data/en/crtw_127.txt

Here are some examples of common fallacies:

### _ad hominem_

A theory is discarded not because of any evidence against it or lack of
evidence for it, but because of the person who argues for it. Example:

A: The Government should enact minimum-wage legislation so that workers are
not exploited.  
B: Nonsense. You say that only because you cannot find a good job.

### _ad ignorantiam (appeal to ignorance)_

The truth of a claim is established only on the basis of lack of evidence
against it. A simple obvious example of such fallacy is to argue that unicorns
exist because there is no evidence against such a claim. At first sight it
seems that many theories that we describe as scientific involve such a
fallacy. E.g. the first law of thermodynamics holds because so far there has
not been any negative instance that would serve as evidence against it. But
notice, as in cases like this, there is evidence for the law, namely positive
instances. Notice also that this fallacy does not apply to situations where
there are only two rival claims and one has already been falsified, then we
may justly establish the truth of the other even if we cannot find evidence
for or against it.

### _ad misericordiam (appeal to pity)_

In offering an argument, pity is appealed to. Usually this happens when people
argue for special treatment on the basis of their need. E.g. a student argues
that the teacher should let him/her pass the examination because he/she needs
it in order to graduate. Of course, pity might be a relevant consideration in
certain conditions, as in contexts involving charity.

### _ad populum (appeal to popularity)_

The truth of a claim is established only on the basis of its popularity and
familiarity. This is the fallacy committed by many commercials. Surely you
have heard of commercials implying that we should buy a certain product
because it has made to the top of a sales rank, or because the brand is the
city's "favourite".

### Affirming the consequent

Inferring that P is true solely because Q is true and it is also true that if
P is true, Q is true.

The problem with this type of reasoning is that it ignores the possibility
that there are other conditions apart from P that might lead to Q. For
example, if there is a traffic jam, a colleague may be late for work. But if
we argue from his being late to there being a traffic jam, we are guilty of
this fallacy - the colleague may be late due to a faulty alarm clock.

Of course, if we have evidence showing that P is the only or most likely
condition that leads to Q, then we can infer that P is likely to be true
without committing a fallacy.

### Begging the question ( _petito principii_ )

In arguing for a claim, the claim itself is already assumed in the premise.
Example: "God exists because this is what the Bible says, and the Bible is
reliable because it is the word of God."

### Complex question or loaded question

A question is posed in such a way that a person, no matter what answer he/she
gives to the question, will inevitably commit him/herself to some other claim,
which should not be presupposed in the context in question.

A common tactic is to ask a yes-no question that tricks people to agree to
something they never intended to say. For example, if you are asked "Are you
still as self-centred as you used to be?", then no matter you answer "yes" or
"no", you are bound to admit that you were self-centred in the past. Of
course, the same question would not count as a fallacy if the presupposition
of the question is indeed accepted in the conversational context.

### Composition (opposite of division)

The whole is assumed to have the same properties as its parts. Anne might be
humorous and fun-loving and an excellent person to invite to the party. The
same might be true of Ben, Chris and David considered individually. But it
does not follow that it will be a good idea to invite all of them to the
party. Perhaps they hate each other and the party will be ruined.

### Denying the antecedent

Inferring that Q is false just because if P is true, Q is also true, but P is
false.

This fallacy is similar to the fallacy of affirming the consequent. Again the
problem is that some alternative explanation or cause might be overlooked.
Although P is false, some other condition might be sufficient to make Q true.

Example: If there is a traffic jam, a colleague may be late for work. But it
is not right to argue in the light of a smooth traffic that the colleague will
not be late. Again, his alarm clock may have stopped working.

### Division (opposite of composition)

The parts of a whole is assumed to have the same properties of the whole. It
is possible that, on a whole, a company is very effective, while some of its
departments are not. It would be inappropriate to assume they all are.

### Equivocation

Putting forward an argument where a word changes meaning without having it
pointed out. For example, some philosophers argue that all acts are selfish.
Even if you strive to serve others, you are still acting selfishly because
your act is just to satisfy your desire to serve others. But surely the word
"selfish" means differently in the premise and the conclusion - when we say a
person is selfish we usually mean that he does not strive to serve others. To
say that a person is selfish because he is doing something he wants, even when
what he wants is to help others, is to use the term "selfish" with a different
meaning.

### False dilemma

Presenting a limited set of alternatives when there are others that are worth
considering in the context. Example: "Every person is either my enemy or my
friend. If he/she is my enemy I should hate him/her. If he/she is my friend I
should love him/her. So I should either love him/her or hate him/her."
Obviously, the conclusion is too extreme because most people are neither your
enemy nor your friend.

### Gambler's fallacy

Assumption is made to take some independent statistics as dependent. The
untrained mind tends to think that, e.g. if a fair coin is tossed five times
and the results are all heads, then the next toss will more likely be a tail.
It will not be, however. If the coin is fair, the result for each toss is
completely independent of the others. Notice the fallacy hinges on the fact
that the final result is not known. Had the final result been known already,
the statistics would have been dependent.

### Genetic fallacy

Thinking that because X dervies from Y, and Y has a certain property, X must
have the same property also. Example: "His father is a criminal, so he must
also be up to no good."

### _Non sequitur_

A conclusion is drawn which does not follow from the premise. This is not a
specific fallacy but a very general term for a bad argument. So a lot of the
examples above and below can be said to be non sequitur.

### _Petito principii_

Latin word for question begging.

### _Post hoc, ergo propter hoc_ (literally, "after this, therefore because of
this")

Inferring that X must be the cause of Y just because X is followed by Y.

For example, having visited a graveyard, I fell ill and infer that graveyards
are spooky places that cause illnesses. Of course, this inference is not
warranted since this might just be a coincidence. However, a lot of
superstituous beliefs commit this fallacy.

### Red herring

Within an argument some irrelevant issue is raised which diverts attention
from the main subject. The function of the red herring is sometimes to help
express a strong, biased opinion. The red herring (the irrelevant issue)
serves to increase the force of the argument in a very misleading manner.

For example, in a debate as to whether God exists, someone might argue that
believing in God gives peace and meaning to many people's lives. This would be
an example of a red herring since whether religions can have a positive effect
on people is irrelevant to the question of the existence of God. The good
psychological effect of a belief is not a reason for thinking that the belief
is true.

### Slippery slope

Arguing that if an opponent were to accept some claim C1, then he or she has
to accept some other closely related claim C2, which in turn commits the
opponent to a still further claim C3, eventually leading to the conclusion
that the opponent is committed to something absurd or obviously unacceptable.

This style of argumentation constitutes a fallacy only when it is
inappropriate to think if one were to accept the initial claim, one must
accept all the other claims.

An example: "The government should not prohibit drugs. Otherwise the
government should also ban alcohol or cigarettes. And then fatty food and junk
food would have to be regulated too. The next thing you know, the government
would force us to brush our teeth and do exercises everyday."

### Straw man

Attacking an opponent by attributing to him/her an implausible position that
is easily defeated when this is not actually the opponent's position.

Example: When many people argue for more democracy in Hong Kong, a typical
reply is to say that this is not warranted because it is wrong to think that
democracy is the solution to all of Hong Kong's problems, or to say that one
should not blindly accept democracy. But those who support democracy never
suggest that democracy can solve _all_ problems (e.g. pollution), and they
might also agree that _blindly_ accepting something is rarely correct, whether
it is democracy or not. Those criticisms attack implausible "strawman"
positions and do not address the real arguments for democracy.

### Suppressed evidence

Where there is contradicting evidence, only confirming evidence is presented.

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