco company funded that study, so we shouldn't trust its results. (Studies have shown that studies are, in fact, biased. Accusing someone of lying because of their bias is not a fallacy, so long as you do not dismiss their argument)

Tu Quoque
Hypocrisy does not dismiss an argument. The following are fallacies:


 * He says people should conserve energy but he doesn't do it himself, don't listen to his argument. (Nevertheless, feel free to kritik the environmental movement or generally ridicule Al Gore.)
 * He says that stealing is wrong but he is a thief! Ignore his argument

Association Fallacy
Also known as "Guilt by Association" fallacy

Saying that someone's arguments are in line with some other person or group, therefore they are a member of that group.

Fallacies courtesy Wikipedia:


 * You say the gap between the rich and poor is unacceptable, but communists also say this, therefore you are a communist
 * You say the gap between the rich and poor is unacceptable, but communists also say this, and they believe in revolution. Thus, you believe in revolution.

Note that in some cases it may be possible to show that if the person is logically consistent, they do believe in revolution or the equivalent example

Inverse
Claiming something/someone's argument is true because they are a good person.


 * He seems to be an upstanding gentleman, he must be right about murder being justified.

This may also take the form of an Ad Vercundiam

Ad Vercundiam (Appeal to Authority)
Claiming that because a celebrity says something it is true.

A classic example is celebrity endorsements, which try to invoke an Ad Vercundiam


 * Tiger Woods says these clubs are the best for me, he must be right
 * President Obama says 2+2=5, he must be right
 * The bible says murder is wrong, therefore murder is wrong (The bible may be correct because it is a perfect statement of the moral code, but then murder is wrong because it violates this moral code. The statement by itself is fallacious)
 * Ditto for Jesus
 * Thomas Jefferson said people have the inalienable rights, therefore they do.
 * Ditto for The US Constitution
 * A well reputed poll service or news service says so, therefore it is true.
 * My teacher or doctor said so, therefore it is true
 * A Majority of scientists say so, therefore it is true

Note that while the conclusions may be true, and the premise may be true, the above arguments are all still fallacious. If the conclusion is true then one must show it is true by non-fallacious means (e.g. debating the actual science or studying poll methodology)

Ad Populum (Appeal to the People)
also literally from Latin "Appeal to the Nation" In essence, popular opinion is irrelevant

Other names:
 * Appeal to the masses,
 * Appeal to belief
 * Appeal to the majority
 * Appeal to the people
 * Argument by consensus
 * Authority of the many
 * Bandwagon fallacy


 * Ad numerum
 * Consensus gentium


 * 9 out of 10 people oppose the Iraq war, therefore it is a bad policy (Possible to show if you can show democracy is the value. It's not though)
 * Anything with "Everyone knows"
 * Most people have no problem eating meat, therefore its ethical
 * "Every society but ours believed in magic; why should we think otherwise?" "Every society but ours thought the sun revolved about the Earth, rather than the other way round. Would you decide the matter by majority vote?" - Isaac Asimov.
 * Everybody smokes pot, it can't be bad for you and I won't get caught

Ad Antiquitatem (Appeal to Tradition)
Also know as "Appeal to Common Practice," or the "is/ought fallacy"

The fallacious argument is any one that runs "things have always been done this way therefore..."

Examples:


 * We've used the US Constitution for 200+ years, we shouldn't stop now
 * Slavery has existed in every society, so it can't be bad (or we shouldn't stop it)
 * All societies have(n't) had homosexuality, therefore it is(n't) ok
 * Mankind has always had wars, if we stop then mankind will cease to exist

Appeal to Emotion
Any logical fallacy which appeals to people's emotions (non-rational/logical selves). It encompasses:
 * Appeal to Consequences
 * Appeal to Fear
 * Appeal to Flattery
 * Appeal to Pity
 * Appeal to Ridicule
 * Appeal to Spite
 * Appeal to Consequence of belief

Ad Consequentiam (Appeal to Consequences)
Much like appeal to consequence of a belief (below), this fallaciously states that a premise is true because the consequence is desirable, or vice versa, that the premise is false because the consequences is not desirable.


 * If my proof were true, it would prove the Riemman Hypothesis, therefore my proof is true.
 * If home prices go up, people will be happy, therefore home prices will go up.
 * If it is impossible to travel at faster than light speed, then human expansion will be limited and the human race will die out. Therefore it is possible to travel faster than light speed.

Ad Baculum (Appeal to Force)
Any Ad Consequentiam where the consequence is the use of force etc.

For example:


 * If you don't believe in God, you will go to hell. Therefore you should believe in God.
 * Racism is wrong because you will be sent to jail if you act on it
 * If you don't give me money, I will beat you up. Therefore you should give me money

Appeal to Fear
Setting up a dichotomy (false or no), and pointing out that someone should fear one option.

It often has a form:

Either P or Q is true. Q is frightening. Therefore, P is true.

For example:


 * You shouldn't say such things against liberalism! If a teacher heard what you were saying, you would never receive a good grade. So, you should learn that it is wrong to speak out against it.
 * You shouldn't believe homosexuality is morally wrong, if somebody found out, you might get kicked out of school. Ergo, you should believe there is nothing wrong with it.

Appeal to Flattery
A form of appeal to consequences

Appeal to Pity

 * "Hire me because I will starve if you don't"
 * If you don't vote for the medicare bill, people won't be able to get their disease cured, therefore the medicare bill is good.

Appeal to Ridicule
Also known as The Horse Laugh or Appeal to Mockery


 * "2+2=5!? That's ridiculous"
 * "Black men can fly planes!? That's ridiculous"

Appeal to Spite
Courtesy Wikipedia:


 * "By voting for my proposal instead of Jim's, you'll finally have a chance to get back at him for running over your dog!"
 * "Bill Gates dumped you back in high school. Therefore you should never buy any Microsoft products."

Appeal to Consequences of a Belief
Also know as "Wishful Thinking"


 * The statement that if people believed A, there would be consequences, therefore A
 * Or the inverse, if people believed in B, there would be negative consequences, therefore not B
 * Or another inverse, if people did not believe in A, there would be negative consequences, therefore A
 * etc.

Examples of fallacies:


 * If people didn't believe God existed, the world would be a much worse place, therefore God exists.
 * If we believe there could be a nuclear war, we would be so scared we would die, therefore there will be no nuclear war
 * If everybody believed that Obama would heal the earth, everybody would be happier and the world would be a better place, therefore Obama will heal the earth

Examples of non-fallacies:


 * If I believe God exists, everybody's life will be better. Therefore I should believe God exists. (The key word is 'should.' However, a statement's truth is independent of whether or not everyone should believe something)

Ad Novitatem (Appeal to Novelty)

 * The most recent study shows that carbs are good for losing weight, therefore carbs are good for losing weight. (Instead debate the merits of the studies)
 * My computer is only 1 year old, yours is 2 years old. Therefore mine is better.
 * Upgrade to Windows Vista(TM)!