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# Critical Reasoning

1. Accident – This fallacy is committed when a reasoner draws the conclusion that some characteristic or
property belongs to a member of a collection or group of things, entities or events only because it is
generally true for that collection or group of things, entities or events. This is the fallacy that happens
when someone treats a general tendency as if it were a categorical claim or an “iron law” that would be
true in each specific instance or case, rather than as a claim that is true in some or most cases, but not
all. In the field of probability there are many logical pitfalls. One is to reason to the probability of
something being true or happening in the future simply from the statistical generality of its occurrence
in the past. But, statistics and probabilities (or “odds”) are not the same thing! If one could easily and
dependably reason to particular conclusions based simply on a general tendency, it would be a lot easier
to make money betting on things like sports than it is! In fact, the simple tendency of a batter to hit a
ball or a team to win its games at a particular statistical rate in the past is not enough in itself to support
specific conclusions about the probability of any particular result in the next at-bat or game. Similarly,
the bare fact that something is true in general for a group or collection is never enough in itself to
establish that the same thing will be true for any single member of the group. Here are some simple
examples of the Accident fallacy:
Whales are fish, because most sea-going creatures with fins are fish, and whales are
sea-going creatures with fins.
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She is a Drexel student, and in general, Drexel students are creative, intelligent, and
energetic. Hence, I expect Anna to be a creative, intelligent, and energetic young woman.
Most of the animals at the zoo have “Property of the Zoo” stamped on them. Since this
penguin is from the zoo, it should have “Property of the Zoo” stamped on it as well.
2. Ad Hominem – This is the common inductive fallacy that occurs when a reasoner offers irrelevant
negative and usually abusive claims about the proponents or supporters of some position as the only
evidence against the position. The Ad Hominem fallacy is commonly known as “name-calling,” and in
politics is a basic ingredient of what has come to be known as “mud-slinging” and “negative” or
“oppositional” campaigning. The Ad Hominem fallacy amounts to arguing that something is a bad idea
for the irrelevant reason that it is promoted or held or was originated by persons the arguer dislikes or
distrusts. The basic mistake of this fallacy is to shift attention away from the real question toward a
different issue.27 But the characteristic feature that makes an argument Ad Hominem is that it draws
attention to some deficiencies of the proponents or supporters of a position and away from the position
itself or its merits. Here are some simple examples of the Ad Hominem fallacy:
Affirmative action programs are bad policies, since people who support them only do so
out of political correctness.
We can confidently dismiss Dr. Inkblot’s position concerning the war seeing as she’s a
Psychology professor. What does she know about issues of war and peace and
international diplomacy?
Nixon’s foreign and domestic policies were certainly wrong-headed and misguided. This
man was arrogant to the point of being paranoid and psychotic, and he couldn’t even
manage to run his own life, let alone the business of the nation during a time of war.
3. Ad Populum – This is the common inductive fallacy committed when someone reasons that
something is true just because everyone or a large number of people have endorsed it. The fact that
even 100% of the population might agree with an opinion or practice doesn’t make right. Large numbers
of people are often wrong, deluded, or ill-informed, the victims of propaganda and misinformation, or
just conformists. The reason that “everybody says so” is so weak, and depends upon so many other
assumptions being true, that it is in itself worthless as a reason that should convince us of anything.
Arguments that are Ad Populum can nevertheless be very persuasive, especially in contexts where it is
possible to play upon the listeners’ pre-existing fears and peer pressure. An important reason why is
that this fallacy involves appealing to the listener’s sense of similarity to and connection with others.
People like to feel that we belong to a larger community in which we are at home. We all tend to feel
anxious and alienated when it seems like everyone is against us, or our views, or that we have been
excluded from society. The Ad Populum fallacy plays on our fears of being regarded as different from
others. The fact that people want to belong and want to be loved by others makes us all susceptible to
the claim that we will be admired if only we buy whatever product the speaker is selling, or adopt the
political perspective they wish us to adopt. Here are some simple examples of the Ad Populum fallacy:
I think you should study Business in college. Everyone knows a degree in Business is
better than one in the Humanities or Liberal Arts. Just ask anybody!
This President has the worst approval poll numbers in history. So, clearly his
performance as President is unacceptable and inadequate.
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There is something wrong about parents adopting children who are ethnically and racially
friends say that this is wrong.
4. Appeal to Ignorance – This common inductive fallacy occurs when someone claims that an idea or
belief is true or false just because there is no clear evidence or good reason to believe otherwise. This
kind of reasoning argues that we should accept that something is the case if it has not been ruled out,
and that we should deny that something is the case if it has not been proven. While it is good advice not
to accept something as true until there is good evidence for it, it is another thing entirely to conclude
that some specific claim or belief is false because there is no evidence that proves it true. Similarly,
although it is good advice not to rule something out as long as there is a possibility that it is true, it is
another thing entirely to conclude that it is true because we haven’t proven it to be false. In either of
these cases the reasonable thing is to withhold judgment and continue to seek more conclusive
evidence in either direction. Here are some simple examples of the Appeal to Ignorance fallacy:
I believe that UFO’s must have visited the earth at some time in history, seeing as no one
has yet been able to prove that they haven’t.
The regime of Saddam Hussein probably had weapons of mass destruction at the time
the US invaded Iraq, seeing as it hasn’t been completely established that it did not have
them.
No one has yet shown conclusively that garlic does not cure cold and flu symptoms,
therefore, I say it does.
5. Appeal to Tradition – This is the fallacy committed when someone argues that because something
has been thought to be true or practiced over a long time, it is for that reason right to think it or do it
now. There are many things that are valuable about traditional beliefs and practices, but to value them
for the simple reason that they are traditional may conceal and protect beliefs and practices that would
not stand up to critical scrutiny. We can easily think of instances in which long-held ideas or practices
turned out to be wrong, or were simply rejected after being accepted for a long time. The Appeal to
Tradition is also problematic because traditional beliefs and practices differ substantially among persons
and groups. So, to argue that someone outside our group’s traditions should adopt a belief or practice
because our group has always done so would be tendentious. Here are some simple examples of the
In our society women have held jobs that have less prestige than men and they have
been paid less for comparable work for as long as anyone can remember. Hence, there
is no good reason why these practices should be seen as wrong or unfair.
I am against the proposal for Wattsamatta U. to develop a football program. Ever since
the school was founded in 1891, our school community has never felt the need to devote
its energy and financial resources to fielding a football team.
There is simply no good reason to consider having an environmentally sustainable and
healthy Thanksgiving celebration this year. Thanksgiving has always been a festival of
over-consumption and a tribute to gluttony and waste at our house and across America.
6. Apples and Oranges Fallacy – A common fallacy directly associated with analogical reasoning is
known as Apples and Oranges. This is the fallacy committed when an argument is based on an analogy
that is weak or irrelevant to the issue the argument is supposed to address. Although two things
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compared in an analogy might really be similar in a few ways, the ways may not matter depending on
what the issue is. And the two things compared may at the same time be quite different in other ways.
For an Analogical Argument to be strong, the two things compared in the analogy must be alike
enough to give strength to the expectation that what has been true in the one case will be true in the
other. The more similar two things are, the stronger the analogy and, in general, the stronger the
argument based on their sameness. But no matter how strong a similarity there is between two things, if
the similarity is beside the point of the question we are trying to answer, any argument based on it is still
going to be weak. So, the premise that asserts the analogy also has to be relevant to the issue the
argument is designed to address. It is reasonable to assume that what has been true in the past will tend
to be a good guide to future expectations about similar things. But the complexity of most “things” we
might want to make arguments about recommends that great care be exercised whenever it is claimed
that two things really are “similar.” It is very easy, especially when we are inclined to trust a speaker or
to accept his or her conclusions anyway, to accept isolated and irrelevant similarities as if they were
relevant and strong. Here are some simple examples of the Apples & Oranges fallacy:
You will have a lot of fun playing badminton with us in Clark Park, since you enjoy playing
volleyball, and volleyball is just like badminton.
Anyone who has operated a lemonade stand understands that the market determines
winners and losers based on the ability to efficiently produce goods inexpensively and
sell them at a profit. Thus, it is obvious what we need to do to fix our broken national
system of health care.
I should be allowed to text, tweet, play video games or do anything else I want while in
class. Being in class is just like being on a bus or a train or in a movie theatre—you pay
for your seat, and you are at liberty to do as you like.
7. Begging the Question – An argument commits the inductive fallacy known as Begging the Question
whenever its premises simply re-state or assume the truth of its conclusion. Such an argument isn’t
really an argument, since it is just re-asserting the conclusion in the premises as if it were self-evident or
supported itself. Arguments that beg the question come in a wide variety of forms. What they share is
the characteristic of reasoning in a circle—instead of advancing reasons for a position, the position is
merely asserted again and again, often using slightly different words, but logically returning to square
one. Thus, Begging the Question is often referred to as “circular reasoning.” Here are some simple
examples of the Begging the Question fallacy:
Non-quantitative methods of study are worthless, because they don’t involve any
measurements using numbers.
Wattsamatta University cannot afford to undertake the registration changes requested by
the Student Council at this time, since doing so would be expensive and inconsistent with
current policies and procedures.
It’s very clear that the time has come to recognize that the only thing to do in Elbonia right
now is to leave right away, and stop all this talk about small, incremental troop
movements, seeing as we now have no choice but to leave immediately and
unconditionally.
8. Composition – This is the common inductive fallacy committed when someone reasons that just
because a property characterizes some or all of the parts or components of an entity or system, the
same property characterizes the system or entity as a whole. It is easy to think of examples of things
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whose properties are not simply reducible to the properties of their parts. The parts or components of
things often mix and blend to create new and different properties than they individually had before they
taste that isn’t simply the tastes of all the ingredients added together. A sports team, a complex living
organism, and a musical ensemble share this feature of being characterized by properties that cannot be
understood as the simple aggregate result of combining the qualities of their parts. This is why it is
sometimes said of an entity that, “the whole is greater than the sum of its parts.” This well-known
expression captures the idea that something more and different arises when the parts come together
and function as an entity or organism. Here are some simple examples of the Composition fallacy:
Each of its members is a fair and wise person, thus the Academic Honesty Committee
will reach fair and wise decisions.
Mary Anne likes the color orange, so I think Mary Anne will like that painting because the
painting has some orange in it.
The new amphitheater is constructed out of lightweight steel beams. The building is
therefore very light.
9. Division – This fallacy is committed when someone reasons that just because some property
characterizes an entity or system as a whole, the same property characterizes some or all of the parts or
components of that entity or system. The fallacy of Division starts with the whole and draws a
conclusion about all or some of its parts. Division is thus the direct opposite of Composition: while the
Composition fallacy moves from the properties of parts to the whole, Division “divides” the whole,
reasoning from properties of the whole to a part or parts. Division is also closely related to the fallacy of
Accident. The difference between them is just that Division starts with a unified whole or organism and
concludes to some claim about a part. By contrast, the fallacy of Accident starts with a collection of
things or a group of individuals about which we have made a generalization, and concludes to some
claim about a member or instance. Here are some simple examples of the Division fallacy:
Of course Carolyn enjoyed her freshman year at the University. She has always said she
is very glad she graduated from the University and enjoyed being a student there.
Moby Dick is one of the greatest novels ever written, thus, Chapter 42, “The Whiteness of
The Whale,” must be one of the greatest chapters ever written.
Spending more and saving less would be good for our troubled economy right now.
Therefore, at this time, more spending and less savings will be good for each individual
household in our economy.
10. Genetic Fallacy – This is the common inductive fallacy committed when someone argues that
something is true about a thing or an idea, practice, or policy just because it was true of its origins or
causes, or at its beginning or its source. The Genetic Fallacy happens because knowing about the origins
and sources of things is often a good starting point for research. But research has to tell us whether or
not there is a strong continuity between the source or origin of something and its present state or
condition, which after all could be entirely different. This fallacy is often confused with the fallacy of
Appeal to Tradition, since both make the mistake of seeing a basis for justifying present practices or
beliefs in the assertion that the practice or belief was supported at some time past. The difference is
that Genetic Fallacy sees the origin or source of a thing as privileged in determining its present
characteristics while the Appeal to Tradition argues from the maintenance of a belief or set of practices
over time. Genetic Fallacy can also look a lot like Division under certain circumstances where what it
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means to ‘come from’ something else is unclear (as in the first example below). Here are some examples
of the Genetic Fallacy:
This perfume has got to be poisonous, so you should stop using it. Here’s why—in my
botany class we examined the plant that the extract used in the perfume comes from, and
that plant is a poisonous plant.
The first governments were associations among humans who were willing to use violence
to defend their power and maintain order. Hence, governments today are just
organizations devoted to the use of violence to maintain order and defend their power
and privilege.
The liberal arts curriculum is a support for elitism and exclusion. It originated in the idea
that people who were not slaves or servants could pursue a wide range of intellectual and
artistic endeavors.
11. Hasty Generalization – A common fallacy associated with statistical reasoning is called Hasty
Generalization. This is the common inductive fallacy committed when a reasoner argues to a conclusion
about a collection or group of things based on a sample that is unrepresentative of the target the arguer
is trying to generalize about. As we saw above, a sample of observations or instances that can
legitimately “speak for” the larger group or target that one is trying to generalize about should be large
and randomly-selected. If not, the result is likely to be a “sweeping generalization,” which can be
especially dangerous precisely because it may really reflect a small sample that one happens to be
working with, but doesn’t represent the group or class one is supposed to be reasoning about, (the
target). A good deal of the thinking that results in ethnic, gender, and racial stereotyping, for example,
reflects this kind of logical mistake. This fallacy is often also called the fallacy of Anecdotal Evidence.
Here are some simple examples of the Hasty Generalization fallacy:
You won’t have a good time if you take the family to the Adventure Aquarium this
summer. I visited there last summer and the ferry ride was choppy and the aquarium was
crowded.
The new migraine drug we have developed will be effective in the general population.
The proof is that a clinical trial that studied twelve Sicilian nuns dramatically diminished
their symptoms in a study that lasted several weeks.
College students today are definitely more concerned with their own financial matters
than world affairs. I know this because in a recent survey of business majors, 75% said
they were more concerned about paying their credit card bills than the state of the world
and the actions of their government.
12. Post Hoc Ergo Propter Hoc – A common fallacy directly associated with causal reasoning is known as
Post Hoc Ergo Propter Hoc. This is the common fallacy committed when an arguer asserts a causal
relationship between two events just because the one preceded the other. Although a cause must
precede its effect, this does not mean that the observation of precedence, even if made repeatedly, is
enough to allow us to conclude that a causal connection exists. As noted above, more is needed to
establish the likelihood of a causal relationship than mere precedence. The most obvious cases of the
Post Hoc fallacy are standard superstitious reactions and the faulty inferences people can make when
they regard as causally connected two events or circumstances which later appear to be “merely a
coincidence.” Here are some simple examples of the Post Hoc fallacy:
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Literacy rates have steadily declined since the advent of television. Clearly television
viewing impedes learning.
He started using drugs just about the time he started seeing that girl. I knew she was a
Since the beginning of commercial nuclear power production in the 1950’s, the rate at
which breast cancers have been diagnosed has steadily increased. Hence the increase
in the incidence of breast cancer must have been caused by nuclear power production.
13. Red Herring – This inductive fallacy consists of providing premises that lead away from the issue or
question at hand by changing the subject or diverting the listener’s attention. This happens whenever
the premises are addressing a question other than the one that appears to have been intended. Here is
an example:
The United States government is a very complex bureaucratic and organizational
structure, and it would be foolish to take everything our leaders tell us at face value.
Consequently, the World Trade Center was brought down by explosives detonated as
part of a U.S. government conspiracy.
As noted above, Ad Hominem reasoning constitutes an evasion or distraction from the issue an
argument is supposed to be about. This makes it a special case of Red Herring. In the following example,
the arguer answers a question about Ecuador policy with an attack on the press whose effect is to
change the subject:
There are many reasons for breaking diplomatic relations with Ecuador at this time. If the
members of the liberal media would stop badgering the President about it and cease their
unpatriotic and unfounded attacks on him, he would be better able to do the American
people’s business, and protect U.S. interests around the world.
Another common and effective tool for diverting attention is the use of so-called “glittering
generalities” as Red Herrings. These are pleasant-sounding words and phrases like “progress,”
“enterprise,” and “the American Dream,” which have strong positive emotional resonance, but which
are frequently used in a vague way so that it is unclear exactly what they refer to. Invoking these kinds
of words and phrases in this manner tends to draw attention away from the question at hand, and
associates the speaker’s position with good feelings and images. Glittering generalities create a vague
good feeling and promise very little. Here is an example of the use of glittering generalities to create a
Red Herring:
In my view, the government acted appropriately and effectively in response to Super
Storm Sandy. Here’s why—at this time the patriotic thing to do is to focus on rebuilding
and healing, not nasty, partisan sniping. That’s the American Way!
14. Slippery Slope – This is the common inductive fallacy committed when an arguer invokes the domino
effect as a kind of scare tactic predicting that calamitous consequences are inevitably going to follow
from an action or choice, which are exaggerated and unsubstantiated by evidence. The “domino effect”
is the notion that a relatively small and seemingly inconsequential event in one place will set in motion a
sequence of causes and effects that eventually will lead to disaster. The Slippery Slope fallacy happens
when there aren’t any good reasons to expect that the predicted calamitous consequences will actually
follow from the small initial step. Here are some simple examples of the Slippery Slope fallacy:
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You had better stay home and study Friday night. If you don’t, then you won’t get an A on
Monday’s exam. If that happens, your grades won’t be good enough to get into the
medical school you want, and then your whole life is likely to be ruined!
If you take too many Philosophy classes, you’ll discover all kinds of interesting things you
won’t get paid for thinking about. That will make it harder for you to preoccupy yourself
with the petty distractions and delusions people need to focus on to stay employed and
make money in our society, leaving you disillusioned, and unemployable. So, don’t take
too many Philosophy classes.
There are good reasons why the University has to raise tuition another 47% this year. If
we don’t have this increase in revenue, we won’t be able to make the payments on the
loans we took out to finance our various building projects. If that happens, we will have
no choice but to default on our loans, sending the University into a desperate financial
tailspin from which it might never recover. Nobody wants that!
15. Straw Man – An argument commits this inductive fallacy when it oversimplifies, exaggerates, or
distorts an opposing or alternative position and argues against the distorted version, rather than against
the real position. It involves presenting the other side of a debate in its weakest and worst possible light
instead of arguing against its strongest version. The Straw Man fallacy thus typically occurs in the
context of disputation and controversy, and amounts to setting up a flimsy version of one’s opposition
so that one can make a show of how easily it is knocked down. The arguer who contends with a Straw
Man instead of his or her real opponent is actually sidestepping the real contest. Anytime you hear
someone characterize a view to which you know the speaker stands opposed, listen carefully for signs
that he or she is presenting something other than that position, especially if it ends up sounding
ridiculous and unappealing. Here are some simple examples of the Straw Man fallacy:
Those who do not support increasing troop levels and the intensity of our struggle with
insurgents in Iraq would be happy if Osama bin-Laden rode into Baghdad as a
conquering hero. Therefore there is no good rationale for considering the withdrawal of
U.S. troops from Iraq.
Majoring in Classical Studies would be a real waste of time, since it revolves entirely
around reading dusty old books written by dead White men on arcane subjects that have
very little relevance to contemporary issues and real-world problems.
It would be a waste of time for us to discuss building a pedestrian bridge over Chestnut
Street to enhance student safety coming and going from the Hans. The Board of
Trustees cannot just snap its fingers and take on a massive design and construction
project between now and the beginning of classes.
16. Unqualified Expert – This is the common inductive fallacy that happens when evidence is provided
by a person or institution invoked as authoritative whose expertise is either not credible or not
independent. As noted above, credible, independent expert testimony adds strength to conclusions, but
the lack of such testimony in itself isn’t a logical reason to deny or reject a claim. Vested interests and
conflicts of interest are potential not automatic sources of bias in argument. Such ties are likely to have
some effect on what people notice and how it is interpreted. But conflicts of interest and vested
interests do not necessarily mean someone or some organization is biased. Remember, being biased
does not mean simply having an opinion or a perspective, it means holding it without regard to what the
evidence seems to show, and perhaps despite reasonable evidence to the contrary. Arguments that
involve rejecting a claim just because it is offered by someone who is not an expert commit the Ad
Hominem fallacy, (described below). Here are some simple examples of the Unqualified Expert fallacy:
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Restrictions on smoking in restaurants are not necessary to protect public health. My
brother is a pharmacist and he says they will make no difference to public health
whatsoever.
I think the proposal to donate Clark Park to the Nature Conservancy should be rejected
because my friends who spend a lot of time playing Frisbee in the Park think it’s a very