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Logical Fallacies

Some explanations and examples. A work in progress.

Roberto Ruiz

on 26 March 2017

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Transcript of Logical Fallacies

Ad hominems
(Genetic fallacies)
Causal Fallacies
Fallacies of

Distracting Appeals
The Importance
of Spelling

Straw Man
Abusive ad hominem
ad hominem
Appeal to
Poisoning the well
Tu quoque
(appeal to popularity)

Appeal to
Appeal to emotion
Questionable cause
Cum hoc
ergo propter hoc

Slippery slope
(also known as
False dilemma,
or the
Either/Or fallacy)
Appeal to

Argument from
personal incredulity
Begging the question
Complex question
Naturalistic Fallacy
(aka the appeal to nature,
or the is/ought fallacy).
Faulty analogy
Appeal to tradition
Special pleading
Post hoc
ergo propter hoc
Informal Logical Fallacies
Have you
finally stopped
gay porn?
If evolution were true, then we would be no better than monkeys. Therefore, it must be false.
"If they don't have the guts to come up here
in front of you and say,
'I don't want to represent you,
I want to represent those special interests,
the unions, the trial lawyers ...
if they don't have the guts,
I call them girlie men."
Man: I believe in equality... if it's okay for men to walk outside topless, then it should also be okay for women to do the same.

Woman: You're just saying that because you want to see boobs...
Fallacies of

Fallacies of Relevance
Fallacies of relevance
are instances of reasoning in which
an argument relies on premises
that are not relevant to the conclusion,
and therefore cannot establish its truth.

In the case of red herrings, an irrelevant topic
is presented in order to divert attention
from the original issue.
[Joe McCarthy] announced that he had penetrated "Truman's iron curtain of secrecy" and that he proposed forthwith to present 81 cases... Cases of exactly what?

"I am only giving the Senate," he said, "cases in which it is clear there is a definite Communist connection… persons whom I consider to be Communists in the State Department."

…Of Case 40, he said, "I do not have much information on this except the general statement of the agency… that there is nothing in the files to disprove his Communist connections."
When it is argued that a proposition is true
simply on the basis that is has not been proved false,
(or that it is false because it has not been proved true).

In other words, this type of fallacious argument uses
an admitted ABSENCE of evidence to pass off as ACTUAL evidence.

This fallacy also occurs when the party making a claim
asks his/her opponent to
the conclusion.
If the conclusion is not disproved,
the claim is then mistakenly asserted to be true on that basis.

In reality, however, the person making the affirmative claim
is the one who has the burden of proof, not the skeptic.

If a claim does not satisfy your standards of evidence,
you have every right not to accept it.
An argument in which one attempts
to defend oneself or another from criticism
by turning the critique back against
the accuser or some other party
(the classic children's response:
"but she started it!"


by arguing that a proposition must be false
because the behavior of the person proposing it
is inconsistent with her proposition
(the other classic response:
"look who's talking"

A person's lack of
credibility does not automatically invalidate
the truth
of her claims
the merits

of her arguments.
To poison the well is to commit a pre-emptive ad hominem strike
against an argumentative opponent,
usually formulating the attack in such a way that,
whatever the opponent says, it will somehow 'confirm' the pre-emptive strike.

If the well of discourse is poisoned from the outset
(even without the introduction of an ad hominem),
any water drunk from it will taint the audience's conclusions.

If a case is so stated that contrary evidence is automatically precluded
(thus rendering it as an untestable or unfalsifiable claim),
no argument against it can be offered,
not because the charge is necessarily true
but because it's ultimately meaningless.

An easy way to spot this kind of fallacy is to notice that
any evidence one could potentially present against the original charge
can always be re-interpreted to be consistent with the original claim.

Philosophers sometimes argue that such claims
are so bad that they are
"not even wrong."
A complex, or "loaded" question,
like a loaded gun, is a dangerous thing.
A complex/loaded question is a question or an idea
which contains a buried presupposition,
usually either false or questionable,
and it is "loaded" with that presumption.

The appropriate thing to do when confronted with such cases
is to expose the hidden presupposition,
split it from the explicit charge, and
provide an independent answer to each of the claims.
Native Americans are disappearing.
Oh no! The dancing man in the picture
is a Native American.
He's about to disappear!
Accent is a fallacy of
(the study of how speech is used),
not of semantics
(the study of meaning) like equivocation,
not of syntax
(the study of structure) like amphiboly.

It takes place when a shift of meaning arises (or could arise) as a consequence
of changes in the vocal emphasis and tone given to its words or parts.

As with the previous examples, when reading an instance of this fallacy,
the meaning of the phrase may seem ambiguous, and the ambiguity disappears only once you say it out loud.

The problem, however, consists in figuring out
to read the phrase out loud.
On what non-arbitrary basis can we make such a determination, especially in cases when we don't have the proper context to understand the intended meaning of a phrase?

Keep in mind that how you say something out loud can be determined by how the phrase in question is punctuated.

The fallacy of accent, therefore, can often be a consequence
of improper punctuation, which may itself be a function of context.
The accent fallacy can also be committed
when the meaning of a quoted passage
is distorted by pulling said passage
out of context.

When done deliberately,
this is also known as
quote mining.
Equivocation is a
semantic fallacy

It occurs when the meaning of the same word or phrase
changes between different parts of the same argument,

or when different speakers use the same word in a discussion without realizing that each of them mean something different by the same word.
Amphiboly is a
fallacy of syntax
(that is to say, one based on grammatical structure).

It occurs when a bad argument trades upon
grammatical ambiguity to create an illusion of cogency:
Instead of using the same word with multiple meanings
(as with equivocation), amphiboly involves the use of
which can be interpreted in multiple ways
with equal justification.

An amphiboly is an ambiguity which results from
ambiguous grammar and awkward phrasing.
If those who cut people with knifes are criminals,
and surgeons cut people with knives for a living,
then surgeons are professional criminals!
Stay away from them!
This fallacy occurs
when one applies a general rule
to those exceptional cases
in which the rule does/should apply.

The problem with a sweeping generalization
is that we move too quickly
from a generalization
to a particular claim.
Always remember
to proofread your work!
Those people can't complain that war is indecent
because they themselves are indecent!
Why did you guys decide to dress up like that?
Oh, because everyone else is... duh!
What does this mean?

This fallacy is committed
when one assumes in the premises
of an argument
the very point that the argument
is supposed to prove.

In other words,
begging the question is

This video contains profane language, as well as multiple logical fallacies.
Your moral and/or intellectual sensibilities might be offended.
Of course, when you say things like that, someone is bound to make fun of you...

The God
of the Gaps
Stop the slaughter of animals!
Every year, as the rate of ice cream consumption increases, the rates of drowning and theft increase too.
Therefore, we should ban ice cream from our city, as this scourge of evil will destroy our civilization!
Explanation of the non-causal correlation
The fact that ice cream consumption and theft are CORRELATED with each other doesn't necessarily mean that there is a CAUSAL relationship between them.
In this case, the cause for both is a third factor: the summer heat.
Although his music may have been heavenly,
this argument fails to establish the conclusion
(that Ray Charles is God) because,
as Bill Clinton taught us:

In other words, one sense of
is that of
(meaning 'identical with'):

"Ray Charles is identical with God."

The other sense of "is" is that of
predicate attribution
(meaning 'has the quality of'):

"Ray Charles has the quality of being blind"
(but not "Ray Charles is identical with blindness").

This argument would work only if "is" were used
in every instance as an identity relation.
This fallacy turns on an ambiguity between the 'distributive' and the 'collective' use or meaning of general terms.
Fallaciously reasoning
from the attributes of a whole
to the attributes of its parts,

or from the attributes of a collection
to the attributes of the members of said collection.
Bill: You know, those feminists all hate men.
Joe: Really?
Bill: Yeah. I was in my philosophy class the other day
and that Rachel chick gave a presentation.
Joe: Which Rachel?
Bill: You know her. She's the one that runs that feminist group over at the
Women's Center. She said that men are all sexist pigs. I asked her why she
believed this and she said that her last few boyfriends were real sexist pigs. "
Joe: That doesn't sound like a good reason to believe that all of us are pigs.
Bill: That was what I said.
Joe: What did she say?
Bill: She said that she had seen enough of men to know we
are all pigs. She obviously hates all men.
Joe: So you think all feminists are like her?
Bill: Sure. They all hate men.
Does it mean this?
When is it okay to use analogies?
Of course, things can get complicated quite quickly...
Remember that, as Bertrand Russell once said,

"The fact that an opinion has been widely held

is no evidence whatever that it is not utterly absurd.

Indeed in view of the silliness of the majority of mankind,

a widespread belief is more likely to be foolish

than sensible."
Did you also catch the instances (used or mentioned) of

abusive ad hominem
faulty analogy
circumstantial ad hominem
appeal to inappropriate authority
appeal to emotion
questionable cause
"teach the controversy"?

Or did you only see the fallacy you were originally looking for?

Remember, critical thinking requires
permanent vigilance
This fallacy occurs when a person or group makes itself a special exception
(without any rational justification)
to the reasonable application of standards, principles, or expectations that normally apply
to everyone else,

or, conversely, when a person or group argues (again, without any rational justification)
that the same standards, principles, or expectations that normally apply to everyone, should not apply to a particular person or group.

The problem with this way of thinking is the introduction of
an unjustified double standard
"Teach the Controversy"
Explanation / Analysis

Just because can't figure out the answer to some mystery
doesn't mean that there isn't a perfectly normal, natural explanation for it.

An absence of knowledge or understanding
gives us NO justification in reaching a conclusion,
especially one that's to everyday experience.
An English Professor wrote
the following sentence on the board:

"A woman without her man is nothing."

He then asked his students to punctuate it correctly.

All the males in the class wrote:
"A woman, without her man, is nothing."

All the females in the class wrote:
"A woman: without her, man is nothing."

Punctuation is more powerful
than you may normally realize...
These are the best basketball players in the world.
If we recruit them all into the same team,
we'll have the best team in the world!
The 2004 Dream Team
Fallaciously reasoning
from the attributes of the parts of a whole
to the attributes of the whole itself,

or from the attributes of the individual elements of a collection
to the attributes of the collection or totality of those elements.
Learning not to jump to post hoc conclusions.
In this type of argument, it is fallaciously argued that

one's own inability to solve a mystery,
understand a phenomenon or process,
or figure out the solution to a problem,

somehow warrants said person in drawing an answer
out of thin air without any rational justification or supporting evidence.
James Randi on investigating the "paranormal"
This fallacy refers to the misguided attempt to "explain"
some currently unknown process by simply assuming
that the explanation is ultimately God.

The problem with this fallacy is not with the truth of its claim
(that may or may not be the case),

but with the fact that retreating to God
doesn't actually provide an EXPLANATION
of the nature of the phenomenon in question.

Here is a funny example:

And here is an interesting illustration of this phenomenon:
This fallacy can also occur
when one over-emphasizes evidence
supporting a particular belief, stereotype or prejudice,
while ignoring evidence contradicting it

(this second condition is usually the result of a cognitive bias known as selection or confirmation bias).
Fruit Cake
For the original, check out
A faulty analogy is one in which an invalid conclusion is drawn from a comparison between two apparently similar situations.

The justification of an inference based on analogical reasoning depends on the number, strength and relevance of known similarities and dissimilarities of the items being compared.

If there are
very few known similarities,
or if there are a few known
very great dissimilarities,
then drawing inferences based on the comparison is unjustified.
This fallacy occurs whenever a person
has given up attempting to persuade an audience
about the truth or reasonableness of a position
with arguments and evidence,
and resorts instead to
mere personal attacks
in an attempt to discredit the opposition.
This form of ad hominem fallacy is indirectly used against
some person or group of persons, suggesting that they hold their views mainly because of their special circumstances, vested interests, or some particular motivation.

While this may or may not be true, such circumstances and vested interests are to
the truth or the reasonableness
of a particular position,
which ought to be judged
on its own merits.
This type of argument mistakenly equates
natural with good and unnatural with bad.

In this sort of argument,
nature is taken to be an ideal
or desired state of being,
not simply explaining how things are
but how they should be.

The main problem with this fallacy
is that
one cannot logically derive
a prescriptive value judgment (an ought),
from a descriptive empirical fact (an is).

Another problem is that it is easy
to find plenty of counterexamples
to the natural/good, unnatural/bad equation.
The problem with this analogy is that it's mistakenly comparing
law (one that tells us how something
with a
law (one that tells us how we
ought to
but these are two very different things.

Notice also that the faulty analogy
also produces a fallacy of equivocation,
since there are two different meanings
of the word "law" being used.
Some food for thought
Before you argue that a belief or practice
should be continued or respected
merely because it's a tradition,
ask yourself a few questions:

What is the
for the tradition?

What exactly constitutes the tradition?

Does the tradition entail consequences that go
the point you're trying to make?
What does this mean?
Be careful with your analogies...
Others might want to give them a different use
Richard Dawkins on the double standard afforded to religious beliefs
If there's no reason for it, it's probably nonsense...
Did you notice that while this argument refutes the naturalistic fallacy,
it ends up committing the fallacy
of hasty generalization?

Note: You should be aware that
in ordinary language,
many people misuse the phrase
" that
the question."

What they actually mean is
the question"
(as in "that raises the question of
why we should adopt that policy").

In most cases, the meaning intended can be easily inferred from the context of the discussion, but you should be aware of the distinction.
This black-and-white fallacy is committed
when one omits consideration
of all reasonable alternatives,
and creates what superficially looks
like a dilemma with mutually exclusive options.

In order to prove the fallacy,
one need only point to
some other reasonable alternative
not already considered.

This fallacy is committed whenever one reasons
to a causal conclusion based solely
on one event preceding another in time,
arguing that the first event
must have been the cause of the second.

While it is a
necessary condition
of causal relations that the cause precede the effect,
this is
not a sufficient condition

Post hoc evidence may suggest
the hypothesis of a causal relation,
but such a hypothesis must then be tested
to find if there is indeed such a connection.

(with this, therefore because of it;
also known as
joint effect
or as
mistaking correlation for causation,
confusing cause for effect
(After it, therefore because of it)
Of course, sometimes it does make sense to follow the crowd,
but we have to understand when and why...
Link to the story: http://www.huffingtonpost.co.uk/2013/09/13/nigerian-student-science-prove-gay-marriage-wrong_n_3920879.html
Explanation / Refutation
Warning: Contains strong language.
Check out
for the full clip
Some spurious correlations
A little recap...
But correct spelling, while obviously important, is not enough to guarantee your work is up to par.

Consider the following examples:
Dear Jack,

I want a man who knows what love is. All about you are generous, kind, thoughtful people, who are not like you. Admit to being useless and inferior! You have ruined me. For other men I yearn! For you I have no feelings whatsoever. When we’re apart I can be forever happy. Will you let me be?


Dear Jack,

I want a man who knows what love is all about. You are generous, kind, thoughtful. People who are not like you admit to being useless and inferior. You have ruined me for other men... I yearn for you! I have no feelings whatsoever when we’re apart. I can be forever happy – will you let me be yours?

And remember, punctuation matters too!
Sometimes the term
is applied
to fallacies of relevance and red herrings.

This simply refers to an argument in which
the conclusion does not follow from its premises,
but the expression is primarily used when the gap between premises and conclusion is particularly wide.
Full transcript